Repair of windings of electrical machines. Banding and balancing of rotors and armatures

reservoirs 04.03.2020

reservoirs

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Winding repair technologyelectrical machines

Long-term practice of operating repaired electrical machines with partially replaced windings has shown that such machines, as a rule, fail after a short time. This is caused by a number of reasons, including a violation during the repair of the integrity of the insulation of the undamaged part of the windings, as well as a discrepancy between the quality and service life of the insulation of the new and old parts of the windings. The most expedient when repairing electrical machines with damaged windings is to replace the entire winding with full or partial use of its wires.

1. Stator windings

The manufacture of the stator winding begins with the preparation of individual coils on a template. To correctly select the size of the template, it is necessary to know the main dimensions of the coils, mainly the dimensions of their straight and frontal parts.

It is not difficult to determine the length of the rectilinear part of the coil; it is more difficult to determine the exact length of the frontal part, which depends not only on the winding pitch, but also on the design of the machine being repaired.

The dimensions of the winding coils of repaired machines can be determined by measuring the old winding. However, with this method, it is not always possible to obtain accurate data, and in the case of severe damage, and even more so the complete absence of a winding, it is not applicable at all. Not always required winding data can be found in standard albums. Therefore, in repair practice, it is most acceptable to determine the dimensions of the coil of the repaired machine using the simple calculations below, and then manufacture one or two coils based on the results of the calculation and refine their dimensions in place after laying in the core grooves.

When calculating, first of all, the average length (cm) of the half-turn () is determined by the formula:

where is the length of the active steel package, cm;

The length of the half of the frontal part, including two straight sections, which are a continuation of the grooved part of the coil, and two curved sections, see Fig.

For an approximate determination, it is necessary to first determine the width of the coil φ according to an arc passing through the middle of the grooves in which the coil fits:

where in - step shortening factor;

D- boring diameter, cm;

h- slot height (the “+” sign in brackets is for the stator, the “-” sign for the rotor) .

From the value of f, you can approximately determine the length.

For double layer coil winding

f (3)

where coefficient To taken depending on the number of poles, 2p = 2; 4; 6; eight; K = 1.3; 1.35; 1.45; 1.55 (respectively).

For a single-layer concentric winding, the approximate value is determined by multiplying the results of the calculation from formula (3) by a factor of 1.12.

Specifying the dimensions of the overhang of the end parts of the test coil in place is necessary to ensure the minimum allowable gap between the front parts of the new winding and the end shields of the machine being repaired. This should be done before impregnating and drying the winding. An attempt to change the value of the extension of the frontal parts of the already impregnated and dried winding in the axial or radial direction by padding is unacceptable, as this will lead to a violation of the solidity of the winding and damage to its insulation.

Loose winding coils are wound on simple or universal templates with a manual or mechanical drive.

For manual winding of the coils on the template, both parts of the pads 1 (Fig. 1) of the template are preliminarily separated by a distance determined by the size of the winding, and they are fixed in the cutouts of the disk 3 mounted on the shaft 2.

Rice. 1 Machine for manual winding of coils:

1- template pads

4- revolution counter

5- handle

One end of the winding wire is fixed on the template and, by rotating the handle 5, the required number of turns of the coil is wound.

The number of turns in the wound coil is shown by the counter. 4, mounted on the frame of the machine and connected to the shaft 2. Having finished winding one coil, transfer the wire to the adjacent cutout of the template and wind the next coil. It is advisable to wind the coils from one piece of copper wire d = 1.81 mm (no more) or aluminum d = 2.26 mm (no more): the use of large wires will complicate their laying in the grooves, damage their own insulation and slot boxes. In the absence of wires of the required diameters, the coils are wound with two parallel wires equivalent to the required total cross section.

Manual winding of coils on a simple template requires a lot of labor and time. To speed up the winding process, as well as reduce the number of solder joints, mechanized winding of coils is used on machines with special hinged patterns that allow you to sequentially wind all coils per coil group or for the entire phase.

To wind the coil group on a mechanically driven hinged template, wind the end of the wire into the template 8 (Fig. 2) and turn on the machine.

Rice. 2. Mechanized winding of the coil group:

a- swivel template b-schematic diagram of a mechanical drive; / - mandrel, 2 - clamping nut, 3 - fixing bar, 4 - hinge bar, 5 - pneumatic "cylinder, 6 - broadcast, 7 - band brake, 8 - template, 9 - template hinge mechanism, 10 - automatic stop mechanism of the machine, 11 - electric motor, 12 - machine switch pedal

Having wound the required number of turns, the machine automatically stops. To remove the wound bobbin group, the machine is equipped with a pneumatic cylinder 5, which, through a rod passing inside the hollow spindle, acts on the hinge mechanism 9 of the template. In this case, the heads of the template are shifted to the center and the released coil group is easily removed from the template.

At a number of large electrical repair enterprises, more advanced winding machines are used, which make it possible to fully automate the entire process of winding windings of rotors and stators of electrical machines.

Before winding coils or coil groups, the wrapper must carefully read the winding and settlement note of the electrical machine being repaired.

The note indicates: power, rated voltage and rotor speed of the electric machine; type and design features of the winding; the number of turns in the coil and the number of wires in each turn; brand and diameter of the winding wire; winding step; number of parallel branches in a phase and coils in a group; the order of alternation of coils; the class of insulation used for heat resistance, as well as various information related to the design and method of manufacturing the winding.

Often, when repairing motor windings, it is necessary to replace the missing wires of the required grades and sections with the available wires. For the same reasons, winding the coil with one wire is replaced by winding with two or more parallel wires, the total cross section of which is equivalent to the required one. When replacing the wires of the windings of the repaired electric motors, beforehand (before winding the coils), the fill factor of the groove is checked according to the formula

where n is the total number of wires in the groove;

d- diameter of the insulated wire (on insulation), mm;

S P - sectional area of the groove, mm 2;

S is the total cross-sectional area of \u200b\u200bthe insulation (gaskets, slot box and wedge), mm 2.

The slot filling factor should be within 0.7-0.75. With a coefficient of more than 0.75, it will be difficult to lay the winding wires in the grooves, and less than 0.7, the wires will not fit tightly in the grooves and the power of the electric motor will not be fully used.

Coils of a two-layer winding are placed in the grooves of the core in groups as they were wound on a template. Coils are stacked as follows. The wires are distributed in one layer and put the sides of the coils adjacent to the groove (Fig. 3); the other sides of these coils are left not nested in the slots until the lower sides of the coils are nested in all the slots covered by the winding pitch. The following coils are laid simultaneously with the lower and upper sides. Between the upper and lower sides of the coils in the grooves, insulating gaskets made of electric cardboard bent in the form of a bracket are installed, and between the frontal parts - made of varnished fabric or sheets of cardboard with pieces of varnished fabric glued to them.

Rice. 3. Laying in the grooves of the stator core of the wires of the loose winding coil

When repairing electrical machines of old designs with closed slots, it is recommended that, before dismantling the winding, take its winding data from nature (wire diameter, number of wires in the slot, winding pitch along the slots, etc.), and then make sketches of the frontal parts and mark the stator slots. This data may be necessary when restoring the winding.

The execution of windings of electrical machines with closed slots has a number of features. such machines are made, as a rule, in the form of sleeves made of electric cardboard and varnished cloth.

For the manufacture of sleeves pre-sized. the grooves of the machine produce a steel mandrel 1, which is two counter wedges (Fig. 4). The dimensions of the mandrel must be less than the dimensions of the groove by the thickness of the sleeve 2.

Rice. 4 Method for manufacturing insulating sleeves of electrical machines with closed core grooves: 1-steel mandrel, 2- insulating sleeve

Then, according to the size of the old sleeve, blanks from electric cardboard and lacquered fabric are cut into a complete set of sleeves and their manufacture is started. The mandrel is heated to 80-100 ° C and tightly wrapped with a workpiece impregnated with bakelite varnish. On top of the workpiece, a layer of cotton tape is tightly applied with a full overlap. After the time required for the mandrel to cool to ambient temperature, the wedges are bred and the finished sleeve is removed. Before starting winding, the sleeves are inserted into the stator grooves, and then they are filled with steel knitting needles, the diameter of which should be 0.05-0.1 mm larger than the diameter of the insulated winding wire.

From the coil of the winding wire, a piece of wire is measured and cut off, which is necessary for winding one coil. The use of too long pieces of wire complicates winding, requires more time and often causes damage to the insulation of the wire due to its frequent pulling through the groove.

Pull-winding is labor-intensive manual work; it is usually performed by two winders standing on both sides of the stator (Fig. 5).

Rice. 5. Winding coils of the stator winding of an electric machine with closed core slots

The winding process consists of the operations of pulling the wire through the sleeved grooves, previously cleaned of dirt and remnants of the old insulation, and laying the wire in the grooves and frontal parts. Winding usually starts from the side where the coils will be connected, and is carried out in the sequence below.

The first winder strips the end of the wire at a length exceeding 10-12 cm of the groove length, and then, removing the knitting needle in the first groove, inserts the stripped end of the wire instead of it and pushes it to the exit from the groove on the opposite side of the core. The second winder grabs the end of the wire protruding from the groove with pliers and pulls the wire to its side, and then, removing the knitting needle from the corresponding groove, inserts the end of the elongated wire instead of it at the winding step and pushes it to the side of the first winder. The further winding process is a repetition of the operations described above until the groove is completely filled.

Pulling the wires of the last turns of the coils presents certain difficulties, since it is necessary to drag the wire through the filled groove with great effort. To facilitate the pulling of wires of the PLD, PBD, PLBD brands with fibrous insulation, they are rubbed with talcum powder. In repair practice, wrappers often use paraffin instead of talc. The use of paraffin is not recommended, since the cotton insulation of the wire covered with a layer of paraffin poorly absorbs impregnating varnishes, as a result of which the insulation conditions of the grooved part of the winding wires worsen, which can lead to turn short circuits in the winding of the repaired machine.

When winding the coils, the inner coil is wound first, the front part of which is laid according to the template, and for winding the remaining coils, spacers made of electric cardboard are placed on the wound front part. These gaskets are necessary to create gaps between the frontal parts that serve for insulation, as well as for better blowing of the heads with cooling air during the operation of the machine.

The insulation of the frontal parts. The windings of machines for voltages up to 500 V, intended for operation in a normal environment, are made with cotton tape, with each subsequent layer half-overlapping the previous one. Each coil of the group is wound, starting from the end of the core, adhering to the following order. First, a part of the insulating sleeve protruding from the groove is wrapped with tape, and then a part of the coil to the end of the bend, after which the tape is fixed with an adhesive. The middle of the heads of the group is wrapped with a common layer of tape in full overlap.

The end of the tape is fixed on the head with an adhesive or firmly sewn to it. The winding wires lying in the groove must be firmly held in it. For this, grooving wedges are used, made mainly from dry beech or birch.

Wedges are also made from various insulating materials of appropriate thickness, for example, sheet fiber, textolite or getinaks.

Wedges are made on special machines, one of which is shown in fig. 6.

Rice. 6. Machine for making slot wedges:

1-body, 2-cutter, 3.7-top and bottom plates, 4-diaphragm

chamber, 5 - comb, 6 - return spring, 8 - workpiece.

blank 8 starts under the comb 5, and then, by turning the handle, compressed air is supplied, which, acting on the diaphragm and the system of rods, lowers the comb onto the workpiece. The workpiece is cut during the longitudinal mechanical movement of the milling machine table relative to the rotating cutter 2. For each pass of the table, five wedges are cut, the shape and size of which depend on the shape and size of the cutting parts of the cutter, as well as on the height of the table relative to it. When the cutter leaves the grooves, the comb returns to its original position under the action of spring 6.

The length of the wedge should be 10-20 mm longer than the length of the stator core and equal to or 2-3 mm less than the sleeve length. The thickness of the wedge depends on the shape of the top of the groove and its filling. Wooden wedges must be at least 2 mm thick. To give the wedges moisture resistance, they are boiled for 3-4 hours in drying oil at 120-140 ° C, and then dried for 8-10 hours at 100-110 ° C.

Wedges are hammered into the grooves of small and medium-sized machines with a hammer and a wooden extension, and into the grooves of large machines - with a pneumatic hammer. Having finished laying the coils in the stator slots and wedging the winding, they assemble the circuit. If the winding phase is wound with separate coils, the assembly of the circuit begins with the serial connection of the coils into coil groups.

For the beginning of the phases, the conclusions of the coil groups coming out of the grooves located near the terminal plate are taken. These conclusions are bent to the stator housing and the coil groups of each phase are preliminarily connected by twisting the ends of the wires of the coil groups that have been stripped of insulation.

After assembling the winding circuit by applying voltage, the dielectric strength of the insulation between the phases and to the case is checked, as well as the correct connection of the circuit. To check the correctness of the circuit, the stator is briefly connected to a 120 or 220 V network, and then a steel ball (from a ball bearing) is applied to the surface of its bore and released. If the ball rotates around the bore, the circuit is assembled correctly. This check can also be made using a turntable or a special apparatus. A disk of tin is punched in the center and fastened with a nail at the end of a wooden plank so that it can rotate freely, and then the turntable made in this way is placed in the bore of the stator connected to the network. With the correct assembly of the circuit, the disk will rotate. The most advanced device for checking the correct assembly of the circuit and the absence of turn short circuits in the winding of the machine being repaired is the EL-1 apparatus.

Rice. Fig. 7. Electronic device EL-1 for control testing of windings (a) and its device for detecting a groove with short-circuited turns (b)

Apparatus EL-1 (Fig. 7, a) is designed to detect turn short circuits and breaks in the windings of electrical machines, to find a groove with short-circuited turns in the windings of stators, rotors and armatures, to check the correct connection of the windings according to the scheme, as well as to mark the output ends of the phase windings of electrical machines.

The device has a high sensitivity, which makes it possible to detect the presence of one short-circuited turn for every 2000 turns.

The portable device EL-1 is placed in a metal casing with a carrying handle. On the front panel of the device there are control knobs, clamps for connecting the tested windings or devices for finding a groove with short-circuited turns and a cathode-beam indicator screen. On the rear wall there is a fuse and a block for connecting the cord and connecting the device to the network.

There are five clips on the bottom of the front panel. The far right terminal is used to connect the ground wire, the terminals "Output imp." - for connecting series-connected test windings or an excitatory electromagnet of a device, terminals "Signal.yavl." - for connecting a movable electromagnet of a device or connecting the midpoint of the tested windings. The mass of the apparatus is 10 kg.

