Technological map for repairing windings of an asynchronous motor. Drawing up a technological map for the overhaul of an AIR63A2 asynchronous electric motor of a hydraulic pump. The relevance of the course work lies in knowledge of the rules for organizing technical maintenance

Current repairs are carried out to ensure and restore the functionality of the electric motor. It consists of replacing or restoring individual parts. It is carried out at the installation site of the machine or in the workshop.

Frequency of execution current repairs electric motors is determined PPR system. It depends on the installation location of the engine, the type of machine or machine in which it is used, as well as on the duration of work per day. Electric motors undergo routine repairs mainly once every 24 months.
When carrying out routine repairs, the following operations are performed: cleaning, dismantling, disassembling and fault detection of the electric motor, replacing bearings, repairing terminals, terminal boxes, damaged areas of the frontal parts of the winding, assembling the electric motor, painting, testing at idle and under load. For DC machines and electric motors with a wound rotor, the brush-commutator mechanism is additionally repaired.

Table 1 Possible malfunctions of electric motors and their causes

Current repairs are carried out in a certain technological sequence. Before starting repairs, it is necessary to review the documentation, determine the operating time of the electric motor bearings, and determine the presence of unrepaired defects. A foreman is appointed to carry out the work, preparations are made necessary tools, materials, devices, in particular lifting mechanisms.

Before dismantling begins, the electric motor is disconnected from the network, and measures are taken to prevent accidental voltage supply. The machine to be repaired is cleaned of dust and dirt with brushes and blown with compressed air from the compressor. Unscrew the screws securing the terminal box cover, remove the cover and disconnect the cable(s) supplying power to the motor. The cable is pulled out, observing the required bending radius, so as not to damage it. Bolts and other small parts are placed in a box, which is included in the set of tools and accessories.

When dismantling the electric motor, it is necessary to make marks with a core to fix the position of the coupling halves relative to each other, and also to mark which hole in the coupling half the pin fits into. The gaskets under the paws should be tied and marked so that after repair each group of gaskets is installed in its place, this will make it easier to center the electric machine. Covers, flanges and other parts should also be marked. Failure to do so may result in the need for repeated disassembly.

Remove the electric motor from the foundation or workplace using the eye bolts. The shaft or bearing shield must not be used for this purpose. Lifting devices are used for removal.

Disassembling the electric motor is carried out in compliance with certain rules. It begins with removing the coupling half from the shaft. In this case, manual and hydraulic pullers are used. Then the fan casing and the fan itself are removed, the bearing shield mounting bolts are unscrewed, the rear bearing shield is removed with light blows of a hammer on an extension made of wood, copper, aluminum, the rotor is removed from the stator, the front bearing shield is removed, and the bearings are dismantled.

After disassembly, the parts are cleaned with compressed air using a hair brush for the windings and a metal brush for the casing, bearing shields, and frame. Dried dirt is removed with a wooden spatula. The use of a screwdriver, knife or other sharp objects is prohibited. Defects of an electric motor involve assessing its technical condition and identifying faulty components and parts.

When a mechanical part is defective, the following is checked: the condition of the fasteners, the absence of cracks in the housing and covers, wear of the bearing seats and the condition of the bearings themselves. In DC machines, a serious component that requires comprehensive consideration is the brush-commutator mechanism.

Here, damage to the brush holder, cracks and chips on the brushes, wear of the brushes, scratches and gouges on the surface of the commutator, protrusion of micanite gaskets between the plates are observed. Most malfunctions of the brush-collector mechanism are eliminated during routine repairs. If there is serious damage to this mechanism, the machine is sent for major repairs.

Malfunctions of the electrical part are hidden from the human eye, they are more difficult to detect, and special equipment is needed. The number of damage to the stator winding is limited by the following defects: open circuit, short circuit of individual circuits to each other or to the housing, turn short circuits.

A break in the winding and a short circuit to the housing can be detected using a megohmmeter. Turn short circuits are determined using the EL-15 apparatus. The broken rods of the squirrel-cage rotor are found using a special installation. Malfunctions that can be eliminated during routine repairs (damage to the frontal parts, breakage or burning of output ends) can be determined with a megohmmeter or visually; in some cases, an EL-15 apparatus is required. When carrying out defect detection, the insulation resistance is measured to determine the need for drying.

Direct current repair of the electric motor is as follows. If a thread is broken, a new one is cut (threads with no more than two cut threads are allowed for further use), the bolts are replaced, and the lid is welded. Damaged winding terminals are covered with several layers of insulating tape or replaced if their insulation along its entire length has cracks, peeling or mechanical damage.

If the frontal parts of the stator winding are damaged, air-drying varnish is applied to the defective area. Bearings are replaced with new ones if there are cracks, chips, dents, tarnish and other faults. The bearing is seated on the shaft by preheating it to 80...90°C in an oil bath.

Installation of bearings is carried out manually using special chucks and a hammer or mechanized using a pneumohydraulic press. It should be noted that due to the introduction of unified series of electric machines, the volume of repairs of the mechanical part has sharply decreased, since the number of varieties of bearing shields and covers has decreased, it became possible to replace them with new ones.