The windings are tested by the EL-1 apparatus according to the attached instructions. To detect defects, two identical windings or sections are connected to the apparatus, and then they are fed from both tested windings using a synchronous * switch. periodically voltage pulses on the cathode ray tube of the device: if there are no damages in the windings and they are the same, then the voltage curves on the screen of the cathode ray tube will overlap each other, and if there are defects, the voltage curves will bifurcate.

To identify the grooves in which there are short-circuited turns of the winding, use a device with two U-shaped electromagnets for 100 and 2000 turns (Fig. 7, b). To do this, the coil of a stationary electromagnet (100 turns) is connected to the terminals "Output imp." apparatus, and the coil of a movable electromagnet (2000 turns) - to the terminals “Sign. yavl.", while the middle handle should be set to the leftmost position "Working with the device".

When shifting both electromagnets of the device from groove to groove along the stator bore, a straight or curved line with small amplitudes will be observed on the screen of the cathode-ray tube, indicating the absence of short-circuited turns in the groove, or two curved lines with large amplitudes, turned out with respect to each other and indicating the presence of short-circuited turns in the groove. According to these characteristic curves, a groove with short-circuited turns of the stator winding is found. In a similar way, rearranging both electromagnets of the device along the surface, of a phase rotor or armature of DC machines, they find grooves with short-circuited turns in them.

When performing winding work, along with conventional tools (hammers, knives, pliers, etc.), special tools are also used (Fig. 8), which facilitate such work as laying and sealing wires in grooves, cutting insulation protruding from a groove, bending copper rods anchor windings, etc.

Rice. 8. Wrapper tool kit:

a- fiber plate, b- fiber tongue,

in - reverse wedge, g - corner knife,

d 4- punch, e- hatchet,

f, h- hooks for bending rotor rods

2. Rotor windings

In asynchronous motors with a phase rotor, two main types of windings are common: coil and rod. The methods of winding the windings of the rotors practically differ little from the methods of winding the same stator windings described above. When winding the windings of the rotors, it is necessary to evenly position the frontal parts of the winding to ensure the balance of the masses of the rotor, especially for high-speed electric motors.

In medium and large power machines, the most common are rod two-layer wave windings of rotors. In these windings made of copper rods, it is not the rods themselves that are damaged, but only their insulation due to frequent and excessive heating, during which the slot insulation of the rotors is often damaged.

When repairing rotors with rod windings, the copper rods of the damaged winding are usually reused, so the rods are removed from the grooves in such a way as to save each rod and, after restoring the insulation, put it in the same groove in which it was before disassembly. To do this, the rotor is sketched and records are made for the following winding elements:

bandages- the number and location of bandages, turns and layers of bandage wire, the diameter of the bandage wire, the number of paper clips (locks). and layers, the material of the bandage insulation;

frontal parts- the length of the overhangs, the direction of the bending of the rods, the pitch of the winding (front and rear), transitions (bridges), the grooves of which include the beginnings and ends of the phases;

groove parts- the dimensions of the rod (insulated and non-insulated), the length of the rod within the groove and the total length of the straight section;

isolation- the material, the size and number of insulation layers, the rods removed from the grooves, the groove box, the gaskets in the groove, in the frontal parts, the design of the winding holder insulation, etc.

balancing weights- the number and location of balancing weights;

scheme- a sketch of the complete winding scheme with the numbering of the grooves and an indication of its distinguishing features.

These sketches and notes must be especially carefully made when repairing machines of old designs.

When removing the rods of the rotor windings, it is necessary to unbend the locks of the bandages and remove the bandages, fill (in accordance with the numbering of the grooves in the drawing of the winding diagram) the numbers on the grooves, which include the beginnings and ends of the phases, as well as transition jumpers and remove the wedges from the grooves of the rotor. Next, you need to unsolder the soldering in the heads, remove the connecting collars and clean the rods and collars from the influx of solder.

Special key (see fig. 8, h) it is necessary to unbend the bent frontal parts of the rods of the upper layer from the side of the slip rings, remove these rods from the groove, while on each rod it is necessary to knock out the number of the groove, layer and remove the rods of the lower layer in the same order. Then you need to clean the rods from the old insulation, straighten (straighten) them, removing burrs and irregularities, and clean the ends with a metal brush.

At the end of the operation, it is necessary to clean the grooves of the rotor core, winding holder and pressure washers from insulation residues and check the condition of the grooves. If there are faults, fix them.

The rods extracted from the grooves of the rotor, the insulation of which could not be removed mechanically, are fired in special furnaces at 600-650 °C, preventing the firing temperature from exceeding 650 °C. Insulation from copper rods can be removed chemically by immersing them for 30-40 minutes in a bath with a 6% sulfuric acid solution. The rods taken out of the bath should be washed in an alkaline solution and water, and then wiped with rags and dried. The ends of the rods are tinned with POS 30 solder.

For free from old insulation and straightened rods, the insulation is restored. The new insulation of the rods is impregnated with varnish and dried.

The slot insulation is also restored by inserting gaskets on the bottom of the slots and slot boxes so that they protrude evenly from the slots on both sides of the rotor core. At the end of the preparatory operations, proceed to the assembly of the winding.

The assembly of the rod winding of the rotor consists of three main types of work - laying the rods in the grooves of the rotor core, bending the frontal part of the rods and connecting the rods of the upper and lower rows by soldering or welding.

The rods are put into grooves with only one curved end. The bending of the second ends of these rods is carried out with special keys after being laid in the grooves. First, the rods of the lower row are laid in the grooves, inserting them from the side opposite to the contact rings. Having laid the entire lower row of rods, their straight sections are upset to the bottom of the grooves, and the curved frontal parts - to the insulated winding holder. The ends of the curved frontal parts are firmly tightened with a temporary bandage made of soft steel wire, pressing them tightly against the winding holder. The second temporary wire bandage is wound in the middle of the frontal parts.

Temporary bandages serve to prevent displacement of the rods during further bending operations.

After fixing the rods with temporary bandages, they begin to bend the frontal parts. The rods are bent using two special keys (see Fig. 8, f, h) first step by step, and then along the radius, providing the required axial overhang and their tight fit to the winding holder. To bend the rod, take the key in the left hand (see Fig. 8, g) and put it on the straight part of the rod coming out of the groove of the core with a pharynx. Holding the key in the right hand (see Fig. 8, h), put it on the frontal part of the rod with a pharynx and bring it close to the key (see Fig. 8, g), and then bend it with the key (see Fig. 8, h) rod at the required angle.

The straight parts of neighboring rods do not allow bending the first rods immediately to the required angle, therefore the first rod can only be bent by the distance between the rods, the second - by a double distance, the third - by a triple, and so on until the rods are bent, occupying two or three winding steps, after which you can bend the rod to the desired angle. The last (additionally) bend those rods from which bending was started.

With the help of special keys, the ends of the rods are also bent, on which connecting clamps will then be put on, after which temporary bandages are removed and interlayer insulation is applied to the frontal parts, and gaskets between the rods of the upper and lower layers are placed in the grooves. The phase rotor of an asynchronous electric motor in the process of assembling the rod winding is shown in fig. nine.

Rice. Fig. 9. Phase rotor of an asynchronous electric motor in the process of assembling the rod winding: 1 - rack of the rotary device, 2 - video clip, 3 - lower row of rods, 4, 5 - insulation between top and bottom rows of rods

The described method of bending the winding rods with the help of special keys requires a lot of labor and time. In a number of electrical repair shops, a simple device (Fig. 10) is used to perform this operation, consisting of two plates and a system of levers.

Rice. 10. Device for bending the rods of the rotor winding

The bending of the rod in the fixture is performed in the following sequence. First, a straightened rod with tinned ends is inserted into slot 2 formed by plates 1 and 3, bring to the stop 6, and then by turning the lever BUT out of position I into position II bend the end of this rod to a given angle. Then turn the lever B, moving in an inclined plane from a position I into position II, bend the second corner of the rod, return the levers A and B c starting position II and remove the bent rod from the fixture. The return of the lever to its original position is carried out by the pusher 4, spring-loaded 5.

Upon completion of the laying of the rods of the lower row, they proceed to the installation of the rods of the upper row of the winding, inserting them into the grooves from the side opposite to the slip rings of the rotor. After laying all the rods of the upper row, temporary bandages are applied to the rods, and their ends are connected with copper wire to check the insulation of the winding (the absence of short circuits to the case).

If the insulation test results are satisfactory, continuing the winding assembly process, the ends of the upper rods are bent using techniques similar to the methods of bending the lower layer rods, but in the opposite direction. The curved frontal parts of the upper rods are also fastened with two temporary bandages. After laying the rods of the upper and lower rows, the rotor winding is dried at 80-100 ° C in an oven (or in a drying cabinet) equipped with supply and exhaust ventilation. The dried winding is tested by attaching one electrode from the high-voltage test transformer to any of the rotor bars and the other to a polished core tooth or rotor shaft, and since all bars are connected to each other by copper wire, the insulation of all bars is tested simultaneously.

The final operations for manufacturing a new rotor winding of a repaired machine are connecting the rods, driving the wedges into the grooves and banding the winding.

The connection of the rods is carried out by soldering with solder POSZO with tinned clamps put on the ends of the rods. Clamps can be made of thin strip copper or thin-walled copper tube. In addition, lockable clamps are used, made from a copper strip 1-1.5 mm thick. One end of a lockable collar has. curly protrusion, and another corresponding cutout. When the clamp is bent, the protrusion enters the cutout and forms a lock that prevents the clamp from unbending.

Clamps are put on (according to the scheme) on the ends of the rods, one copper contact wedge is hammered between them, and then the connection is soldered with a POSZO solder with a soldering iron or the ends of the rods of the assembled rotor winding are immersed in a bath of molten solder. In order to save expensive lead-tin solder, the rods are also connected by welding, but this method has a number of disadvantages, for example, it reduces the maintainability of the machine, since the disassembly of the rods connected by welding is associated with large labor costs for separation and cleaning of welded areas. To increase the reliability of machines, the connection of rods by hard soldering is used. The windings of the phase rotors of asynchronous electric motors are connected mainly according to the "star" scheme in this sequence. Of the six free ends of the rods, three are connected together, and the remaining three are led to the slip rings of the rotor.

Upon completion of the assembly and soldering of the winding rods, the rotor shrouding is started. When the rotors rotate, as is known, centrifugal forces arise, tending to bend the frontal parts and throw the winding out of the grooves. The frontal parts of the windings keep wire bandages from bending under the action of centrifugal forces.

The grooved parts of the winding are fixed in the grooves both with bandages and wedges. The method of fastening the winding in the grooves depends on the shape of the groove. With closed, half-closed and half-open grooves, the windings are fastened with wedges made of wood or various solid electrical insulating materials (textolite, plastic, etc.). The windings of the rotors, located in the open grooves of the core, are fixed with wedges and bandages.

The banding of the rotor windings is carried out on special machines with an electric motor drive or on various devices. In the electrical workshops of many enterprises, for the shrouding of the rotor windings, lathes are used in combination with a device for controlled tension of the wound binding wire.

A simple design tensioner, developed and implemented at the Electrosila plant, is shown in fig. eleven.

Rice. 11. Device for tensioning the binding wire when winding the bandages

Its main parts are: base 1, detachable frame, consisting of two cheeks 2, clamping mechanism, consisting of a steering wheel 5, rigidly coupled with a screw 9 and a fixed nut 7, a spring 4 and two pressure discs 3, between which the wire is braked. The bandage wire is threaded through a system of rollers (dashed lines in the figure) and clamped by a handwheel between disks that do not rotate, but move freely relative to each other. Wire tension created by discs; depends on the force of their compression by a spring calibrated with the dial of the dynamometer 6. By moving the screw, they act on the stop of the transmission lever 8 dynamometer, the arrow of which shows the compression force, i.e. wire tension.

In the absence of special devices, the tension of the binding wire is created using a load. To do this, prepare a piece of wire of the required length; Having installed the shrouded rotor in the gantry and temporarily fixed one end of the wire in the area where the extreme turn of the shroud should be located, the rotor is rotated clockwise and the entire shroud is wound around it manually. The second end of the wire is thrown over the block with the load and fixed on the rotor. After that, the rotor is rotated counterclockwise, observing the load. When the rotor rotates, the load, creating tension in the wire, moves along the axis of the rotor from one extreme position to another (along the width of the bandage), laying the coils of wire with the necessary tension.

For shrouding the rotors, tinned steel wire D = 0.8-2 mm is used, which has a high tensile strength.

The entire bandage is wound with one piece of wood fiber, without rations, to avoid swelling on the frontal parts of the winding, the turns of wire are applied from the middle of the rotor to its ends. If there are special grooves on the rotor, the bandage wire and locks should not protrude above the grooves, and in the absence of grooves, the thickness and location of the bandages should be the same as they were before the repair.

Brackets mounted on the rotor must “place over the teeth, not over the slots. In this case, the width of the bracket should be less than the width of the upper part of the tooth. The brackets on the bandages are evenly spaced around the circumference of the rotor; the distance between them but be no more than 160 mm. The distance between two adjacent bandages should be 200-260 mm. The beginning and end of the binding wire 1 (Fig. 12) are closed with two lock brackets 2, which are set at a distance of 10 mm from one another. The edges of the brackets are wrapped around the turns of the bandage and sealed with POS 30 solder.

Rice. 12 Location, turns of the bandage and termination of the ends of the bandage wire: 1 - turns of the bandage wire, 2 - lock brackets

In contrast to bandaging with steel wire, the rotor is heated to 100°C before winding fiberglass bandages around it. The need for preliminary heating of the rotor is due to the fact that when a bandage is applied to a cold rotor, the residual tension in the bandage during its baking decreases more than when the bandage is heated.

The cross section of the fiberglass bandage must be at least 2 times greater than the section of the corresponding wire bandage. The fastening of the last turn of fiberglass with the underlying layer occurs during the drying of the winding during sintering of the thermosetting varnish with which the fiberglass is registered. When shrouding the windings of the rotors with fiberglass, there is no need to use locks, brackets and under-shroud insulation.

3. Anchor windings

The main malfunctions of the armature windings are a breakdown on the body or on the bandage, a short circuit between the turns and sections, and mechanical damage to the rations. When preparing the armature for repair with the replacement of the winding, they clean it of dirt and oil, remove the old bandages and, having unsoldered the collector, remove the old winding, having previously recorded all the data necessary for the repair.

In armatures with micanite insulation, it is often very difficult to remove the windings from the slots. If it is not possible to remove the sections, heat the anchor in the drying cabinet to 70-80°C and maintain this temperature for 40-50 minutes. After that, the sections are removed from the grooves using a thin polished wedge, which is driven between the upper and lower sections to raise the upper sections, and between the lower section and the bottom of the groove to raise the lower ones. The grooves of the armature freed from the winding are cleaned of the remnants of the old insulation, treated with files or steel mandrels, and then the bottom and walls of the grooves are covered with insulating varnish.

In DC machines, template armature windings are most widely used. Insulated wires are used to wind sections of such a winding.

Template winding sections are wound on universal templates, which allow winding, and then stretching a small section without removing it from the template. The stretching of sections of anchors of large machines is carried out on special machines with a mechanical drive. before stretching, the section is fastened by temporarily braiding it with a cotton tape in one layer to ensure its correct formation during stretching.

The coil of template windings (Fig. 13, a) is insulated manually, and at large repair enterprises on special insulating machines. The machine (Fig. 13, b) consists of a tension roller 2, a roller 3 s with insulating tape 1, stop 4, rotating ring 5 and guide rollers 6, installed on the frame 7.

Rice. 13, Insulation of the armature winding coil:

a- coil prepared for insulation,

b- machine coil insulation

The machine is driven by a 0.6 kW electric motor with round belt transmission 8. Having inserted the insulated coil into the machine until it stops, the electric motor is turned on, which drives the ring with the roller mounted on it. 3. The roller runs around the coil (along its cross section) and winds a cotton insulating tape around it. To evenly isolate the entire surface of the coil, it is slowly moved from left to right along a fixed stop 4. The insulated coil is impregnated and dried, after which it is inserted into the grooves of the armature core and fixed in them with wedges.

The armature, prepared for laying the winding coil in its grooves, is shown in fig. 14. When inserting a template coil, it must be ensured that it lies correctly in the groove, i.e., its ends facing the collector, as well as the distance from the edge of the steel core to the transition of the straight (groove) part to the front, must be the same.

Rice. 14. Anchor of a DC machine before laying a template coil in it, winding: 1 - collector, 2 - sectional isolation. from strips of electric cardboard, 3 - core, 4 - groove insulation (boxes)

After laying all the coils with a test lamp, check the correctness of the output of the wires from the grooves, and then attach the wires to the collector plates by soldering with solder POS 30.

Attaching the ends of the armature winding to the collector plates by soldering is one of the most important operations, since poor-quality soldering causes a local increase in resistance and increased heating of the connection area during machine operation.

To perform soldering, an anchor with a collector is preliminarily installed on a stand in an inclined position, so that when soldering, the solder does not flow into the space between the plates, and the armature winding is also protected with several layers of asbestos fabric. Next, put the stripped ends of the winding wires into the slots of the plates, sprinkle with rosin powder, heat the collector to 180-200 ° C with a blowtorch or gas burner and, melting the solder bar with a soldering iron, solder the winding wires to the plates.

The quality of the soldering is checked by an external inspection of the place of soldering, by measuring the contact resistance between adjacent pairs of collector plates, by passing the normal operating current through the armature winding.

On the surface of the collector plates and between. they should not be frozen drops of solder. With well-made soldering, the transition resistance between all pairs of collector plates should be the same: a sharp difference in the direction of increasing transition resistance in any pair of plates will indicate a low soldering quality in this area. When passing through the armature winding for 20-30 minutes of normal operating current, local increased heating should not be observed, indicating unsatisfactory soldering.

4. Pole coils of DC machines

When repairing DC machines, the most difficult operation is the manufacture of new pole coils, which are manufactured on special machines (Fig. 15, a, b). Coils of the main poles are wound on frames or templates, guided by the winding data of the machine being repaired. Frames are made from sheet electric cardboard, and templates are made from wood or sheet steel. A wood pattern is used when winding coils of small machines, and from a steel one - when winding coils of medium and large machines.

a) 6)

Rice. 15. Machines for winding a coil of copper strip (a) and insulating the wound coil (6):I- asbestos tape, 2 - mica tape, 3 - sample, 4 - insulating tape, 5 - pole coil

The winding of the coils of the main poles is performed in the following sequence. The frame or template is manually insulated in height with several layers of micafolium, and then a lead plate insulated with varnished cloth is fixed on it, soldered to the beginning of the winding wire. The frame (template) is installed on the machine and the coil is wound. At the same time, make sure that the wire is laid evenly, without gaps and transitions through the turns. Before winding the last layer of wire, a second output plate is installed on the frame, to which the second end of the coil is soldered with POS 30 solder. The wound coil is dried and impregnated, and then varnished and dried in air for 10 - 12 hours. The finished coil 5 (Fig. 16) is mounted on the pole 4 and fastened with wooden wedges 3.

Rice. 16. Pole coil, put on a pole: 1 - lead plates, 2 - frame, 3 - wedges, 4 - pole, 5 - coil

Pole coils are also made in another way, in which the wire is wound not on a frame or template, but directly on an insulated pole. At the same time, the following sequence of operations is followed. First, the surface of the pole is cleaned and hidden with glyptal varnish. Next, cut off a strip of varnished cloth 80 mm wide and a length equal to the perimeter of the pole, and then glue the varnished cloth so that it is adjacent to the core of the pole by half the width. After that, the core of the pole is insulated, winding it with layers of micafolium and asbestos impregnated with varnish. Each layer of micafolium is ironed with a hot iron and wiped with a clean, dry cloth. Having applied insulation of the required thickness, the overhanging edge of the varnished fabric is folded onto the core and glued onto a flat layer of micafolium.

The lower insulating washer is put on the insulated pole, the coil is wound and the upper insulating washer is put on. After that, the coil is fixed on the pole, wedged with wooden wedges.

Coils of additional poles of small machines are wound with insulated wire, and medium and large ones are wound with bare rectangular bus wire, laying the turns of the coil flat or on edge. At the coil of additional poles, it is not the copper that is damaged, but the insulation, so the repair of the coil is practically reduced to restoring its insulation. The insulation between the turns is asbestos paper 0.3 mm thick, which is cut to the size of the turns in the form of frames and inserted between the turns after winding. The outer insulation of the coil consists of sequentially superimposed layers of asbestos tape and mica tape, fixed with a cotton tape. When re-insulating, the coil is cleaned of old insulation and put on a special mandrel.

Gaskets are prepared from asbestos paper, electric cardboard or micanite. The number of spacers must be equal to the number of turns. The turns of the coil on the mandrel are moved apart, and then put between a layer of bakelite or glyptal varnish. Then the coil is pulled together with a cotton tape and pressed onto a metal mandrel.

The coil is pressed as follows. An end insulating washer is put on the mandrel, a coil is mounted on it and covered with a second washer, and then the coil is compressed. Next, the coil is connected to the welding transformer, heated to 120 ° C, after which, additionally compressing, it is finally pressed, and then cooled in the pressed position on the mandrel to 25-30 ° C and removed from the mandrel. The cooled coil is coated with air-drying varnish and kept for 10-12 hours at 20-25 °C.

The outer surface of the pressed coil is insulated with asbestos, and then with micanite tapes, fixed with a cotton tape, which is then varnished. the finished coil is mounted on an additional pole and fixed on it with wooden wedges.

5. Drying and impregnation of windingsto

Some insulating materials used in windings (electric cardboard, etc.) are able to absorb moisture contained in the environment. Such materials are called hygroscopic. The presence of moisture in electrical insulating materials prevents deep penetration of impregnating varnishes into the pores and capillaries of insulating parts during impregnation of the winding, therefore, the windings are dried before impregnation.

Drying of the windings of stators, rotors and armatures before impregnation is carried out in special ovens at 100-120 °C. Recently, the drying of the windings (before impregnation) began to be carried out with infrared rays, the sources of which are special incandescent lamps. These lamps differ from conventional incandescent lamps in that they have a reflective layer on their inner surface, which contributes to a large return and even distribution of heat.

The dried windings are impregnated in special impregnating baths installed in a separate room equipped with supply and exhaust ventilation and equipped with the necessary fire extinguishing equipment.

Impregnation is carried out by immersing parts of the electrical machine in a bath filled with varnish, so the dimensions of the bath must be designed for the dimensions of the repaired machines. Bathtubs (impregnation of stators and rotors of large electrical machines are burned by a pneumatic lever mechanism, which allows turning the handle of the distributing crane smoothly and effortlessly to open and close the heavy cover.

Windings are impregnated with oil, oil-bitumen and polyester impregnating varnishes, and in special cases silicon-organic varnishes. Impregnating varnishes should have low viscosity and good penetrating power, ensuring deep penetration into all pores of the impregnated insulation; harmful effects on the wires and winding insulation, and they must withstand the operating temperature for a long time, while losing their insulating properties.

The windings of electrical machines are impregnated one, two or three times, depending on the conditions of their operation, the requirements for electrical strength, the environment, the mode of operation, etc. while impregnating the windings, the viscosity and density are continuously checked in the bath, because the lacquer solvents gradually disappear and the lacquers thicken . This greatly reduces their ability to slip into the insulation of the winding wires located in the grooves of the stator or rotor core. It is especially reduced in thick varnish with dense laying of wires in the grooves. Insufficient insulation of the windings under certain conditions can lead to a breakdown of their insulation and an emergency failure of the electrical machine.

Windings, as a rule, are impregnated with BT-980, BT-987, VT-988 varnishes, etc. During high-speed repairs and in emergency cases, the windings are impregnated and coated with quick-drying air-drying varnish, KO-961P, which dries at 20 °C within 4-5 hours and creates a film with significant moisture resistance and high insulating ability.

Coating and impregnating varnishes are selected depending on the specific operating conditions of the electrical machine being dismantled, the environment, the design of the machine, and the insulation class.

Varnishes and solvents are toxic, flammable and therefore must be stored in special rooms at a temperature not lower than 8° and not higher than 25°C. The warehouse where varnishes and solvents are stored must be equipped with ventilation and equipped with the necessary fire extinguishing equipment. The worker must perform all work with solvents and varnishes in canvas gloves, goggles and a rubber apron. Varnishes are diluted in quantities necessary only for current work. Stocks of diluted varnishes are not. do.

The windings of electrical machines after impregnation are dried in special chambers with heated air. According to the method of heating, drying chambers are divided into chambers with electric, gas or steam heating, and according to the principle of heated air circulation - with natural or artificial (forced) circulation. According to the mode of operation, drying chambers of periodic and continuous action are distinguished.

In order to reuse the heat of heated air and improve the drying mode in the chambers, a circulation method is used in which 50-60% of the exhausted hot air returns to the drying chamber. For drying windings at most electrical repair plants and in electrical workshops of industrial enterprises, drying chambers with electrical heating are used.

The drying chamber with electric heating represents. a welded steel frame structure mounted on a concrete floor. The walls of the chamber are lined with bricks and covered with a layer of slag wool. The air supplied to the chamber is heated by an electric heater consisting of a set of tubular heating elements. The power of the heater is 30-35 kW. The chamber is loaded and unloaded by a trolley, the movement of which (forward and backward) can be / controlled from the control panel. The starting and turning devices of the fan and heating elements of the chamber are interlocked so that the heating elements can only be turned on after the fan has started. The movement of air through the heater into the chamber occurs in a closed cycle.

In the first period of the day (1-2 hours after the start), when the moisture contained in the windings quickly evaporates, the exhaust air is completely released into the atmosphere; in the subsequent hours of drying, part of the exhaust air, containing small amounts of moisture and solvent vapors, returns to the chamber. The maximum temperature in the chamber is 200°C, and the useful internal volume is determined by the dimensions of the electrical machines being repaired.

During the drying of the windings, the temperature in the drying chamber and the temperature of the air leaving the chamber are continuously monitored. The drying time depends on the design and material of the impregnated windings, the dimensions of the product, the properties of the impregnating varnish and the solvents used, the drying temperature and the method of air circulation in the drying chamber, and the heat output of the heater.

The windings are installed in the drying chamber in such a way that they are better washed with hot air. The drying process is divided into heating the windings to remove solvents and baking the varnish film.

Determination of suitability of windings

Typical winding damages are insulation damage and electrical circuit integrity failure. The condition of the insulation is judged by indicators such as insulation resistance, insulation test results with increased voltage, deviations of the DC resistance values of individual windings (phases, poles, etc.) from each other, from previously measured values \u200b\u200bor from factory data, as well as by the absence of signs of interturn short circuits in individual parts of the winding. In addition, the evaluation takes into account the total duration of the motor without rewinding and its operating conditions.

Determination of the degree of wear of the insulation of the windings is carried out on the basis of various measurements, tests and assessment of the external state of the insulation. In some cases, the insulation of the winding in appearance and according to the test results has satisfactory results, and the motor, after repair, is put into operation without its repair. However, after working for a short time, the machine fails due to insulation breakdown. Therefore, the assessment of the degree of wear of the machine insulation is a crucial moment in determining the suitability of the windings.

A sign of thermal aging of the insulation is its lack of elasticity, brittleness, tendency to cracking and fracture under rather weak mechanical stresses. The greatest aging is observed in places of increased heating, remote from the outer surfaces of the insulation. In this regard, to study the thermal wear of the winding insulation, it is necessary to open it locally to the full depth. For the study, select areas of a small area located in the areas of the greatest aging of the insulation, but available for reliable restoration of the insulation after opening. To ensure the reliability of the results of the study, there should be several places for opening the insulation.

At the opening, the insulation is examined in layers, repeatedly bending the removed sections and examining their surface through a magnifying glass. If necessary, compare identical samples of old and new insulation from the same material. If the insulation during such tests breaks, peels and multiple cracks form on it, then it must be replaced in whole or in part.

The signs of unreliable insulation are also the penetration of oil contaminants into the thickness of the insulation and the loose fitting of the winding in the groove, in which vibration movements of the conductors or sides of the sections (coils) are possible.

To determine the malfunction of the windings, special devices are used. So, to detect turn short circuits and breaks in the windings of machines, to check the correct connection of the windings according to the scheme, to mark the output ends of the phase windings of electrical machines, the electronic apparatus EL-1 is used. It allows you to quickly and accurately detect a malfunction during the manufacture of windings, as well as after laying them in the grooves; the sensitivity of the device allows you to detect the presence of one short-circuited turn for every 2000 turns.