The procedure for assembling the electric motor depends on its size and design features. For electric motors of sizes 1 - 4, after pressing the bearing, the front bearing shield is installed, the rotor is inserted into the stator, the rear bearing shield is put on, the fan and cover are put on and fastened, after which the coupling half is installed. Next, according to the scope of routine repairs, cranking at idle, coupling with the working machine and testing under load are carried out.

Checking the operation of the electric motor at idle or with an unloaded mechanism is carried out as follows. After checking the operation of the protection and alarm, perform a test run, listening for knocking, noise, vibrations and then turning it off. Then the electric motor is started, acceleration to the rated speed and bearing heating are checked, and the no-load current of all phases is measured.

The no-load current values ​​measured in individual phases should not differ from each other by more than ±5%. A difference between them of more than 5% indicates a malfunction of the stator or rotor winding, a change in the air gap between the stator and the rotor, or a faulty bearing. The duration of the inspection is usually at least 1 hour. The operation of the electric motor under load is carried out when the technological equipment is turned on.

Post-repair tests of electric motors, in accordance with the current Standards, must include two checks - measurement of insulation resistance and operability of the protection. For electric motors up to 3 kW, the insulation resistance of the stator winding is measured, and for motors over 3 kW additionally. At the same time, for electric motors with voltages up to 660 V in a cold state, the insulation resistance must be at least 1 MOhm, and at a temperature of 60 °C - 0.5 MOhm. Measurements are made with a 1000 V megohmmeter.

Checking the operation of machine protection up to 1000 V with a power system with a grounded neutral is carried out by directly measuring the current of a single-phase short circuit to the frame using special instruments or by measuring the impedance of the phase-zero loop with subsequent determination of the current of a single-phase short circuit. The resulting current is compared with the rated current of the protective device, taking into account the PUE coefficients. It must be greater than the fuse current of the nearest fuse or circuit breaker.

In the process of performing routine repairs, in order to increase the reliability of electric motors of older modifications, it is recommended to carry out modernization measures. The simplest of them is three-fold impregnation of the stator winding with varnish with the addition of an inhibitor. The inhibitor, diffusing into the varnish film and filling it, prevents the penetration of moisture. It is also possible to encapsulate the frontal parts using epoxy resins, but in this case the electric motor may become irreparable.

Security measures.

Before starting work, you should inspect the place of work to be done and put it in order; if it is cluttered with unnecessary items that interfere with work, it is necessary to put it in order and remove all unnecessary things. The electric motor must be de-energized, grounded, and posters posted. Apply portable grounding to the input ends of the electric motor cable. Fence the work area. Work using tools personal protection. Work with verified instruments, mechanisms and proven power tools and accessories. All operations in progress overhaul repairs of electric motor components and parts are carried out in specialized workshops using specialized equipment.

Removal of the fence must be possible only with the use of a tool. When carrying out work in an area protected by a removable fence, it must be completely dismantled.

Sliding or removable guards that allow access for adjustment or installation of controls or sensors on an operating pump must not be obstructed, but must prevent unauthorized access to a potentially hazardous area. Sliding guards attached to the pump must be fixed and in the open position.

The ED must reflect the requirement to prohibit the removal of fences at work pump unit. To diagnose and assess the condition of a particular unit during operation, inspection windows must be provided in the fences, covered with meshes, perforations, and gratings.

Brigade composition.

Electrician for repair of electrical equipment with at least 3 gr. on electrical safety. Electrician repairing electrical equipment with 3 gr. on electrical safety.

Tool.

Files.

Metal brush.

Fitter's knife.

Wrenches 6 - 32 mm.

Screwdriver Set.

Set of heads.

Bench screwdriver.

The brush is flat.

Mount.

Pliers.

Scrub brush.

Wood block

Set of drills

Hacksaw blade

Electric arc welding (OMM5 electrode)

Manual guillotine shears

Manual disc shears

Devices, instruments, mechanisms, protective equipment.

Megger 500 V

Micrometric level

Set of probes

Microohmmeter

Calipers

Safety helmets

Voltage indicator (380V).

Gloves

Latex gloves

Protective glasses

Portable ground electrode

Welding machine

Washing machine for washing components and parts of electrical machines or bath

KHIOT-6 brand paste

Respirator

Machine for cutting the frontal parts of windings SO-3M

Lathe

Gas plasma spraying installation

Device for straightening shaft curvature

Dynamic rotor balancing machine

Soldering iron

Winding machine

Break-in mechanism

Materials and spare parts.

Sealant

Glass tape

Sandpaper

Wiping materials

Keeper tape

White Spirit

Spare bearing kit

Spare ground

Spare fan

Synthetic detergent preparation ML-51

KHIOT-6 brand paste

Set of stoppers

Set of studs

Adhesive varnish

Mica gaskets

Textolite wedges

Concentrated nitric acid

Putty

Chemical resistant enamel

Napkins

10% soda ash solution

Fiberglass

Asbestos cardboard

Cast iron electrode grade B

Table 4.

Sequence of operations.

1.4 Technological map of repair and maintenance asynchronous motor with squirrel-cage rotor

Security measures

The electric motor must be de-energized, the AV switched off, grounding installed, and posters posted. Apply portable grounding to the input ends of the electric motor cable. Fence the work area. Work using PPE. Work with verified devices and tested power tools and accessories.