If only a small part of the windings has malfunctions and damages, then a partial repair is prescribed. However, in this case, it must be possible to remove the defective parts of the winding without damaging the healthy sections or coils. Otherwise, a major overhaul with a complete replacement of the winding is more appropriate.

Repair of stator windings

Repair of stator windings is carried out in cases of insulation friction, short circuit between wires of different phases and between turns of one phase, short circuit of the winding to the housing, as well as breaks or poor contacts in soldered joints of windings or sections. The scope of repair depends on the general condition of the stator and the nature of the fault. After determining the stator malfunction, a partial repair is performed with the replacement of individual winding coils or a complete rewind is carried out.

In the stators of asynchronous motors with a power of up to 5 kW of a single series, single-layer random windings are used. The advantages of these windings are that the wires of one coil are laid in each half-closed slot, the laying of the coils in the slots is a simple operation, and the fill factor of the slot with wires is very high. In the stators of electrical machines with a power of 5-100 kW, two-layer loose windings are used with a half-closed groove shape. For asynchronous motors with power above 100 kW, the windings are made with coils of rectangular wire. The stators of machines for voltages above 660 V windings are wound with rectangular wires.

Rice. 103. Hinged template for winding coils:
1 - clamping nut; 2 - fixing bar; 3 - hinge bar.

The methods of manufacturing and laying in the grooves of the stators are different for windings of round or rectangular wires. Coils of round wire are wound on special templates. Manual winding of coils requires a lot of time and labor. More often, mechanized winding of coils is used on machines with special hinged templates (Fig. 103), with which coils of various sizes can be wound. The same templates allow you to wind all coils in series, designed for one coil group or for the entire phase.

The windings are made of PELBO wires (wire enamelled with oil varnish and covered with one layer of cotton threads), PEL (wire enameled with oil-based varnish), PBD (wire insulated with two layers of cotton threads), PELLO (wire, insulated with oil varnish and one layer of lavsan threads).

Having wound the coil groups, they are tied up with tape and proceed to laying in the grooves. To isolate the windings from the housing in the slots, slot sleeves are used, which are a single-layer or multi-layer U-shaped bracket made of a material selected depending on the insulation class. So, for insulation class A, electric cardboard and varnished cloth are used, for heat-resistant winding - flexible micanite or glass micanite.

Production of insulation and laying soft loose winding of an asynchronous electric motor

The block diagram of the algorithm and the flow chart for the repair of the bulk winding of an asynchronous motor is shown below.

Winding technology:

Cut a set of strips of insulating material according to the dimensions of the winding data. Bend the cuff on the cut strips on both sides. Make a set of groove sleeves.

Clean the stator slots from dust and dirt. Insert the full length slot insulation into all slots.

Cut a set of strips of insulating material and prepare the gaskets to size. Prepare a set of gaskets for the frontal parts of the windings.

Insert two plates into the groove to protect the wire insulation from damage when laying them. Insert a coil group into the stator bore; straighten the wires with your hands and put them into the grooves Remove the plate from the groove Distribute the wires evenly in the groove with a fiber rod. Insert an interlayer insulating gasket into the groove. Set the coil on the bottom of the groove with a hammer (hatchet) With a two-layer winding, place the second coil in the groove.

Use ready-made wedges made of plastic materials (PTEF films, etc.) or make wooden ones. Cut wooden blanks to the size of the winding data. Determine their relative humidity and dry to a relative humidity of 8%. Soak wooden wedges in drying oil and dry.

Insert the wedge into the groove and jam with a hammer.
Cut off the ends of the wedges protruding from the ends of the stator with needle nose pliers, leaving 5-7 mm ends on each side. Cut off the protruding parts of the insulating gaskets.

Insert insulating spacers in the ends of the windings between adjacent coils of two groups of different phases laid side by side.
Bend the frontal parts of the winding coils by 15-18 ° with hammer blows towards the outer diameter of the stator. Follow the smooth bending of the coil wires at the points where they exit the groove.

The procedure for manufacturing insulation and laying winding wires may be different. For example, the manufacture of slot sleeves, interlayer gaskets, the manufacture of wooden wedges can be carried out before laying the windings, and then the work order remains according to this scheme.

In winding manufacturing technology, some generalizations are made in detail.

Rice. 104. Laying and insulation of a two-layer stator winding of asynchronous motors:
slot (a) and frontal parts of the winding (b):
1 - wedge; 2, 5 - electric cardboard; 3 - fiberglass; 4 - cotton tape; 6 - cotton stocking.

Coils of a two-layer winding are placed (Fig. 104) in the grooves of the core in groups as they were wound on a template. Coils are stacked in the following sequence. The wires are distributed in one layer and put those sides of the coils that are adjacent to the groove. The other sides of the coils are inserted after the lower sides of the coils of all slots covered by the winding pitch are inserted. The following coils are laid simultaneously with the lower and upper sides with a gasket in the grooves between the upper and lower sides of the coils of insulating pads made of electrical cardboard, bent in the form of a bracket. Between the frontal parts of the windings, insulating gaskets made of varnished cloth or sheets of cardboard with pieces of varnished cloth glued to them are laid.

Rice. 105. Device for driving wedges into grooves

After laying the winding in the grooves, the edges of the groove sleeves are bent and wooden or textolite wedges are driven into the grooves. To protect the wedges 1 from breakage and protect the frontal part of the winding, a device is used (Fig. 105), consisting of a bent sheet steel of the clip 2, into which a steel rod 3 is freely inserted, having the shape and size of a wedge. The wedge is inserted with one end into the groove, the other into the clip and driven by hammer blows on the steel rod. The wedge length should be 10–20 mm longer than the core length and 2–3 mm shorter than the sleeve length; wedge thickness - not less than 2 mm. The wedges are boiled in drying oil at a temperature of 120-140 C for 3-4 hours.

After the coils are laid in the grooves and the windings are wedged, the circuit is assembled, starting with the serial connection of the coils into coil groups. For the beginning of the phases, the conclusions of the coil groups coming out of the grooves located near the input shield of the electric motor are taken. The conclusions of each phase are connected, having previously stripped the ends of the wires.

Having assembled the winding circuit, they check the dielectric strength of the insulation between the phases and on the case. The absence of turn short circuits in the winding is determined using the EL-1 apparatus.

Replacing a coil with damaged insulation

The replacement of a coil with damaged insulation begins with the removal of the insulation of the inter-coil connections and bandages, which attach the front parts of the coils to the bandage rings, then the spacers between the front parts are removed, the coil connections are unsoldered and the slot wedges are knocked out. The coils are heated by direct current to a temperature of 80 - 90 °C. The upper sides of the coils are raised with the help of wooden wedges, carefully bending them inside the stator and tying them to the frontal parts of the stacked coils with a keeper tape. After that, the coil with damaged insulation is removed from the grooves. The old insulation is removed and replaced with a new one.

If, as a result of turn short circuits, the wires of the coil are burned out, it is replaced with a new one wound from the same wire. When repairing windings from rigid coils, it is possible to save winding wires of rectangular cross section for restoration.

The technology of winding rigid coils is much more complicated than random winding coils. The wire is wound on a flat template, the grooved parts of the coils are stretched to an equal distance between the grooves. Coils have considerable elasticity, therefore, to obtain accurate dimensions, their grooved parts are pressed, and the frontal parts are straightened. The pressing process consists in heating coils lubricated with bakelite or glyptal varnish under pressure. When heated, the binders soften and fill the pores of the insulating materials, and after cooling, they harden and hold the wires of the coils together.

Before laying in the grooves, the coils are straightened with the help of devices. The finished coils are placed in grooves, heated to a temperature of 75 - 90 ° C and upset with light hammer blows on a wooden sedimentary plank. The frontal parts of the coils are also straightened. The lower sides of the frontal parts are tied to the bandage rings with a cord. Gaskets are clogged between the frontal parts. The prepared coils are lowered into the grooves, the grooves are wedged and the inter-coil connections are connected by soldering.

Repair of rotor windings

In asynchronous motors, the following types of windings are used: "squirrel cages" with rods filled with aluminum or welded from copper rods, coil and rod. The most widespread are "squirrel cages" filled with aluminum. The winding consists of rods and closing rings on which fan wings are molded.

To remove the damaged “cell”, melt it or dissolve aluminum in a 50% solution of caustic soda for 2–3 hours. A new “cell” is poured with molten aluminum at a temperature of 750–780 °C. The rotor is preheated to 400-500 °C to avoid premature solidification of aluminum. If the rotor is weakly pressed before pouring, then during pouring aluminum can penetrate between the iron sheets and close them, increasing the losses in the rotor from eddy currents. Too strong pressing of iron is also unacceptable, since breaks of newly poured rods may occur.

Repair of "squirrel cages" from copper rods is most often carried out using old rods. After sawing the connections of the “cage” rods on one side of the rotor, the ring is removed, and then the same operation is performed on the other side of the rotor. Mark the position of the ring relative to the grooves so that the ends of the rods and the old grooves coincide during assembly. The rods are knocked out by carefully hitting the aluminum tamps with a hammer and straightened.

The rods should enter the grooves with a light hammer blow on the textolite lining. It is recommended to simultaneously insert all the rods into the grooves and knock out the diametrically opposite rods. The rods are soldered in turn, preheating the ring to a temperature at which the copper-phosphorus solder easily melts when brought to the junction. When soldering, they monitor the filling of the gaps between the ring and the rod.

In asynchronous motors with a phase rotor, the methods for manufacturing and repairing rotor windings are not much different from the methods for manufacturing and repairing stator windings. The repair begins with the removal of the winding circuit, the locations of the beginning and ends of the phases on the rotor and the location of the connections between the coil groups are fixed. In addition, sketch or record the number and location of bandages, the diameter of the bandage wire and the number of locks; number and location of balancing weights; insulation material, the number of layers on the rods, gaskets in the groove, in the frontal parts, etc. Changing the connection diagram during the repair process can lead to rotor imbalance. A slight imbalance while maintaining the circuit after repair is eliminated by balancing weights that are attached to the winding holders of the rotor winding.

After establishing the causes and nature of the malfunction, the issue of partial or complete rewinding of the rotor is decided. The bandage wire is unwound onto a drum. After removing the bandages, the solderings in the heads are unsoldered and the connecting clamps are removed. The frontal parts of the rods of the upper layer are bent from the side of the contact rings and these rods are taken out of the groove. Clean the rods from the old insulation and straighten them. The grooves of the rotor core and the winding holder are cleaned of insulation residues. Straightened rods are isolated, impregnated with varnish and dried. The ends of the rods are tinned with POS-ZO solder. The groove insulation is replaced with a new one, laying the boxes and gaskets on the bottom of the grooves with a uniform projection from the grooves on both sides of the core. After the completion of the preparatory work, they begin to assemble the rotor windings.

Rice. 106. Laying the coil of the rotor winding:
a - coil; b - an open groove of the rotor with a laid winding.

In a single series A of asynchronous motors with a power of up to 100 kW with a phase rotor, loop two-layer rotor windings from multi-turn coils are used (Fig. 106, a).

When repairing, the windings are put into open grooves (Fig. 106, b). The previously removed rods of the rotor windings are also used. The old insulation is removed from them and new insulation is applied. In this case, the assembly of the winding consists of laying the rods in the grooves of the rotor, bending the frontal part of the rods, and connecting the rods of the upper and lower rows by soldering or welding.

After laying all the rods or finished windings, temporary bandages are applied to the rods, they are tested for the absence of a short circuit to the case; the rotor is dried at a temperature of 80-100 °C in an oven or oven. After drying, the winding insulation is tested, the rods are connected, the wedges are driven into the grooves and the windings are bandaged.

Often in repair practice, bandages are made of fiberglass and baked together with the winding. The cross section of the fiberglass bandage is increased by a factor of 2 to 3 in relation to the section of the wire bandage. The fastening of the end coil of fiberglass with the underlying layer occurs during the drying of the winding during sintering of the thermosetting varnish with which the fiberglass is impregnated. With this design of the bandage, such elements as locks, brackets and under bandage insulations disappear. Devices and machines for winding fiberglass bandages use the same as for winding wire.

Repair of anchor windings

Faults in the armature windings of DC machines can be in the form of a connection between the winding and the housing, interturn short circuits, wire breaks, and soldering of the ends of the winding from the collector plates.

To repair the winding, the armature is cleaned of dirt and oil, the bandages are removed, the connections to the collector are unsoldered and the old winding is removed. To facilitate the extraction of the winding from the grooves, the armature is heated at a temperature of 80 - 90 ° C for 1 hour. To lift the upper sections of the coils, a polished wedge is driven into the groove between the coils, and to lift the lower sides of the coils - between the coil and the bottom of the groove. The grooves are cleaned and covered with insulating varnish.

In the armatures of machines with a power of up to 15 kW with a semi-closed groove shape, bulk windings are used, and for machines of higher power with an open groove shape, coil windings are used. Coils are made of round or rectangular wire. The most widely used template anchor windings are made of insulated wires or copper tires insulated with varnished cloth or mica tape.

Sections of the template winding are wound on a universal template in the form of a boat and then stretched, since it must lie in two grooves located around the circumference of the armature. After giving the final shape, the coil is insulated with several layers of tape, impregnated twice in insulating varnishes, dried and the ends of the wires are tinned for subsequent soldering in the collector plates.

An insulated coil is inserted into the grooves of the armature core. They are fixed in them with special wedges and the wires are attached to the collector plates by soldering with POS-30 solder. Wedges are pressed from heat-resistant plastic materials - isoflex-2, trivolterm, PTEF films (polyethylene terephthalate).

The connection of the ends of the winding by soldering is carried out very carefully, since poor-quality soldering will lead to a local increase in resistance and an increase in the heating of the connection during operation of the machine. The quality of the soldering is checked by inspecting the soldering point and measuring the contact resistance, which should be the same between all pairs of collector plates. Then the operating current is passed through the armature winding for 30 minutes. In the absence of defects in the joints, there should be no increased local heating.

All work on the dismantling of bandages, the application of bandages of wire or glass tape on the anchors of DC machines is carried out in the same manner as when repairing the windings of phase rotors of asynchronous machines.

Repair of pole coils

Pole coils are called excitation windings, which are divided by purpose into coils of the main and additional poles of DC machines. The main parallel excitation coils consist of many turns of thin wire, and the series excitation coils have a small number of turns of heavy gauge wire, wound from bare copper bars laid flat or on edge.