Brigade composition

An electrician for the repair of electrical equipment with an electrical safety group of at least three. Electrician for repair of electrical equipment with the third electrical safety group.

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Filling technological map repair of the mechanical part of the electric motor

Task: Draw up a technological map for repairing the mechanical part of an electric motor according to the example of Table 1. Draw up a map separately for the repair of cores, housings and bearing shields, and repair of shafts.

1) Study theoretical material on repairing the mechanical part of an electric motor using the textbook, Installation, technical operation and repair of electrical and electromechanical equipment, §§ 9.1; 9.2;.9.3. (provided by the teacher).

Table 1. Technological map for repairing the mechanical part of the electric motor

AC motor

Purpose of work: mastering the ability to fill out route and technological documentation for repairing the mechanical part of an electric motor

Task: Make a table of the sequence of disassembly and assembly of an AC electric motor according to the example of Table 1.

1) Study the theoretical material on disassembling and assembling an AC motor using tutorial, Installation, technical operation and repair of electrical and electromechanical equipment, §§ 8.3., 10.5. (provided by the teacher).

Instruction card for practical work No. 28

Description of the disassembly and assembly sequence

DC motor

Purpose of work: mastering the ability to fill out route and technological documentation for repairing the mechanical part of an electric motor

Task: Make a table of the sequence of disassembly and assembly of a DC electric motor according to the example of table 1.

1) Study theoretical material on disassembling and assembling a DC electric motor using the textbook, Installation, technical operation and repair of electrical and electromechanical equipment, §§ 8.3., 10.5. (provided by the teacher).

2) Fill in the columns of table 1. separately for disassembly and assembly.

Table 1. Sequence of disassembly and assembly of an AC motor

Instruction card for practical work No. 29

Filling out the winding repair process sheet

Purpose of work: mastering the ability to fill out route and technological documentation for repairing the winding of an AC electric motor

Task: Draw up a technological map for repairing the winding of an AC electric motor according to the example of Table 1. Draw up a map separately for the repair of windings made of round and rectangular wires.

1) Study theoretical material on repairing the mechanical part of an electric motor using the textbook, Installation, technical operation and repair of electrical and electromechanical equipment, §§ 10.1.; 10.2 (provided by instructor).

2) Fill out the technological map according to table 1. Each operation should contain no more than one action. If there is more than one option for an operation, describe each option, indicating in the “Operation Description” column in which cases it is performed.

AC electric motor

Instruction card for practical work No. 30

Filling out a flow chart for repairing a DC electric motor

Purpose of work: mastering the ability to fill out route and technological documentation for repairing a DC electric motor

Task: Draw up a technological map for repairing a DC electric motor according to the example of Table 1. Draw up a map separately for the repair of the armature and pole windings.

1) Study theoretical material on repairing a DC electric motor using the textbook, Installation, technical operation and repair of electrical and electromechanical equipment, § 84 (provided by the teacher).

2) Fill out the technological map according to table 1. Each operation should contain no more than one action. If there is more than one option for an operation, describe each option, indicating in the “Operation Description” column in which cases it is performed.

Table 1. Technological map for repairing a DC motor

Instruction card for practical work No. 31

Filling out the technological map for repairing ballasts

Purpose of work: mastering the ability to fill out route and technological documentation for the repair of ballasts and control equipment

Task: Draw up a flow chart for the repair of ballasts according to the model in Table 1.

1) Study theoretical material on the repair of ballasts using the textbook, Installation, technical operation and repair of electrical and electromechanical equipment, § 14.4. (provided by the teacher).

2) Fill out the technological map according to table 1. Each operation should contain no more than one action. If there is more than one option for an operation, describe each option, indicating in the “Operation Description” column in which cases it is performed.

Table 1. Technological map for winding repair

AC electric motor

Scheme of the technological process of repairing asynchronous motors and synchronous generators is shown in Figure 69 and does not require any special explanation.
Since this manual is intended for students of electrification faculties of agricultural universities and future electrical engineers, the manual describes the most important, in the opinion of the authors, issues of repairing electrical machines. In addition, it is necessary to take into account that the State All-Union Order of the Red Banner of Labor Research Institute for the Repair and Operation of Machine and Tractor Fleet (GOSNITI) has developed technological maps and manuals for major repairs asynchronous electric motors, welding and automotive electrical equipment.

Scheme of the technological process for repairing squirrel-cage electric motors.
These documents are compiled in the form of tables that list the numbers and contents of all technological operations, technical conditions and instructions for repairs, and provide information about the equipment, devices and tools necessary for repairs. Technological maps are supplemented with diagrams, sections, and drawings. In repair production, various technical documentation is compiled; it is not the same at different factories and in individual departments, although the contents of individual documents are similar, and some of them are duplicated even at the same factories. Thus, Glavelektroremont METP recommends that its enterprises fill out a defect note and a list of defects after fault detection of machines.
The contents of the note include the vehicle's passport data before repairs and the customer's wishes for changing them. It contains all the dimensions of the stator and rotor cores and winding data of the stator and rotor (winding type, number of slots, wire grade, number of turns in the coil, number of parallel conductors in the turn, number of coils in the group, phase, winding pitch, number of parallel branches, phase conjugation, wire consumption in kilograms, frontal projection, heat resistance class).
The list of defects records all necessary operations throughout the machine, for example, the frame - weld cracks, repair locking surfaces, weld legs, repair fasteners and eye bolts, etc.
Each repaired machine is accompanied by a technological map, which contains information about the customer, the technical characteristics of the machine with its passport data, the value of the phase resistance, the cross-section of the output ends and the insulation class, the size of the stator core and the number of slots, information about the winding data before repair and according to calculation , information about the mechanical part - its condition, information about the control of windings and bench tests.
The technological map is signed by a defect detection technician, a foreman, a calculation engineer and quality control department workers.
The person on duty for drying fills out the drying logs of electrical machines, the contents of which include: customer, order number, passport details of the machine, drying location, information about the start of drying, temperature individual elements machine, the insulation resistance of the stator and rotor windings and the completion of drying. The final results are certified by the person responsible for drying and the site manager.
Separately, the quality control department maintains a book of test reports for each repaired machine. OTK. also draws up an act on the transfer of successfully tested machines to the warehouse finished products. The report indicates the repair number of the machine, type, power, insulation class, voltage, rotation speed, form of execution, price list, cost of repairs, customer. The act is signed by the head of the quality control department and the warehouse manager.
An act of issuance of finished products is drawn up in approximately the same form, indicating the full amount of repair costs. The report is signed by the management of the repair company and the customer’s representative.
Technical documentation for the repair of transformers is more extensive in general and in terms of the content of individual documents. For example, the contents of the defect note include not only the passport data, the data of the HV and LV windings and the dimensions of the magnetic circuit, but also the mass of the oil, the removable part and the total mass of the transformer.
The note is signed by the persons who wound the windings and assembled the transformer, and by the master.
Separately, fill out a transformer oil analysis protocol, which indicates the customer, place, reason and date of sampling, duration of oil operation and the results of physical, chemical and electrical analyzes of the oil. They give an opinion on the quality of the oil. The protocol is signed by the person who carried out the analysis, the site engineer.
For each transformer, a repair (audit) form is filled out, containing the following information: about the customer, the transformer passport, work and measurements performed during the repair process on all components and parts of the transformer (tank, radiator, expander, exhaust pipe, tank and expander fittings, transport accessories, HV, MV and LV bushings, flange cover seals of fittings and bushings, magnetic core and its grounding, HV, MV, LV windings and their press-fit condition, voltage switch, winding insulation details, taps and circuit, oil, additional data), o drying (drying method, its beginning and end, temperature during drying, inspection and crimping after drying, DC resistance of windings in phases of all windings at measurement temperature), preliminary tests (determination of transformation ratios for all windings and taps, insulation resistance, checking the electrical strength of the insulation), about the final tests (data from open-circuit and short-circuit experiments, checking the transformation ratio, resistance of all windings in phases at the measured temperature, group of winding connections, ratios of winding capacitances at different frequencies, etc., insulation test attached voltage, turn insulation test, oil strength). At the same time, data on the devices used in the tests are entered into the form. The form is signed by the person who conducted the tests, the quality control department master, the workshop foreman and the chief engineer.
Transformer drying logs and a protocol for analyzing and testing transformer oil are attached to the form.
Acceptance certificates are drawn up for repaired transformers finished works. During the repair process, they draw up a limit map-report on the consumption of materials, on the basis of which the cost of repairing transformers is determined. Defects of electrical equipment. Fault detection methods
Defect detection is the identification of machine malfunctions during operation or repair. There are two stages - defect detection of the assembled machine and after its disassembly.
Defects of a machine or apparatus are one of the most critical operations, since undetected faults can lead to destruction of the machine in operation, an accident, and an increase in the duration and cost of repeated repairs.
Electrical equipment is characterized by the presence of two parts - electrical and mechanical. If the mechanical part of electrical equipment is defective, check the condition of the fasteners, make sure there are no cracks in one or another part, determine wear and compare with acceptable standards, measure air gaps and check with table values, etc.
All detected deviations from the norms are recorded and entered into a list of defects or a repair card, the forms of which are different at different factories, but the content is almost the same.
Faults in the electrical part of a machine or apparatus are hidden from human eyes, so they are more difficult to detect. Number possible malfunctions in the electrical part it is limited to three:
electrical circuit break;
closure of individual circuits to each other or closure of a circuit(s) to the housing;
closure of part of the winding turns to each other (the so-called interturn or turn-to-turn closure).
These faults can be identified using the following four methods:
test lamp or resistance method (ohmmeter);
current or voltage symmetry method;
millivoltmeter method;
electromagnet method.
Let's consider identifying faults in an assembled machine or apparatus.
A break in a winding without parallel circuits can be determined using a test lamp. If there are two or more parallel branches in the winding, the break is determined with an ohmmeter or ammeter and voltmeter. The obtained value of the winding resistance (for example, the armature winding of a DC machine) is compared with its calculated or certified value, after which a conclusion is made about the integrity of the individual winding branches. Breaks in multiphase machines and devices that do not have parallel branches can be determined by the method of current or voltage symmetry, but this method is more complex than the previous one.
It is somewhat more difficult to determine a break in the rods of squirrel-cage rotors of asynchronous electric motors. In this case, they resort to the method of current symmetry.
The experience for determining breaks in rods is as follows. The electric motor rotor is braked and a voltage reduced by 5...6 times compared to the rated voltage is supplied to the stator. An ammeter is included in each phase of the stator winding. If the stator and rotor windings are in good condition, the readings of all three ammeters are the same and do not depend on the position of the rotor. When the rods in the rotor break, the instrument readings are different, most often
two ammeters show the same currents, and the third one shows a smaller current. When the rotor is slowly rotated by hand, the instrument readings change, the reduced current value will follow the rotation of the rotor and move from one phase to another, then to a third, etc.
This is explained by the fact that when the rotor turns, the damaged rods move from the zone of one phase to the zone of another. A braked asynchronous electric motor is similar to a transformer in short circuit mode. A broken rod is tantamount to transferring the damage zone from short circuit mode to load mode, which leads to a decrease in the current in the stator winding in the part that interacts with the damaged rod.
If several rotor rods break, the readings of all ammeters may be different, but they, as mentioned above, will change cyclically and follow one another (passing through the phases of the stator winding) when the rotor rotates slowly. Various ammeter readings, independent of rotor rotation, indicate damage or defects in the stator winding, but not in the rotor.
The location of the break in the rotor windings of squirrel-cage electric motors is determined using an electromagnet. The rotor mounted on the electromagnet is covered with a sheet of paper on which steel filings are poured. When the electromagnet is turned on, sawdust is located along the entire rods and is absent in the break area.
Breaks in the armature windings of DC machines are determined using an ohmmeter (millivoltmeter).
The closure of individual electrical circuits of electrical equipment, the housing or among themselves, is determined using a test lamp. Megohmmeters are often used in this case. The latter should be given preference, since they can easily determine a short circuit with a relatively high resistance at the point of contact of the circuits with each other or with the housing.
The short circuit between the sections lying in different layers of the armature grooves of the sections to the body is determined using an ohmmeter (millivoltmeter).
The turn circuit in multiphase electric machines and devices is determined by the method of voltage symmetry or special devices, for example type EJI-1.
Thus, turn short circuits in the windings of three-phase electric motors are determined at idle speed using the current symmetry method (the readings of all three ammeters included in each phase of the stator winding, in the absence of turn short circuits, must be the same), and turn short circuits in the stator windings of synchronous generators are determined at idle using the voltage symmetry method (the readings of all three voltmeters connected to the stator winding terminals must be the same).
When determining turn faults in the windings of three-phase transformers, they resort to both the method of current and voltage symmetry.