After determining the faulty coil, it is replaced by assembling the coil at the poles. New pole coils are wound on special machines using frames or templates. Pole coils are made by winding insulated wire directly onto an insulated pole, previously cleaned and coated with glyptal varnish. A varnished cloth is glued to the pole and wrapped with several layers of micafolium impregnated with asbestos varnish. After winding, each layer of micafolium is ironed with a hot iron and wiped with a clean cloth. A layer of varnished cloth is glued onto the last layer of micafolium. Having insulated the pole, put on the lower insulating washer, wind the coil, put on the upper insulating washer and wedge the coil on the pole with wooden wedges.

Coils of additional poles are repaired, restoring the insulation of the turns. The coil is cleaned of old insulation, put on a special mandrel. The insulating material is asbestos paper 0.3 mm thick, cut in the form of frames according to the size of the turns. The number of spacers must be equal to the number of turns. On both sides they are covered with a thin layer of bakelite or glyptal varnish. The turns of the coil are moved apart on the mandrel and spacers are inserted between them. Then the coil is pulled together with a cotton tape and pressed. The coil is pressed on a metal mandrel, on which an insulating washer is put on, then the coil is installed, covered with a second washer and the coil is compressed. Heating by means of a welding transformer up to 120 C, the coil is additionally compressed. Cool it in the pressed position to 25 - 30 °C. After removal from the mandrel, the coil is cooled, coated with air-drying varnish and kept at a temperature of 20–25 °C for 10–12 hours.

Rice. 107. Options for insulation of pole cores and pole coils:
1, 2, 4 - getinaks; 3 - cotton tape; 5 - electric cardboard; 6 - textolite.

The outer surface of the coil is insulated (Fig. 107) alternately with asbestos and micanite tapes, fixed with taffeta tape, which is then varnished. The coil is mounted on an additional pole and wedged with wooden wedges.

Drying, impregnation and testing of windings

Manufactured windings of stators, rotors and armatures are dried in special ovens and drying chambers at a temperature of 105-120 °C. By drying, moisture is removed from hygroscopic insulating materials (electrocardboard, cotton tapes), which prevents deep penetration of impregnating varnishes into the pores of insulating parts during winding impregnation.

Drying is carried out in infrared rays of special electric lamps, or using hot air in drying chambers. After drying, the windings are impregnated with varnishes BT-987, BT-95, BT-99, GF-95 in special impregnating baths. The premises are equipped with supply and exhaust ventilation. Impregnation is carried out in a bath filled with varnish and equipped with heating for better penetration of the varnish into the insulation of the wire winding.

Over time, the varnish in the bath becomes more viscous and thicker, due to the volatilization of varnish solvents. As a result, their ability to penetrate into the insulation of the winding wires is greatly reduced, especially in cases where the winding wires are tightly packed into the grooves of the cores. Therefore, when impregnating the windings, the density and viscosity of the impregnating varnish in the bath are constantly checked and solvents are periodically added. The windings are impregnated up to three times, depending on their operating conditions.

Rice. 108. Device for impregnation of stators:
1 - tank; 2 - pipe; 3 - branch pipe; 4 - stator; 5 - cover; 6 - cylinder; 7 - rotary traverse; 8 - column.

To save varnish, which is consumed due to sticking to the walls of the stator frame, another method is used to impregnate the winding using a special device (Fig. 108). Ready for impregnation, the stator with winding 4 is installed on the lid of a special tank 1 with varnish, having previously closed the stator terminal box with a plug. A seal is laid between the end of the stator and the tank cover. In the center of the cover there is a pipe 2, the lower end of which is located below the level of varnish in the tank.

To impregnate the stator winding, compressed air is supplied to the tank through pipe 3 with a pressure of 0.45 - 0.5 MPa, with which the varnish level rises to fill the entire winding, but below the upper edge of the stator frame. At the end of the impregnation, turn off the air supply and hold the stator for about 40 minutes (to drain the remaining varnish into the tank), remove the plug from the terminal box. After that, the stator is sent to the drying chamber.

The same device is also used to impregnate the stator windings under pressure. The need for this arises in cases where the wires are very tightly laid in the stator grooves and during normal impregnation (without varnish pressure), the varnish does not penetrate into all the pores of the insulation of the turns. The pressure impregnation process is as follows. The stator 4 is installed in the same way as in the first case, but it is closed with a lid 5 from above. Compressed air is supplied to the tank 1 and cylinder b, which presses the lid 5 to the end of the stator frame through the installed seal gasket. Rotary traverse 7, mounted on column 8, and the screw connection of the cover with the cylinder make it possible to use this device for impregnating stator windings of various heights.

The impregnating varnish is supplied to the tank from a container located in another, non-flammable room. Lacquer and solvents are toxic and flammable and, in accordance with labor protection rules, work with them should be carried out in goggles, gloves, rubber apron in rooms equipped with supply and exhaust ventilation.

After impregnation, the windings of the machines are dried in special chambers. The air supplied to the chamber by forced circulation is heated by electric heaters, gas or steam heaters. During the drying of the windings, the temperature in the drying chamber and the temperature of the air leaving the chamber are continuously monitored. At the beginning of the drying of the windings, the temperature in the chamber is slightly lower (100-110 °C). At this temperature, solvents are removed from the insulation of the windings and the second drying period begins - baking of the varnish film. At this time, the drying temperature of the windings is increased to 140 ° C for 5-6 hours (for insulation class L). If after several hours of drying the insulation resistance of the windings remains insufficient, then the heating is turned off and the windings are allowed to cool to a temperature that is 10-15 ° C higher than the ambient air temperature, after which the heating is turned on again and the drying process continues.

The processes of impregnation and drying of windings at power repair enterprises are combined and, as a rule, mechanized.

In the process of manufacturing and repairing the windings of machines, the necessary tests of the insulation of the coils are carried out. The test voltage should be such that during the tests defective sections of the insulation are revealed and the insulation of good windings is not damaged. So, for coils with a voltage of 400 V, the test voltage of a coil not dismantled from the grooves for 1 min should be equal to 1600 V, and after connecting the circuit during partial repair of the winding - 1300 V.

The insulation resistance of the windings of electric motors with voltage up to 500 V after impregnation and drying must be at least 3 MΩ for the stator windings and 2 MΩ for the rotor windings after full rewinding and 1 MΩ and 0.5 MΩ, respectively, after partial rewinding. These winding insulation resistance values are recommended based on the practice of repair and operation of repaired electrical machines.

Repair of windings of electrical machines

The winding is one of the most important parts of an electrical machine. The reliability of machines is mainly determined by the quality of the windings, therefore, they are subject to the requirements of electrical and mechanical strength, heat resistance, and moisture resistance.

Preparation of machines for repair consists in the selection of winding wires, insulating, impregnating and auxiliary materials.

The technology of overhaul of the windings of electrical machines includes the following main operations:

winding disassembly;

cleaning the grooves of the core from the old insulation;

repair of the core and the mechanical part of the machine;

cleaning the winding coils from old insulation;

preparatory operations for the manufacture of the winding;

production of winding coils;

insulation of the core and winding holders;

laying the winding in the groove;

soldering winding connections;

fastening of the winding in the grooves;

drying and impregnation of the winding.

Repair of stator windings. The manufacture of the stator winding begins with the winding of individual coils on a template. To correctly select the size of the template, it is necessary to know the main dimensions of the coils, mainly their straight and frontal parts. The dimensions of the winding coils of the dismantled machines are determined by measuring the old winding.

Coils of random stator windings are usually made on universal templates (Fig. 5).

Such a template is a steel plate 1, which, with the help of

the sleeve 2 welded to it is connected to the spindle of the winding machine. The plate has the shape of a trapezoid.

Figure 5 - Universal winding template:

1 - plate; 2 - sleeve; 3 - hairpin; 4 -- rollers

Four studs fixed with nuts are installed in its slot. When winding coils of different lengths, the pins are moved in the slots. When winding coils of different widths, the studs are moved from one slot to another.

In the stator windings of AC machines, usually several adjacent coils are connected in series, and they form a coil group. To avoid unnecessary solder joints, all coils of one coil group are wound with solid wire. Therefore, rollers 4, machined from textolite or aluminum, are put on the studs 3. The number of grooves on the roller is equal to the largest number of coils in the coil group, the dimensions of the grooves must be such that all the conductors of the coil can fit in them.

Coils of a two-layer winding are placed in the grooves of the core in groups, as they were wound on a template. The wires are distributed in one layer and put the sides of the coils that are adjacent to the groove. The other sides of the coils are not placed in the grooves until the lower sides of the coils are laid in all the grooves. The next coils are placed simultaneously with the upper and lower sides.

Between the upper and lower sides of the coils in the grooves, insulating gaskets are installed from electric cardboard bent in the form of a bracket, and between the frontal parts - from varnished cloth or sheets of cardboard with pieces of varnished cloth glued to them.

The manufacture of windings with closed slots has a number of features. The groove insulation of such windings is made in the form of sleeves made of electrical cardboard and varnished cloth. Preliminarily, according to the dimensions of the grooves of the machine, a steel mandrel is made, which consists of two oncoming wedges. The mandrel must be smaller than the groove by the thickness of the sleeve. Then, according to the size of the old sleeve, blanks from electric cardboard and lacquered fabric are cut into a complete set of sleeves and their manufacture is started. The mandrel is heated to 80 - 100 ° C and tightly wrapped with a blank impregnated with varnish. A cotton tape is tightly laid on top of the workpiece with a full overlap. After the mandrel has cooled to ambient temperature, the wedges are spread and the finished sleeve is removed. Before winding, the sleeves are placed in the grooves of the stator, and then they are filled with steel bars, the diameter of which should be 0.05 - 0.1 mm larger than the diameter of the insulated winding wire. A piece of wire is cut from the bay, which is necessary for winding one coil. A long wire complicates winding, and the insulation is often damaged due to its frequent pulling through the groove.

The insulation of the frontal parts of the winding of machines for voltages up to 660 V, intended for operation in a normal environment, is performed with LES glass tape, with each next layer half-overlapping the previous one. Each coil of the group is wound, starting from the end of the core. First, the part of the insulating sleeve that protrudes from the groove is wrapped with tape, and then the part of the coil to the end of the bend. The middle of the heads of the group is wrapped with glass tape in full overlap. The end of the tape is fixed on the head with glue or sewn tightly to it. The winding wires that lie in the groove are held with the help of groove wedges made of beech, birch, plastic, textolite or getinaks. The wedge should be 10 - 15 mm longer than the core and 2 - 3 mm shorter than the groove insulation and at least 2 mm thick. For moisture resistance, wooden wedges are "boiled" for 3-4 hours in drying oil at 120-140 °C.

Wedges are hammered into the grooves of medium and small machines with a hammer and using a wooden extension, and into the grooves of large machines with a pneumatic hammer. Then the winding circuit is assembled. If the winding phase is wound with separate coils, they are connected in series into coil groups.

For the beginning of the phases, the conclusions of the coil groups are taken, which come out of the grooves located near the terminal board. These conclusions are bent to the stator housing and the coil groups of each phase are preliminarily connected, the ends of the wires of the coil groups stripped of insulation are twisted.

After assembling the winding circuit, the dielectric strength of the insulation between the phases and on the case is checked, as well as the correctness of its connection. To do this, use the simplest method - briefly connect the stator to the network (127 or 220 V), and then apply a steel ball (from a ball bearing) to the surface of its bore and release it. If the ball rotates around the circumference of the bore, then the circuit is assembled correctly. Such a check can also be carried out using a turntable. A hole is punched in the center of the tin disc, fixed with a nail at the end of a wooden plank, and then this spinner is placed in the bore of the stator, which is connected to the electrical network. If the circuit is assembled correctly, the disc will spin.

Banding of rotors and anchors

When the rotors and armatures of electrical machines rotate, centrifugal forces arise, tending to push the winding out of the grooves and bend its frontal parts. To counteract centrifugal forces and keep the winding in the grooves, wedging and shrouding of the windings of the rotors and armatures is used.

The application of the winding fastening method (wedges or bandages) depends on the shape of the rotor or armature slots. With an open shape of the grooves, bandages or wedges are used. The grooved parts of the windings in the cores of the armatures and rotors are fixed with wedges or bandages made of steel bandage wire or glass tape, and also with wedges and bandages at the same time; the frontal parts of the windings of the rotors and anchors - bandages. Reliable fastening of the windings is important, since it is necessary to counteract not only centrifugal forces, but also the dynamic forces that the windings are subjected to with rare changes in current. For shrouding the rotors, tinned steel wire with a diameter of 0.8-2 mm is used, which has a high tensile strength.

Before winding the bandages, the frontal parts of the winding are upset by hammer blows through a wooden spacer so that they are evenly located around the circumference. When shrouding the rotor, the space under the shrouds is preliminarily covered with strips of electric cardboard to create an insulating gasket between the rotor core and the shroud, protruding by 1-2 mm on both sides of the shroud. The entire bandage is wound with one piece of wire, without rations. On the frontal parts of the winding, in order to avoid swelling, coils of wire are applied from the middle of the rotor to its ends. If the rotor has special grooves, the bandage wires and locks should not protrude above the grooves, and in the absence of grooves, the thickness and location of the bandages should be the same as they were before the repair. Brackets mounted on the rotor should be placed over the teeth, not over the grooves, and the width of each of them should be less than the width of the top of the tooth. The brackets on the bandages are evenly spaced around the circumference of the rotors with a distance between them of no more than 160 mm. The distance between two adjacent bandages should be 200-260 mm. The beginning and end of the binding wire are closed with two lock brackets 10-15 mm wide, which are installed at a distance of 10-30 mm from one another. The edges of the brackets are wrapped around the turns of the bandage and. soldered with POS 40 solder.

To increase the strength and prevent their destruction by centrifugal forces created by the mass of the winding during the rotation of the rotor, fully wound bandages are soldered over the entire surface with POS 30 or POS 40 solder. . In repair practice, wire bandages are often replaced with glass tapes made of unidirectional (in the longitudinal direction) glass fiber impregnated with thermosetting varnishes. For winding bandages made of glass tape, the same equipment is used as for banding with steel wire, but supplemented with devices c. the form of tension rollers and tape handlers.