Rice. 7. Scheme for determining turn short circuits in equipment coils.
Turn short circuits in the windings of single-phase electric machines and transformers are determined with an ohmmeter or ammeter. When determining turn short circuits in the excitation coils of DC machines, it is advisable to use low-voltage alternating current rather than direct current to increase the sensitivity of the test, choosing the appropriate instruments (ammeter and voltmeter).
It should be noted that a turn short circuit in the windings of electrical equipment operating on alternating current is accompanied by a sharp increase in current in the damaged winding, which, in turn, leads to very rapid heating of the winding to unacceptable limits, the winding begins to smoke, chars and burns.
The location of turn short circuits in the stator windings of alternating current electric machines is determined using an electromagnet. The location of turn short circuits in the armature windings of DC machines is determined with an ohmmeter (millivoltmeter).
Usually damaged transformer coils are not defective, but if necessary, the electromagnet method can be used (Fig. 7).
Defects of direct and alternating current machines and transformers during repair are described in detail in the workshop on installation, operation and repair of electrical equipment.

Dismantling of electrical machines. Removing old winding

Disassembling electrical machines into their component parts is not difficult. It is only necessary to mechanize the execution of individual operations as much as possible, using electric or hydraulic impact wrenches, pullers, hoists, etc., and also be careful when removing the rotors of large machines so as not to damage the iron of the stator packages or its winding with the rotor.
The most labor-intensive operation during disassembly is removing the old winding. This is done by the following methods: mechanical, thermomechanical, thermochemical, chemical and electromagnetic.
The essence of the mechanical method is that the body of the electric machine with stator steel packages and windings is installed on a lathe or milling machine and a cutter or
a cutter is used to cut off one of the frontal parts of the winding. Then, using an electric or hydraulic drive, the remaining part of the winding is removed (pulled) from the grooves (with a hook for the remaining frontal part of it). However, when removing the winding in this way, there are insulation residues in the grooves, and additional costs are required to remove them.
2. With the thermomechanical method of removing the old winding, an electric machine with the front part of the winding cut off is placed in a kiln at a temperature of 300...350°C and kept there for several hours. After this, the remaining part of the winding is easily removed. Often the machine is placed in the oven with the entire winding (none of the frontal parts of the winding are cut off), but in this case, after firing, the winding is removed from the grooves only by hand.
It is difficult to create a uniform thermal field in a kiln. Often, the winding insulation ignites in the furnace, leading to a sharp increase in temperature in the furnace, especially in some of its zones. When the temperature rises above the permissible level, machine bodies may warp, this especially applies to aluminum bodies. Therefore, it is not recommended to fire cars with aluminum bodies. Some enterprises study the temperature distribution inside the furnace during its operation and determine the zones in which electrical machines with aluminum housings can be located.
When fired in a furnace, the stator steel sheets are annealed, the specific losses in the steel are noticeably reduced and the efficiency increases; cars. But at the same time, the varnish films between the steel package and the body and between the individual sheets of steel burn out. The latter leads to the fact that after 2...3 firings the tight fit between the bag and the body is broken, the bag begins to rotate in the machine body, and the compression of the bag is weakened. Therefore, firing the insulation of machine windings in molten salts (caustic or alkali) can be considered progressive.
Firing in molten salts is carried out at a temperature of 300°C (573K) with aluminum bodies and 480°C (753K) with cast iron for several minutes. The complete absence of air access to the firing object, as well as the ability to regulate the temperature within the required limits, make it possible to use this firing method for machines with aluminum bodies. Warping of the latter is completely eliminated.
With the thermochemical method of removing the winding, the electric machine, prepared for firing (one of the frontal parts of the winding is cut off), is lowered into a container with a solution of caustic soda or alkali. The machine is in a solution at a temperature of 80...100°C for 8...10 hours, after which its winding can be easily removed from the grooves of the stator packages. With this method, no warping of the housings can occur. This method is especially justified with oil-bitumen insulation of windings.
With the chemical method, an electric machine with a winding is placed in a container with washing liquid of the MZh-70 type. This liquid is volatile and toxic, therefore, when working with it, you must follow safety rules. The technology for removing windings is as follows: loading the container with repaired machines, sealing the container, filling it with liquid, a reaction process that usually takes up non-working time at night, removing liquid, purging the container, freed from liquid, clean air, depressurization and opening of the container, removal of electrical machines and removal of the winding from the stator slots.