In contrast to bandaging with steel wire, the rotor is heated up to 100 °C before winding bandages made of glass tape. Such heating is necessary because when a bandage is applied to a cold rotor, the residual stress in the bandage during its baking decreases more than when a heated one is bandaged. The cross section of the bandage made of glass tape must be at least 2 times greater than the section of the corresponding bandage made of wire. The fastening of the last turn of the glass tape with the underlying layer occurs during the drying of the winding during sintering of the thermosetting varnish with which the glass tape is impregnated. When shrouding the windings of the rotors with glass tape, locks, brackets and underband insulation are not used, which is an advantage of this method.

Balancing rotors and armatures

Repaired rotors and armatures of electrical machines are subjected to static and, if necessary, dynamic balancing as an assembly with fans and other rotating parts. Balancing is carried out on special machines to detect imbalance (imbalance) of the masses of the rotor or armature, which is a common cause of vibration during machine operation.

The rotor and armature consist of a large number of parts and therefore the distribution of masses in them cannot be strictly uniform. The reasons for the uneven distribution of masses are the different thickness or mass of individual parts, the presence of shells in them, unequal, the departure of the frontal parts of the winding, etc. Each of the parts included in the assembled rotor or armature may be unbalanced due to the displacement of its axes of inertia from the axis rotation. In the assembled rotor and armature, unbalanced masses of individual parts, depending on their location, can be summed up or mutually compensated. Rotors and armatures, in which the main central axis of inertia does not coincide with the axis of rotation, are called unbalanced.

Unbalance, as a rule, consists of the sum of two imbalances - static and dynamic. The rotation of a statically and dynamically unbalanced rotor and armature causes vibration that can destroy the bearings and foundation of the machine. The destructive effect of unbalanced rotors and armatures is eliminated by balancing them, which consists in determining the size and location of the unbalanced mass. Unbalance is determined by static or dynamic balancing. The choice of balancing method depends on the required balancing accuracy, which can be achieved with the existing equipment. With dynamic balancing, better results of imbalance compensation (less residual imbalance) are obtained than with static balancing.

To determine the imbalance, the rotor is unbalanced with a slight push. An unbalanced rotor (anchor) will tend to return to a position in which its heavy side is at the bottom. After the rotor stops, mark with chalk the place that is in the upper position. The reception is repeated several times to check whether the rotor (armature) always stops in this position. Stopping the rotor in the same position indicates a shift in the center of gravity.

In the place reserved for balancing weights (most often this is the inner diameter of the pressure washer rim), test weights are installed, attaching them with putty. After that, the balancing procedure is repeated. By adding or decreasing the mass of loads, the rotor is stopped in any, arbitrarily taken position. This means that the rotor is statically balanced, i.e. its center of gravity is aligned with the axis of rotation. At the end of balancing, the test weights are replaced with one of the same section and mass, equal to the mass of the test weights and putty and the part of the electrode reduced by the mass, which will be used for welding the permanent load. Unbalance can be compensated for by drilling out an appropriate piece of metal from the heavy side of the rotor.

More accurate than on prisms and disks is balancing on special scales. The balanced rotor is mounted with the shaft journals on the frame supports, which can be rotated around its axis by a certain angle. By turning the balanced rotor, the highest indication of the indicator J is achieved, which will be provided that the center of gravity of the rotor is located.

By adding an additional load to the load - a frame with divisions, the rotor is balanced, which is determined by the indicator arrow. At the moment of balancing, the arrow is aligned with the zero division.

If the rotor is rotated by 180, its center of gravity will approach the swing axis of the frame by a double eccentricity of the displacement of the center of gravity of the rotor relative to its axis. This moment is judged by the lowest reading of the indicator. The rotor is balanced a second time by moving the weight frame along a ruler with a scale calibrated in grams per centimeter. The magnitude of the imbalance is judged by the readings of the scale of the scales.

Static balancing is used for rotors rotating at a speed not exceeding 1000 rpm. A statically balanced rotor (armature) may have a dynamic imbalance, therefore rotors rotating at a frequency above 1000 rpm are most often subjected to dynamic balancing, in which both types of imbalances are simultaneously eliminated - static and dynamic.

Having secured a constant load, the rotor is subjected to test balancing and, with satisfactory results, is transferred to the assembly department for assembling the machine.

Assembly and testing of electrical machines Assembly is the final stage of the repair of an electrical machine, during which the rotor is connected to the stator using end shields with bearings and the rest of the machine is assembled. As a rule, the assembly of any machine is carried out in the reverse order of disassembly.

The assembly of the machine is carried out in such a sequence that each installed part gradually brings it closer to the assembled state and at the same time does not cause the need for alterations and repetition of the operation.

Technological sequence of the main assembly

The assembly of the DC machine P-41 (Fig. 6) is carried out as follows. They put the excitation coils on the main poles, install the poles with the coils in the frame 16 according to the markings made during disassembly, and fasten them with bolts. They check the distance between the pole pieces with a template, the distance between opposite poles with a shtihmas.

Figure 6 - DC machine P-41

They put coils on additional poles 13, insert the poles with coils into the frame 16 according to the marking made during disassembly, and fasten them with bolts. The distance between the pole pieces of the main and additional poles is checked with a template, and the distance between opposite additional poles is checked with a pin. Connect the coils of the main and additional poles according to the wiring diagram. The polarity of the main and additional poles is checked, as well as the amount of overhang of the winding 12 located in the core 14 of the armature. The fan is mounted on the shaft 7 according to the notes made during disassembly. Lay grease in the labyrinth grooves. Put on the shaft inner covers 2 and 20 bearings. The ball bearings are heated in an oil bath or by induction and mounted on the shaft using a tool. Lubricate the bearings with grease. The anchor is inserted into the frame using the device. Assemble the traverse 6 together with the brush holders on the fixture and grind the brushes. The traverse with brush holders is screwed to the bearing shield 5 and the brushes are lifted from the brush holder sockets. The rear bearing shield 18 is pushed onto the ball bearing, the anchor is lifted by the end of the shaft and the bearing shield is pushed onto the frame lock. Screw the bolts of the bearing shield into the holes of the end of the frame, without tightening them to failure. The front bearing shield 5 is pushed onto the ball bearing 3. The anchor is lifted and the bearing shield is inserted into the frame lock. Screw the bolts of the bearing shield into the holes of the end of the frame, without tightening them to failure. Check the ease of rotation of the armature, gradually tightening the bolts of the bearing shields. Put on the cover 4 of the ball bearing and tighten the covers 4 and 2 with bolts. Lay grease in the labyrinth grooves. Put on the cover 19 of the ball bearing and fasten the covers 19 and 20 with bolts. Check the ease of rotation of the armature by rotating it by the end of the shaft. Lower the brushes onto the collector. Check the distance between the brushes of different fingers along the circumference of the collector and the shift of the brushes along the length of the collector. Check the distance between the collector and the brush holders. Clamps 7 are assembled on a plate 9 in a box 8 and capacitors 10 are attached to it. The assembled clamp plate is installed on the front end shield 5. Electrical connections are made according to the diagram. Check with probes the distance between the armature and the poles. Lead to the clamps of the power wire from the network. Carry out a trial run of the machine. During the running-in process, the operation of the brushes and bearings is checked. Brushes should work without sparks, bearings - without noise. After finishing the run-in, close the collector hatches with covers. Disconnect the power wires and close the terminal box with a lid. They hand over the assembled car to the master or the controller of the quality control department.

When performing assembly work, the electrician must remember that the rotor of the electric motor, held in a central position by the magnetic field of the stator, must be able to move (“run”) in the axial direction. This is necessary so that the rotor shaft, at the slightest displacement, does not erase the ends of the bearings with its sharpening and does not cause additional forces or friction of the mating parts of the machine. The values of the axial run, depending on the power of the machine, should be: 2.5 - 4 mm with a power of 10 - 40 kW and 4.5 - 6 mm with a power of 50 - 100 kW.

All machines after repair check the heating of the bearings and the absence of extraneous noise in them. For machines with a power of over 50 kW at a speed of more than 1000 rpm and for all machines with a speed of more than 2000 rpm, the magnitude of the vibration is measured.

The gaps between the active steel of the rotor and the stator, measured at four points along the circumference, must be the same. The dimensions of the gaps at diametrically opposite points of the rotor and stator of the asynchronous electric motor, as well as between the midpoints of the main poles and the armature of the DC machine, should not differ by more than ± 10%.

Testing of electrical machines. In repair practice, the following types of tests are mainly encountered: before the start of repair and during it to clarify the nature of the malfunction; newly manufactured machine parts; collected after the repair of the machine.

Tests of the machine assembled after repair are carried out according to the following program:

checking the insulation resistance of all windings relative to the housing and between them;

checking the correctness of the marking of the output ends;

measurement of winding resistance to direct current;

checking the transformation ratio of asynchronous motors with a phase rotor;

conducting an idling experiment; overspeed test; test of interturn insulation; dielectric strength test.

Depending on the nature and extent of the repairs performed, sometimes they are limited to performing only a part of the listed tests. If tests are carried out before repair in order to identify a defect, then it is sufficient to carry out part of the test program.

The program of control tests of asynchronous motors includes:

1) external inspection of the engine and measurements of air gaps between the cores;

2) measurement of the insulation resistance of the windings relative to the body and between the phases of the windings;

3) measurement of the ohmic resistance of the winding in the cold state;

4) determination of the transformation ratio (in machines with a phase rotor);

5) testing the machine at idle;

6) measurement of no-load currents by phases;

7) measurement of starting currents in squirrel-cage motors and determination of the starting current ratio;

8) test of electrical strength of coiled insulation;

9) testing the dielectric strength of insulation relative to the housing and between phases;

10) conducting a short circuit test;

11) heating test when the engine is running under load.

The control test program for synchronous machines includes the same tests, with the exception of paragraphs 4, 7 and 10.

Control tests of DC machines include the following operations:

external inspection and measurement of air gaps between the armature core and the poles;

measurement of insulation resistance of windings relative to the housing;

measurement of ohmic resistance of windings in a cold state;

checking the correct installation of brushes on neutrals;

checking the correct connection of the windings of the additional poles with

checking the consistency of the polarities of the coils of series and parallel excitations;

checking the alternation of polarities of the main and additional poles;

testing the machine at idle;

test of electrical strength of coiled insulation;

test of dielectric strength of insulation relative to the housing;

heat test with the machine running under load.

Operating conditions of electrical machines. The conditions under which electrical machines operate. p.s., and first of all, traction engines are very heavy. Unlike permanently installed machines, they are subject to environmental influences, dynamic impacts from the side of the rail track and operate under conditions of widely and sometimes sharply changing current and voltage values.

Despite the measures taken, moisture and dust get into the machines from the environment. Moisture penetrates into the pores of the insulation of the windings of machines, which leads to a decrease in its electrical strength, creates conditions for the occurrence of its electrical or thermal breakdown, and leads to its accelerated aging. In combination with low temperatures, moisture contributes to the formation of frost and icing of the collector and brush apparatus, which leads to increased sparking under the brushes. Increased sparking also occurs from contamination of the collector and brush apparatus with dust entering the machine through leaks in hatches and with cooling air.

The ambient temperature can reach up to -40 °С in winter and up to +50 °С in summer. A high temperature impairs the cooling of electrical machines, contributes to their excessive heating, and a low one causes thickening of the lubricant in the bearings, sweating of machines during the installation of electric power. p.s. at the depot.

When passing roughnesses of the way wheel pairs e. p.s. perceive significant dynamic forces (especially at high speeds). These shocks, partly smoothed out by the spring suspension system, are transmitted to the traction motors. They are most sensitive for traction motors with axial suspension, almost half of the mass of which is not sprung.

From the action of dynamic forces in the elements of machines, cracks, fractures, increased production of rubbing surfaces, increased sparking on the collector, weakening of the joints can occur.

The voltage in the contact wire, and therefore the voltage supplied to the traction motors (and other electric machines), may differ from the nominal value (/nom by 10-12%. In some cases (for example, during regenerative braking), the voltage at the terminals of the traction motors can reach up to 1.25 b t u - The voltage on the traction motors associated with the boxing wheelsets increases markedly.When the current collector is detached from the contact wire, the voltage on the traction motors sharply decreases, and during lightning discharges, its sharp increase.

Any voltage deviation from the nominal value worsens the operation of the traction motor and reduces its traction properties. But the increased voltage is especially dangerous, which can cause potential sparking on the collector and the formation of an all-round fire, breakdown of the insulation of windings, wires, insulation of brush holder brackets, output cables.

When starting or moving along a long lift of heavy trains or when driving with an incomplete number of traction motors operating on a locomotive, the currents in them can significantly exceed their permissible values. Such even short-term overloads can cause increased sparking under the brushes, disrupt commutation, and under certain conditions lead to the formation of an all-round fire on the collector.

An all-round fire can also occur as a result of a rapid increase in current during transient processes occurring in traction motors. The most dangerous are transients resulting from the formation of an all-round fire on an adjacent parallel-connected engine or during a breakdown of the arm of the rectifier installation. No less dangerous are the modes of full voltage shock on a previously de-energized traction motor, for example, when the voltage is reapplied to the motor at the moment when the main handle of the driver's controller is not returned to the zero position.

The operation of electrical machines with currents exceeding the permissible values also leads to their excessive heating, which accelerates the aging of the insulation and limits the full use of their power.

When the wheel pair is boxed, the frequency of rotation of the armature of the traction motor increases sharply. In this case, large centrifugal forces arise, which can cause damage to the shafts of anchors of traction motors, flexible couplings, fans, weakening or damage to anchor bandages. In addition, with an increased frequency of rotation of the armature, sparking under the brushes noticeably increases, the switching of the machine worsens, and conditions are created for the possible occurrence of an all-round fire on the collector. At the moment of restoration of the coupling of the boxing wheelset, the frequency of its rotation (and, consequently, the frequency of the engine armature associated with it) instantly decreases. In this case, the kinetic energy of the rotating armature turns into a blow transmitted to the gear, armature shaft, bearings and other engine elements, causing their increased wear and sometimes breakage.

Statistics have shown that about 30-40% of failures e. p.s. in operation is associated with malfunctions that occur in electrical machines. In order to improve their reliability, the Rules for the repair of traction motors and auxiliary machines of electric rolling stock TsT 2931 (hereinafter referred to as the Repair Rules) provide for appropriate preventive measures and establish a specific procedure and timing for their implementation.