5. The electromagnetic method is as follows. A single-phase transformer is made with a removable armature and one removable, or more precisely, replaceable rod. A magnetizing winding is wound onto a non-replaceable rod at mains voltage. One or more motor stators are placed on the second removable rod, the insulation of the windings of which must be burned. The diameter of the replacement rod is selected in such a way as to obtain the smallest (about 5 mm) gap between the stator bore and the rod. The method is convenient in that it allows you to regulate the heating temperature of the stator by changing the voltage supplied to the magnetizing winding or switching the number of its turns. With this method, you can fire cars with both cast iron and aluminum bodies.

According to their design, the windings of electrical machines are divided into three types: concentric, random and template. The latter, in turn, are divided into windings with continuous compounded insulation and sleeve insulation. They are used in large machines with voltages of 3.6 kV and above, so they are not discussed in this book.
In practice, winding repair consists of removing the old one and making a new winding that has the same or improved slot insulation and winding wire data.
Concentric winding is the most outdated, labor-intensive and is used only in electric machines with closed slots. The manufacture of this winding consists of the following main operations: using templates, manufacturing slot insulating sleeves, the material for which is selected depending on the voltage of the machine and its heat resistance class; inserting sleeves into grooves; filling the sleeves with metal or wooden pins according to the size of the insulated winding wire; selection of a winding scheme that produces the lowest voltages between adjacent conductors in the slot of the machine; preparing the wire for winding coils, which consists of removing the insulation at the ends of the wire prepared for winding the coil and waxing it to facilitate pulling through the grooves; winding the smallest-sized coil using two wrappers using special templates to form the frontal parts of the coil; winding the remaining coils, connecting and insulating them.
When making loose windings, insulating groove boxes are first prepared and placed in the grooves. It should be borne in mind that in machines of older series, the groove boxes consist of two layers of electrical cardboard and one layer of varnished fabric. They have been replaced by grooved boxes consisting of film-electrocardboard, and now in small machines of the new series only one thin layer of insulating film is used. Under these conditions, the use of new materials, including winding wires, when repairing electrical machines of old series significantly increases their reliability and, if necessary, can be accompanied by a noticeable increase in the power of the machine. On the contrary, when repairing machines of new series, it is necessary to use only appropriate quality materials and winding wires, otherwise repairing the machine will lead to a decrease in its reliability, deterioration of technical and economic indicators and a sharp decrease in its power. In addition, it is necessary to take into account the narrow specialization and mechanization of work at electrical machine-building plants and the lower level of technology at repair enterprises, which also affects the quality of work, the slot fill factor of the machine and its reliability. The next winding operation is winding onto special, size-adjustable coil templates. This is followed by laying the coils in the grooves, installing wedges, which can also be used in small-power machines of the new series, film, connecting and banding the winding with insulating cords or stockings with the installation of insulating interphase gaskets on the frontal parts of the winding. If it is necessary to connect individual coils, they are insulated with linoxin, polyvinyl chloride or glass lacquer tubes.
Connections between the coils can be made either by soldering (the ends to be connected are tinned, twisted and dipped in a bath of molten solder), or by resistance welding using hand pliers with a graphite electrode.
Drying of the windings of electrical machines, before and after impregnation, is carried out in drying ovens (convective method), by losses in the steel of the stator or rotor (induction method), by losses in the windings (current method) and by infrared irradiation (radiation method).
Typically, electrical repair enterprises have vacuum or atmospheric drying furnaces, the volume of which is determined at the rate of 0.02...0.04 m 3 /kW of the power of the machines for which the furnace is intended. The heater can be electric, including lamp, steam or gas. The heater power is determined at the rate of approximately 5 kW per 1 m 3 of furnace volume. Rational air circulation must be ensured in the oven. Thus, the drying power is greater, the larger number and the power of the drying machines. Drying duration ranges from several hours (6...8) for small machines and up to several tens of hours (70...100) for large machines.
Drying machines inductively requires a magnetizing winding. This method is convenient for drying large machines, which are best dried at installation or repair sites, rather than in a drying oven. This method is more economical than the previous one both in terms of power consumption and drying duration.
Current drying is even more profitable. The drying time is reduced by 5...6 times compared to drying in ovens, and energy consumption is reduced by 4 or more times. The disadvantage of this drying method is the need to have a regulated power source of non-standard voltage. In this case, the winding connection diagrams may be different. The drying temperature and its mode depend on the heat resistance class of the machine and the brand of impregnating varnish. The completion of drying can be judged by the established resistance of the insulation being dried (at a given constant temperature).
The most common method of impregnation is to immerse a winding heated to 60...70°C in varnish at approximately the same temperature. The number of impregnations depends on the purpose of the machine; in agricultural production it is recommended to carry out up to three impregnations. The duration of impregnation is 15...30 minutes for the first and 12...15 minutes for the last.
After vacuum drying For particularly critical machines, pressure impregnation can be used. But to ensure the first and second processes, relatively complex equipment is required.

electromechanical work includes: repair of machine housings, bearing shields, shafts, bearing units, active iron of the stator or rotor, commutators, slip rings, brush devices and short-circuited mechanisms, poles, squirrel cages and output boxes. In addition, these works include banding of rotors and armatures and their balancing.
In the conditions of electrical repair enterprises of the State Committee for Agricultural Equipment, stator and rotor iron, poles and squirrel cages of rotors are usually not repaired. Vehicles with such damage are considered beyond repair, are not accepted for repair and are written off as scrap metal.
Repair of housings and bearing shields, as a rule, consists of eliminating kinks and cracks and is performed by welding.
Currently, almost all electrical machines have rolling bearings, the maintenance and repair of which are much simpler than plain bearings.
Rolling bearings are usually replaced when they wear out. If there are no bearings of the required standard sizes, you can use bearings with other sizes, but the new bearing must have the same load-carrying capacity as the one being replaced. In this case, internal or external auxiliary (repair) bushings are used, the fit (mating) of which is carried out by pressing (with interference), and auxiliary thrust rings are also used under the outer ring of the bearing.
Roller bearings can be replaced with ball bearings in cases where significant axial forces are not observed during machine operation (the run-up of the mechanism shaft does not exceed the run-up of the electric motor).
Ball bearings have a tension fit on the shaft, so before being seated on the shaft they are heated in an oil bath to a temperature of 80...90°C.
Repair of the collector can be carried out with or without disassembly. Repair without disassembly consists of turning (on a lathe or in your own bearings), finishing, grinding and polishing. Refinishing of the collector (using a cutter on a machine, a hacksaw blade or a special scraper) is carried out during each repair of the collector, even if it has not been grooved.
When repairing or replacing the insulation between the collector plates, you should try not to completely disassemble the collector, but use a detachable clamp, which significantly reduces the labor costs for disassembling and especially for assembling the collector. For low-voltage machines, new cuffs can be molded directly when assembling the collector without the use of special molds.
The repaired, fully assembled manifold is heated in a furnace to a temperature of 150...160°C, tested on a machine at mechanical strength at a rotation frequency 1.5 times higher than the nominal one and check for the absence of short circuits between the plates and between the plates and the bushing.
Slip rings are repaired if their thickness in the radial direction reaches 8... 10 mm (less than 50% of the original). The design of the unit with slip rings can be very diverse: split bushing, insulation made of electrical cardboard, flexible micanite and rings; continuous sleeve, split sheet steel sleeve, electrical cardboard insulation and rings; continuous bushing with insulating figured rings, between which the machine rings are located; continuous sleeve, micafolia or micanite insulation and rings. All designs of slip ring assemblies, except the last one, are assembled with an interference fit in a cold state.
The slip rings are checked for the absence of short circuits between them and the housing and for runout (radial runout should not be more than 0.1 mm at a rotation speed of up to 1000 rpm and 0.05 mm at a higher speed, and axial runout should not exceed 3.., 5% of ring thickness).
Repair of brush devices (traverse with fingers, brush holders with springs and clips and brushes) most often consists of restoring the insulation of the brush holder fingers, reliable contact between the harnesses and the brush, adjusting the brush holder springs and installing, adjusting and running in the brushes. The brush holders are insulated with getinax end washers and baked paper on the pin neck, thick according to the repair flow chart.
The choice of brushes depends on the purpose of the machine and the characteristics of its operation. It is recommended to install electrographite brushes (EG) in AC machine exciters, allowing a current density of 9...12 A/cm 2 and a linear rotation speed of 40...45 m/s; in crane motors - carbon-graphite (T and UG) with parameters of 6 A/cm 2 and 10 m/s and electrographite; in low-voltage generators (up to 20 V) - electrographite and copper-graphite (M and MG) with parameters 14...20 A/cm 2 and 15...25 m/s; in automobile electric machines - copper-graphite; in machines with slip rings - graphite (G), electrographite and copper-graphite.
Brushing pressure is recommended between 1500 and 2000 Pa.
Repair of the short-circuiting mechanism consists of restoring the worn side ribs of the short-circuiting ring, fork pins and spring contacts by welding and surfacing or replacing the worn part with a new one.
To bandage the stator windings of machines of relatively low power, stockings or keeper tape are used. The frontal parts of the windings of various coils and phases are fastened with a bandage into a single unit, which after impregnation and drying becomes monolithic. This provides the necessary mechanical strength of the winding during starts and sudden overloads of the machine. In large machines, so-called bandage rings are used; they are placed on top of the outer frontal parts of the machine coils. Each reel is tied to a ring with keeper tape.
A special role is played by banding the windings of rotors and armatures of machines, which experience not only electrodynamic loads during machine operation, but also centrifugal forces. Rotors and armatures are banded on lathes or special banding machines equipped with devices for tensioning tinned steel banding wire.
A layer of insulation made of micanite and electrical cardboard is laid between the winding and the wire. With a wire diameter of 0.6 to 2 mm, the wire tension should be from 200 to 2000 N, the number of turns of the bandage is calculated on centrifugal forces, which should not exceed 400 N per 1 mm 2 wire section. The bandages are soldered along the entire circumference to turn them into a continuous ring.