Thus, the Repair Rules provide for the repair of traction motors and auxiliary machines of three types: depot, factory I volume (medium) and factory II volume (capital), and also establishes the frequency of their implementation. At the same time, the possibility of deviating from the established network-wide overhaul runs by 20% in both directions is simultaneously stipulated in order to make it easier for plants and depots to plan repairs more evenly throughout the year. The Main Directorate of the Locomotive Economy of the Ministry of Railways was granted the right to change the terms of repair for certain types of electric machines.

When repairing electrical machines, it is not allowed to replace their main components, therefore, bearing shields, axle boxes of motor-axial bearings, anchor bearings, traverses and other parts are marked. It is desirable to install the anchor in its own skeleton. These requirements are mandatory, as they provide the maximum reduction in labor costs while maintaining the necessary characteristics and parameters of the electric machine after assembly.

All repaired or new parts are checked, tested and presented for acceptance to the master or receiver of locomotives before being installed on the machine.

Each electrical machine released from repair is subjected to control tests in accordance with state standards and the requirements of the Rules for the repair of traction and auxiliary electrical machines e. p.s.

Preliminary preparation of cars for disassembly. After disassembling the wheel-motor unit, the gears are pressed from the shaft of the traction motor of the electric locomotive, and the flange of the elastic coupling is pressed from the shaft of the traction motor of the electric train, using mechanical, pneumatic or oil pullers for this.

Rice. 3.1. Preparing the motor shaft for gear removal

The least degree of possible damage to the landing surfaces of the gear, half-coupling and shaft is provided by oil strippers. However, their use requires preliminary special preparation of the shafts (Fig. 3.1). An annular open groove 3 is made on the neck 4 of the shaft in the middle, the seating surface, slightly not reaching the keyway 2 with its ends. The center hole of the shaft is connected to the groove 3 by channel 5. decreases, and it is easily removed from the shaft.

Then they remove the caps of the motor-axial bearings, take out the bearing shells and padding, remove the remaining oil from the internal surfaces of the cylinder with a rag soaked in gasoline.

Rice. 3.2. A two-chamber machine for external washing and drying of traction motors before disassembling the haul and caps and installing the caps in their original places (but without liners and padding).

Taken from e. p.s. electrical machines and, first of all, traction motors are usually heavily contaminated (during cleaning, up to 15-20 kg of various wastes are removed from the engine, including about 10-12 kg of grease and oil from motor-anchor and motor-torio-axial bearings). Such contamination makes it difficult to identify defects during inspection and leads to a decrease in the quality of subsequent repairs.

The traction motor is cleaned before installing it at the first position of the disassembly production line.

The engine is pre-cleaned from the outside by hand using scrapers and rags. For final cleaning, the engine is washed in special washing (one- or two-chamber) machines.

A two-chamber washing machine (Fig. 3.2) consists of two hermetically sealed chambers. In chamber 1, the engine is washed with hot (80-90 ° C) water 9, which is supplied by pump 1 to a rotating shower device 2 from drive 5. To prevent moisture from getting inside the engine, all ventilation and other openings in the frame are carefully closed with special plugs and covers, and a special branch pipe 3 is attached to the place of the cover of the upper collector hatch, through which air is supplied to the engine from the fan 4, creating excess pressure inside it. closed door 7 for 15-20 minutes, dry it with a stream of air heated from the air heater 6.

The frequency of rotation of the shower and drying devices is 2 rpm. Both cameras can work simultaneously.

The cleaned machine is installed in position 1 of the repair production line (Fig. 3.3), where it is carefully inspected.

Inspection to identify external defects is carried out visually. At the same time, the numbers of the skeleton are checked,

Rice. 3.3. Production line for repair of traction motors:

1 - disassembly line; II - impregnating department; III - assembly line; IV - anchor repair line; 1, 17 - fault positions; 2- disassembly position; 3 - blowing chamber; 4- tilter; 5-position of the repair of the mechanical part; 6, 23 - transport trolley; 7- welding post; 8 - position for checking the electrical strength of insulation; 9 - assembly position; 10 - position of installation of brush holders; II - engine assembly position; 12- stand for testing the engine at idle; 13- testing station; 14- engine anchor; 15 - purge chamber; 16- tilter; 18 - balancing machine; 19- machine for soldering cockerels of the collector; 20, 22, 26, 28 - drives; 21, 27 - positions, respectively, repair and check the electrical part of the armature; 24, 25 - machines for grinding and pathing of collectors of bearing shields and caps of motor-axial bearings.

Then the electrical parameters of the machine are measured, the axial run-up of the armature, the runout and wear of the collector, the radial clearances of the anchor bearings and the runout of the outer rings are determined.

To perform the above measurements, repair position 1 is equipped with the necessary measuring instruments, a static converter with a lead column and an induction heater for removing the inner bearing rings and labyrinth rings.

The insulation resistance of traction motors is measured with a megohmmeter at 2.5 kV. (To eliminate additional error, the insulation resistance should be measured with megohmmeters at the appropriate voltage.)

When measuring insulation resistance, the beginning (or end) of the main pole circuit is connected to the beginning (or end) of another circuit - additional poles and anchor winding. To these conclusions connect the clamp "L" of the megohmmeter. Its second clamp "3" is connected to the machine body. During the measurement process, it is necessary to ensure that the output ends of the controlled windings do not touch the floor or the motor housing, otherwise the instrument readings will be incorrect. For serviceable traction motors, the insulation resistance must be at least 5 MΩ. If it turns out to be less, you should measure the resistance of individual circuits (main and additional poles, armature windings) and identify the damaged area, keeping in mind that the decrease in resistance could be caused by moisture or malfunction of the brackets, intercoil connections.

The insulation resistance is measured before washing the motor.

The insulation resistance of auxiliary machines must be at least 3 MΩ. Methods for checking and identifying defective places in insulation for auxiliary

5 is. 3.4. Installing an indicator to measure collector pressure

Rice. 3.5. Manifold runout tester

Rice. 3.6. The measurement of the collector output by the template of the winding machines is the same as for the traction motors.

The active resistance of the windings of electrical machines is usually measured with an MDb (or UM13) bridge and compared with the value set for a machine of this type. An increase in active resistance can be caused by defects in the pole coils, the melting of cables in cartridges or lugs, a break in the cores of output cables or inter-coil connections and a breakdown in contact in these connections.

To identify the cause of the increase in resistance, the suspect winding of the machine is connected to a static converter and a current is set in it equal to twice the value of its clock mode current. The defective place is detected by touch by increased heating.

Then, when the engine rotates under a voltage of 220-400 V without load, the operation of the anchor bearings, engine vibration, collector beats and the operation of the brush apparatus are checked.

Anchor bearings are checked by their heating and by ear when the engine armature rotates at a frequency of about 700-750 rpm for 5-10 minutes in each direction. A serviceable bearing should work without crackling, clicking, seizing and in the idle mode of the machine should not overheat relative to the ambient temperature by more than 10 ° C.

The vibration of the engine is also checked when it is idling at a speed of 700 rpm. Vibration is measured with a BP-1 handheld vibrograph. The place of application of the vibrograph to the motor housing can be any. If the vibration of the engine is more than 0.15 mm, the armature must be balanced.

The runout of the collector is measured by indicator 1 (Fig. 3.4), which is brought to the collector 4 through the collector hatch and fixed with a clamp 2 on the edge of the frame 3. The runout is measured along the middle part of the working length of the collector and at a distance of 10-20 mm from its outer cut. If it exceeds the maximum permissible value, then the collector must be turned.

The runout of the collector can also be measured using a device (Fig. 3.5), the body 1 of which is fixed on the brush holder bracket. By moving slider 2 to the working part of the collector, indicator 3 is set to zero and the beat is determined during rotation of the collector.

The development (wear) of the working part of the collector can also be measured using this device. To do this, the slider is first taken to the non-working part of the collector, the indicator is set to zero, and then, with the collector stationary, the slider is moved along the entire working part of the collector and the highest output value is fixed on the indicator.

In the absence of the described device, the development can be measured with a template or a feeler gauge and a ruler.

The template (Fig. 3; 6) is installed on the collector 2 and held by hand so that the block 1 of the device is located strictly parallel to the collector plates, and its end coincides with the end of the collector. By rotating alternately the heads of micrometers 3, the production is determined at two points along the length of the collector.

To determine the output with a probe and a ruler (Fig. 3.7), the ruler 2 is installed with a narrow edge on the collector plate 3 and the gap between the lower edge of the ruler and the working surface of the plate is measured with probe 1 along its entire length. Such measurements are made in several places around the circumference of the collector.

The commutation of the machine is evaluated by the degree of sparking* under the brushes. If, during a visual assessment, the sparking under the brushes turns out to be more than g / g points (see p. 156), and no defects are found in the brush-collector assembly, then a thorough check of the magnetic system of the machine, its individual components and switching adjustment is necessary.

The radial clearances of the anchor bearings are checked with feeler gauges on a stationary machine. To do this, remove the outer covers and labyrinth rings of the shield bearings and check the gap between the roller and the inner ring of the bearing in its lower part with a feeler gauge. For traction motors of most types, it should be in the range of 0.09-0.22 mm.

Rice. 3.7. Determining the development of a collector using a ruler and a feeler gauge

The runout of the outer rings of the bearings is a consequence of their misalignment when installed on engines. Such distortions lead to a significant increase in stresses at the edge of the raceway, increased wear and damage to the cages, to radial or axial pinching of the rollers, and sometimes to the destruction of the bearings.

It is possible to detect the distortion of the rings with a special device developed by VNIIZhT. The device (Fig. 3.8) has a ring 4, which is put on the motor shaft 5 until it stops in the inner ring of the bearing and is fixed on it with three centering screws 6. A stand 2 with an indicator 3 is fixed on the ring. The indicator rod 3 should rest with its end against the outer ring bearing 1.

To measure the vertical skew, the device is fixed on the shaft and

Rice. 3.8. Installation for measuring the misalignment of anchor bearings

set the indicator in the upper position to zero. Then the indicator is rotated relative to the shaft by 180° and the runout of the end face is determined (taking into account the sign of the deviation of the arrow). In the same way, the beat is determined in the horizontal plane. The beat value is defined as the maximum difference in the indicator readings. For a correctly installed bearing, the outer ring end runout should not exceed 0.12 mm.

The axial run of the anchor is measured with an indicator. To do this, the anchor is shifted to the stop in one direction, and on the opposite side, an indicator is fixed on a special stand and pressed against the end of the armature shaft or box (on engines of electric locomotives ChS2) so that the head arrow is at zero. Then the anchor is moved all the way to the other extreme position. The deviation of the indicator needle will indicate the axial run. For traction motors with straight and helical gears, it should be no more than 0.2-0.8 and 5.9-8.4 mm, respectively, for auxiliary machines - 0.6-0.15 mm.

Air gaps between the cores of the poles and the armature of the machine are checked with probes. Clearances should not exceed the values established by the Repair Rules for machines of this type.

Otherwise, the magnetic symmetry of the machine will be violated, its characteristics will change, and the switching stability will decrease. Inadmissible deviations in the values of air gaps during the repair of the machine must be eliminated, and when it is tested, a thorough debugging of the switching should be carried out.

The results of the inspection of electrical machines and the measurements taken are entered into a special log for later use in determining the required amount of their repair, after which the engine is transferred to its disassembly position 2 (see Fig. 3.3).

Dismantling of electrical machines. Electric machines are dismantled on flow-conveyor lines, and in their absence - at specialized workplaces equipped with the appropriate equipment and tools.

Traction motors of domestic electric locomotives are dismantled in a vertical position. With the help of a trolley of a lifting and transport installation (or a crane), the engine is installed on a disassembly stand with the manifold down.

When performing any operations related to turning the engine from a horizontal to a vertical position, it should be remembered that in this case, the anchor bearing receives shock from the anchor, is loaded by its full weight, and all this load is perceived mainly by the shoulders of the bearing rings and the ends of the rollers. These forces can be especially large with significant axial runs of the anchor in the skeleton. Therefore, any tilting operation of electric motors must be carried out without jerks and with the utmost care to avoid damage to the bearings.

Collector hatch covers, ventilation grids are removed from the engine, the supply cables are disconnected from the brush holder brackets, the labyrinth sealing rings, rings, bearing shield covers are removed and the brushes are removed from the brush holders. Labyrinth rings are removed in a hot state with an electromagnetic puller. After removing the labyrinth rings, the bearing shield covers are installed in their places. Using a ratchet, the bolt of the brush holder traverse lock is unscrewed, the lock is rotated 180°, the locking device bolts are loosened by three or four turns, and the traverse is compressed through the lower inspection hatch, leaving a gap of no more than 2 mm at the cut site.

Using a pneumatic wrench, the bearing shield fastening bolts are unscrewed from the side opposite to the manifold, the bearing shield is pressed out using a hydraulic press and transported to the anchor bearing press or installed in a special shipping cassette. When pressing out the shields, they must not be skewed in the neck of the skeleton, as this can lead to damage to the seating surfaces.

An eye is screwed onto the armature shaft (or screwed in if the shaft has an internal thread under the eye), hooked to it with a crane hook, smoothly and strictly vertically so as not to damage the collector and bearing, the anchor is removed from the frame and transported to the accumulator of the anchor repair production line.

Labyrinth and thrust bushings, as well as the inner rings of the anchor bearings, are left on the armature shaft and pressed from it only if they need to be repaired or replaced.

Then the engine frame is turned over by 180°, the second bearing shield is pressed out, the brush holders and brackets are removed, or the traverse together with the brush holders is removed from the frame using a special grip and crane.

To press out the outer rings of the anchor bearings, a steel ring 5 is installed between the base plate 1 (Fig. 3. 9) and the bearing shield 2, the height of which is slightly greater than the height of the bearing ring, and the inner diameter is 3-4 mm larger than its outer diameter. The press force P is transmitted to the bearing ring 4 through the steel disk 3, which ensures uniform force distribution around the circumference of the bearing ring.

It is possible to remove the cardan shaft from the armature of the AL-4846eT engine of the ChS2 electric locomotive only after the anchor box chamber is freed from grease. Therefore, these engines are disassembled in a horizontal position. First, they remove the covers of the collector hatches, ventilation grids, disconnect the current-carrying wires and remove the brushes from the brush holders. Then the bearing shields are pressed out, the traverse is removed, the oil chamber of the anchor box is opened, the oil is drained from it, the cardan shaft with the coupling is removed, and only after that, using a special tool - mounting bracket 3 (Fig. 3.10)

Rice. H.9.. Pressing out the bearing shield from the traction motor frame, remove the anchor 2 from the traction motor frame 1.