In repair practice, parts from various materials restored using manual electric arc and gas surfacing and welding, automatic surfacing and submerged arc welding, vibratory arc surfacing in a jet of coolant, welding and surfacing in a shielding gas environment, electric spark processing and build-up both in air and in a liquid environment, metallization, cooling, chemical nickel plating.
When repairing electric motors, a relatively large volume consists of work on increasing the seating surfaces. For these purposes, vibrating arc surfacing with flux-cored wire and surfacing in a carbon dioxide environment are widely used. The first is used to restore shafts, axles and axles with a diameter of more than 30 mm. In this case, the hardness of the surfacing layer is 1.5...2 times higher compared to the hardness of the layer obtained by vibrating arc surfacing in a liquid. This improves the quality of the surfacing layer.
After surfacing, a groove is made and the surface is polished, and if necessary, grooves (spline grooves) are milled.
For finishing the surfaces of shafts instead of grinding, strengthening the surface layer to a depth of 0.2...0.3 mm, increasing the wear resistance and fatigue strength of the part, an electromechanical processing method is used, which consists in the fact that when processing a part on a lathe, the part and the cutter a voltage of 2...6 V is supplied and a current of 350... 1500 A flows at the point of their contact.
Cast iron frames and bearing shields are welded using gas welding. Before surfacing, the parts are heated in a furnace to a temperature of 300...400°C, while cast iron electrodes are used, and borax or other mixtures are used as flux.
After surfacing, the parts are fired at the same temperature for 4...6 hours, after which they are slowly cooled in a switched off furnace (12...14 hours). IN Lately At repair enterprises of the Goskomselkhoztekhnika system, galvanic electrical rubbing installations are used to restore bearing seats in parts housings.
Restoration can be carried out on holes with a diameter of 50 to 150 mm. The operating principle of the installations is based on the electrolysis process, accompanied by the deposition of metal on one of the electrodes. The part to be restored is connected to the negative pole of a power source with a voltage of 24 to 30 V, for example, a PSO-300 converter. An electrode wrapped in a material capable of absorbing (absorbing) electrolyte is inserted into the hole to be restored. The electrolyte is supplied to the absorbent material using a pump with a flow rate of 20 l/min. When rotating the electrode with a frequency from 20 to 40 rpm (using any vertical drilling machine) an electrolyte bath is created in the absorbent material, in which the electrolysis process occurs. A set of electrodes consists of steel parts wrapped in absorbent material, which can be cotton fabric, for example, keeper tape with a layer of up to 2.5...3 mm. The gap between the absorbent layer and the surface of the growing hole is 1.5...2 mm.
To build up parts made of steel and cast iron, an electrolyte of the following composition is used: zinc sulfate - 600...700 g per liter of warm water and boric acid- 20...40 g per liter of warm water. The acidity (concentration) of the electrolyte is pH = 3...4, it is checked monthly, and the electrolyte is completely replaced once a month.
For aluminum parts A solution of 150 g of aluminum sulfate in a liter of water is used as an electrolyte. Electrolyte acidity pH=3...3.5.
The current density during etching, which precedes build-up, is 1... 1.5 A/cm 2 (etching duration 8... 10 s) and during build-up 2...3 A/cm 2. The growth rate is 20...30 µm/min.
Preparing the bearing shield for restoration involves cleaning it with fine sandpaper, degreasing it with a rag soaked in gasoline or acetone, and drying it. With the described extension method, it is necessary to isolate the drilling machine table in order to use the body and table as clamps of different polarities. For safety reasons, the electric motor is isolated from the machine body. The worker servicing the installation wears glasses, a rubber apron and rubber gloves. The floor of the machine is lined with rubber mats. Installation and removal of parts is permitted only when the voltage is turned off.
Recently, elastomers have been used to restore bearing seats, in particular GEN-150 (B). To dissolve 20 parts by weight of elastomer, 100 parts by weight of acetone are required. The part to be restored is cleaned of dirt and corrosion, degreased, cleaned with acetone and dried. The elastomer is applied to the part through a tube.