Traction motors of electric trains are also dismantled in a horizontal position.

Removed on the production line, bearing shields, covers, sealing rings, traverses with brush holders, as well as axle boxes of motor-axial bearings are transported to specialized areas where they are repaired. The repaired components and parts are transferred to the production line for assembling traction motors, and the frame is transferred to the next position of the frame repair line for purging and cleaning its inside.

Auxiliary electrical machines are dismantled, as a rule, in a horizontal position. With a large amount of repair, it should also be carried out on conveyor lines.

Before dismantling, the machines are cleaned, purged and inspected.

Rice. 3.10. Removing the motor armature AL = 4846eT from the frame using a bracket

Given some design features of individual auxiliary machines, the order of their disassembly may differ. Thus, fan motors are often performed in conjunction with control generators (for example, an NB-430 electric motor with a DK-405 control generator). When disassembling them, the skeleton of the generator is first removed. To prevent the removed frame from falling on the generator anchor, it is preliminarily picked up with a crane hook. Similarly, the skeleton of the control generator installed on the NB-453 phase splitter is also removed.

Then, the nut securing the generator armature sleeve is rolled off the armature shaft, the press cup of the armature pressing device is screwed into the sleeve and, by rotating the head of the device, the armature is pressed from the motor shaft. To hold the removed anchor, it is also pre-hung on the crane hook.

If the control generator is connected to the fan motor using a V-belt drive, then during disassembly, the transmission casing and belts are first removed, and then the bolts securing the generator tides to the motor frame are unscrewed and the generator is removed.

When disassembling a motor-compressor, the engine of which does not have a second bearing shield, first remove the traverse or brush holders, disconnect the skeleton of the electric motor from the body and, supporting it with rope slings, carefully remove it from the anchor. Then unscrew the nut that secures the gear to the armature shaft, and remove the anchor.

The sequence of disassembly of motor-generators also depends on the design of their frames. If the frame is detachable, then first remove its upper half, then remove the anchor with bearing shields, remove the brush holder traverses and the brush holders themselves. At the same time, they notice where and how many distance rings it has installed. These rings must be installed when the machine is reassembled after repair, so as not to disturb the previously carried out adjustment of the bearings.

Pulleys or half-couplings are pressed from electric motors P11, P21 and DMK, collector hatch covers are removed, brushes are removed, terminal box covers, outer bearing covers are removed and, applying light blows with a hammer through a wooden gasket along the edges of the bearing shield, the shield is removed from the frame. The anchor is removed, bearings are pressed from it. On the front bearing shield, the bolts securing the traverse are unscrewed and removed.

At the voltage divider, the control generator is first removed (this operation is performed in the same way as when removing the generator from the fan motor shaft), the fan is removed, the brush holder wires are disconnected, the voltage divider is placed with the shaft end on the generator side up, the bearing shield is pressed out and behind the eye with the help of cranes pull out the anchor. Then the skeleton of the voltage divider is set in a horizontal position and the second bearing shield is pressed out. The anchor removed from the frame is placed on the rack and the bearing is pressed from it with a screw tie.

For three-phase asynchronous motors, the protective nets are removed, the oil lines are unscrewed, the bolts securing the bearing shield to the frame from the side of the free end of the shaft are unscrewed, and it is removed using the forcing bolts. The second bearing shield is removed in the same way.

To prevent possible damage to the stator and rotor windings, when removing the rotor, it is lifted and a pressboard 0.3-0.4 mm thick is placed under it. Then a lever is put on the free end of the rotor shaft, lifted with a crane or hoist so that it can move freely inside the stator, the rotor is removed from the machine and laid on wooden blocks. Similarly, having previously removed the speed relay, the NB-455A phase splitter is disassembled.

For asynchronous electric motors AP-81-4, a fan impeller is removed with a special device, and for electric motors AP-81-6, a half-coupling is removed with a screw press. Then remove the bearing caps, press the bearing shields. The rotors are removed from the stators along with the bearings. Bearings are pressed and transferred to the roller compartment.

Safety rules for dismantling electrical machines. Most demolition operations involve the use of cranes, hoists and other lifting equipment. Mooring electrical machines or their individual elements is allowed only by specially trained persons who have the appropriate certificate. Before using a crane or hoist, make sure that the frames, cables and slings are in good condition. Machines or parts moved by cranes must be raised above the floor to a specified height, and unauthorized persons must not be in the crane field.

Cleaning of elements of electrical machines. Depending on their design and the materials used in them, it is performed differently. So, the skeletons and anchors of the machines are first cleaned of dust and other contaminants by blowing them in the purge chamber with compressed air. In order not to damage the insulation, the hose tip should not be brought closer than 150 mm to it. In a number of depots, special chambers are used (Fig. 3.11). In them, the armature 1 of the machine is placed on roller bearings 2 and, when blown, rotates by an electric drive (not shown in the figure), which transmits torque to the armature through a rubberized pressure roller 3. Compressed air is supplied through the air duct 4 with nozzles that provide directional blowing of the armature. The entire installation is enclosed by a casing, which is connected on one side to the foundation on hinges, allowing it to be tilted. When installing or removing the anchor on the supports, it is thrown back, turning around the hinge axis 5. To extract dust, the chamber is connected by an air duct to the ventilation system.

Rice. 3.11. Scheme of the blowing chamber for the anchors of electrical machines

After blowing, the anchor and the frame are subjected to manual cleaning, wiping them with technical napkins or rags soaked in gasoline (when wiping insulation) or kerosene (when cleaning metal elements). Chemical methods can also be used to clean anchors. The anchor is installed in a special chamber, rotated at a frequency of about 30 rpm and a washing composition heated to 90 ° C is fed to it under a pressure of about 150 kPa (15 kgf / cm 2).

The washed anchor is placed on a trolley and fed into the drying oven (Fig. 3.12). Having installed the trolley 8 with an anchor in the furnace chamber 7, the door 9 is closed, the fan motor 5 is turned on. The air supplied to the fan rotor 6 from the chamber through the air ducts 1 is again fed into the chamber. At the same time, the mechanical energy of air moving in rather narrow lower and upper air ducts 1 at a speed of up to 25 / "m / s, turns into thermal energy. mode Usually drying is carried out for no more than 15 hours at a temperature of about 120 ° C. Specific drying modes are taken separately for machines of various types, depending on the class of insulation used in them.

Rice. 3.12. Scheme of the furnace for drying anchors

Bearing shields, their covers, axle boxes of motor-axial bearings and other parts of electrical machines made of ferrous metals and not having elements of leather or rubber are boiled in baths with an alkaline solution, washed in warm water and dried. Motor-anchor bearings are washed in a special washing machine with a soapy emulsion heated to a temperature of 90 ° C for 25-30 minutes. Then these bearings are wiped with technical wipes and washed with gasoline or white spirit with the addition of 7% industrial oil grades 12, 20 or 30.

4-6. SOLDERING OF WINDINGS, COLLECTORS, BANDAGES

The connection of conductors by soldering is carried out using solder. According to the melting temperature, solders are divided into soft (tin - lead) with a melting point of up to "230 ° C and hard (copper - silver) with a melting point of 700 ° C and above. There is also an intermediate group of solders. From among the soft tin-lead solders, solders of grades POS-30-POS-90 (the number indicates the percentage of tin) with a melting point of 180 ° C. Good results are obtained by soldering with pure tin (melting point of 230 ° C. However, due to the scarcity of this metal, soldering with pure tin is carried out only in especially

For anchor		For anchor

more responsible electrical machines in the presence of elevated temperatures.

Cadmium-zinc-silver solders (PKDC Sr 31) with a melting point of 250 ° C are used for soldering bandages of machines with class H insulation, and lead-silver solders (PSSR 2.5) with a melting point of 280 ° C are used for soldering collectors of these machines.

Of the solid ones, silver solders (P Sr 45-70) with a melting point of 660-730 ° C and copper-phosphorus (PMF7, MF-3) with a melting point of 710-850 ° C are used. A number of requirements are imposed on solders: they must in molten form it is good enough to penetrate into the gaps between the surfaces to be soldered, i.e., have sufficient fluidity, should not soften at temperatures that are as close as possible to the melting temperature, and provide sufficient mechanical strength of soldering at these temperatures. The place of soldering should not be fragile. The soldering should have a sufficiently low electrical resistance and, in addition, over time, this resistance, as well as mechanical performance, should not deteriorate due to oxidation and aging.

It should be noted that solders with a high lead content are more prone to oxidation, and copper-phosphorus solders give slightly more brittle compounds than silver ones.

In order for the solder to give a strong connection to the surfaces, in addition to their cleanliness, it is necessary that they do not have an oxide film on them. At the soldering temperature, the surfaces of any metal are covered with such a film. Fluxes are used to destroy the oxide film: rosin for soft rations and borax for hard ones. Etching of surfaces to be soldered with acid when soldering current-carrying parts in electrical machines is not allowed, since acid destroys insulating materials.

Rosin can be used in solid form or in the form of an alcohol solution. Borax is used in the form of a powder or an aqueous solution. Soldering is done with a hot lamp or a soldering iron. To speed up soldering, it is desirable to use electric soldering irons. For hard soldering, electrically heated tongs (Fig. 4-20) and graphite sponges are used,

Collectors and bandages of all machines, stator and rotor tires and connections for machines insulated according to class A with low operating temperatures are soldered with soft solders.

Purely tin solder is recommended for soldering collectors and bandages of critical machines, in which significant overloads are possible. For normal machines, soldering of collectors and bandages can be carried out with POS-30-POS-60 solder with 30-6% tin content (GOST 1499-42).

Rice. 4-20. Welding pliers.

The following are soldered with hard solder: tires (rods) of windings of machines with high overheating and insulated according to the B-H class, uninsulated windings of short-circuited rotors, damper cages, etc. Copper busbars are also connected with hard solder during the winding of coils. Thin wires are soldered with soft solders to avoid overburning.

Soldering technology soft solders involves the following operations: 1) cleaning the surface of the place of soldering; 2) heating the place of soldering to a temperature at which the solder melts from touching the place of soldering; 3) abundant smearing with rosin; 4) the introduction of a solder stick by pressing it to the gap between the surfaces to be soldered; 5) removal (with a rag) of excess solder when hot; 6) cooling and washing off the remains of rosin with alcohol.

For a better connection of soldered surfaces, their preliminary tinning is recommended.

Collector soldering it is made in an inclined position so that the tin does not flow over the cockerels. Warming up the collector with a blowtorch must be done very carefully so as not to let go of the plates. The winding is then closed with asbestos cloth or

cardboard. For small collectors, it is enough to heat the cockerels with a soldering iron.

The same applies to soldering the wires into the tape cockerels (Fig. 4-21). The slot in the plate, the cockerel and the end of the winding wire must be pre-tinned.

The best results are obtained by soldering the collectors in the bath. In this case, the anchor is installed vertically with the collector down. The end part of the cockerels is placed on an asbestos gasket lying on the side of the steel ring. The ring and the collector are heated by electric heating to a temperature of 250 ° C, after which the cockerels are abundantly smeared with rosin and molten tin or solder is poured into the groove between them and the side of the ring.

With this method of soldering, good penetration of tin into all places to be soldered is ensured.

Tin, of course, should not be poured above the level of the cockerels so that it does not flow into the winding.

To perform soldering according to the specified method, the repair shop must have a heating unit and a set of replaceable rings for different diameters of the collectors.

Very convenient (especially in repair conditions) is the method of heating cockerels when soldering collectors, according to which the collector is covered with a copper clamp or wire that provides good contact with the plates. One end from the welding transformer is led to this clamp, and the other end to a soldering iron, which is a copper rod with a graphite lining, fixed in an insulating material handle. By touching the graphite lining to the cockerel, it is heated to the desired temperature.

Rice. 4-21. Soldering cockerels.

Soldering Tires a two-layer winding provides for preparation, i.e., covering the tires with a bracket and wedging them with a copper wedge (Fig. 4-22). The rotor is given a slight tilt to prevent the tin from flowing into the winding.

If the tires have a large cross section, and the bracket is long, then to facilitate the soldering of the entire surface, slots or round holes are made in the bracket (Fig. 4-"23). Soldering can only be done well

Rice. 4-22. Training

rods rotary

windings for soldering.

Figure 4-23. Bracket with holes.

but in the event that there are no voids inside the bracket with splinted tires. Otherwise, the solder will leak out and the soldering will be fragile.

Bandage soldering after winding them, it consists in uniformly soldering with a thin layer of tin adjacent turns of the binding wire, so that a continuous belt is formed, as it were. In this case, there should not be places where the tin is applied in such a thick layer that it closes the turns of the binding wire.

Soldering wires hard solder is produced in the following sequence: 1) preparation of the ends; 2) warming up to a dark red-crimson color; 3) sprinkling with borax until the ends of the wire are completely covered with a layer of molten borax; 4) further heating until the solder melts, after which it is necessary to stop heating; 5) inspection and filing of the place of soldering; checking its bending strength. Solder in the form of a leaf is laid between the ends of the wire. For rectangular copper of large cross section, the joint is made obliquely (angle 65 °). The ends are inserted into the clamps and one is fixed tightly, the other is loose. The soldering point is heated with a blowtorch, autogenous burner or electric tongs (Fig. 4-20).

Tire soldering can be produced with similar tongs with carbon jaws. Solder in the form of a leaflet is placed under the bracket, which is compressed by pliers. For the short time required to melt the solder, the current is switched on.

Good results are obtained by soldering with solder from phosphorous copper MF-3 (melting point 720-740 ° C).

The surfaces to be soldered are cleaned with sandpaper and squeezed with electric tongs. By turning on the current, the place of soldering is heated to 750-800 ° C, and at the same time the edges of the surfaces to be soldered are smeared with solder. Due to the high fluidity of this solder, it is distributed over the entire surface. For better spreading of the solder, it is desirable to position the solder plane inclined or vertically.

Soldering aluminum wires and busbars complicated by the fact that aluminum is highly susceptible to oxidation. For soldering aluminum wires between themselves and with copper wires, special solders have been developed [L. 1] with a melting point of 160-450 ° C, containing mainly zinc, tin and additives: aluminum, copper, silver, cadmium.

Aluminum can be soldered with tin using an ultrasonic soldering iron. Such a soldering iron has, in addition to the heater, a winding powered by a current of 20,000 hz, enclosing a special alloy steel core. The working end of the soldering iron at the same time makes high-frequency vibrations that destroy the oxide strips.