Inspection of magnetic starters after repair, measurement of gaps. Repair of electromagnetic contactors. Functional testing and maintenance

To switch electrical devices of low-voltage equipment, devices called magnetic starters or contactors are used.

With the help of such devices the following is carried out:

• Turning on or off electric motors of mechanical drives in industrial equipment;
• Outdoor lighting system control settlements and illumination of historical and industrial sites;
• When using electric heating, heating elements of heating devices are connected and disconnected;
• With their help, they switch electric motors and other starting elements in automation circuits;
• Switching devices are also widely used in household equipment.

Such devices are available for single-phase or three-phase starters.

Device selection

As a rule, the choice of a magnetic starter is made at the equipment design stage. Sometimes the question arises of how to choose a magnetic starter during the repair process.

To do this, follow the following rules:

• First of all, technical characteristics and design features are considered;
• Select the device for the appropriate supply circuit voltage. In most cases this voltage is 220/380 volts. Less commonly, the switched network has a voltage of 380/660 volts;
• When choosing a device, consider the rated operating current of the switched mechanism. They are available for various switching currents from 6.3A to 250A;
• Then pay attention to the mechanical wear resistance parameter. It shows how many operation cycles the device can withstand without repair;
• The number of switching poles is taken into account;
• What voltage are the coils designed for? magnetic starters. They are available for supply voltages from 9 to 380 volts;
• Often contactors have auxiliary or additional contacts. They are used in automation and signaling circuits;
• The industry has mastered the production special devices, which can perform reverse switching of engines. Such devices have two contactors in one housing;
• When choosing a magnetic starter, pay attention to the presence of a thermal protection relay.

At self-connection equipment, the choice of starter is made according to the engine power.

Based on the obtained value, the motor is selected in such a way that the rated operating current of the three-phase motor is less than the current of the magnetic starter.

That is, the calculated data must be less than the values ​​of the selected contactor. By default, the calculation assumes that the contactor is capable of withstanding inrush currents, which are many times higher than the operating currents.

So, to connect a 3.7 kW motor, the operating current will be 3.7 * 2 = 7.4 A. To connect asynchronous motor such power, it is enough to choose a magnetic starter with an operating current of 10 A.

There are mathematical formulas for accurate selection of a device. Which allow you to accurately calculate the contactor parameters.

Inom.=P/(U*η* cosφ*√3),

This formula is valid for selecting a device for 3-phase voltage. The coefficients η take the value 0.87, and cosφ= 0.88.

Calculate starting current according to the formula:

Istart = k*Inom., where k is the current multiplicity factor. It has a value of 7-8, depending on engine power.

To make the final choice, it is necessary to calculate the shock current short circuit at the moment of launch. It is determined by the formula:

i= (1.2-1.4)*Iп*√2,

After the calculations have been carried out, it is necessary to select a magnetic starter from model range, we select both for the engine and for other equipment. After selecting a magnetic starter based on current in the model range table, the starter is mounted on a DIN rail and the circuit is assembled.

Symptoms of device malfunction

Like all mechanisms, equipment failure occurs during operation. Malfunctions are characterized by the following symptoms:

• When turned on, you can hear a strong buzz from the starter. Which can lead to failure of the contactor coil. A normally operating device emits a barely audible hum;
• The main contacts are not switched on evenly. And as a result, the contacts burn out, and if a phase is lost, the electric motor may also fail;
• Reversible devices do not have reverse;
• The anchor sticks to the core;
• There is no self-locking.

Device repair

In order to repair a magnetic starter, it is necessary not only to know the symptoms, but also the repair methods. If the contacts are switched on unevenly, tighten the contact clamp.

If necessary, clean the contacts from oxides and adhering metal. If there is a strong hum, the magnetic starters are adjusted. Tighten the screws securing the armature and core. Check the condition of the short-circuited turn.

Its damage is characterized by ringing and rattling of the magnetic starter when it operates. Check the fit of both halves of the core. In case of incomplete fit (less than 70%), the magnetic starter is repaired to restore the contact surface.

To do this, press carbon paper between the cores. If the surface is insufficient, grind the cores. Thus, the humming of the magnetic starter is eliminated, and the presence of a gap explains why the contactor is humming.

The reverse is restored by adjusting the mechanical rods. The reason for armature and core sticking may be insufficient or missing dielectric gasket.

Check the thickness or presence of the gasket, as well as the air gap.

If there is no self-locking, adjust the block contacts. When this cannot be done, the contacts are changed.

In order to make sure that the device is working properly, you need to know how to check the functionality of the magnetic starter.

Functional testing and maintenance

To do this, it is necessary to carry out an external inspection of the device. Pay attention to the condition of the coil. It should not have visible darkening or damage.

The contact group should not have any distortions, and the contacts should close simultaneously.
Measure the activation and shutdown voltage of the device. The device should operate when the voltage gradually rises from 0 to 0.85 Unom. And turn off when the voltage drops to 0.45 Unom.

In order for the switching device to operate for a long time, it is necessary to carry out maintenance of the device during operation.

To do this, check the status of the connections. Clean the device from dust. Monitor the state of switching contacts. Inspect the metal parts of the device.

Pay special attention to the condition of the spring. It should be pretty tough. The turns are distributed evenly along the entire length. The anchor should not jam or warp.

If there are mechanical faults, lubricate or grind the parts. If the device is equipped with a thermal relay, its performance is checked on a special stand under laboratory conditions.

This test cannot be done at home. If a malfunction is detected, the device is repaired or replaced with a working one.

Contactors- these are switching electromagnetic devices designed for remote switching on and off of power electrical circuits under normal operating conditions. They are widely used in electrical installations of industrial enterprises and are the main power devices of modern automated electric drives. In three-phase electrical installations AC three-pole contactors are used, which consist of electromagnetic, contact and arc extinguishing systems (Fig. 3, o - c).
The electromagnetic system serves to remote control(on and off) contactor and consists of a yoke with a core, an armature, a short-circuited coil, an electromagnet coil and parts for attaching the electromagnet to the insulating panel. The core and armature are made of sheets of electrical steel 0.55 mm thick (the outer sheets are 0.8 mm thick).
The contact system consists of main moving and fixed contacts, flexible connections and auxiliary contacts that serve for switching in the contactor control, blocking and signaling circuits. The main contacts are provided with an arc extinguishing system, which is a chamber with arc extinguishing steel plates coated with a layer of copper. The chamber is made of fire-resistant material and consists of two halves. The plates inside the chamber are located perpendicular to the barrel of the electric arc, which (when the contactor is turned off) is drawn into the grid, divided into a number of small blowouts, cooled and extinguished.
A three-pole contactor has three pairs of main contacts, provided by three (one for each pole) arc extinguishing devices.
The contactor is controlled as follows. When voltage is applied to the circuit of the electromagnet coil, its core attracts the armature, which rotates at a certain angle and presses the movable contacts, located on the same shaft with the stationary armature, to the stationary ones. When the electrical circuit of the coil is broken, its rod ceases to hold the armature and the moving contacts fall away, breaking the electrical power circuit.

Rice. 3.: a - general view; b - electromagnetic system; e - contact and arc extinguishing systems; 1 - insulating panel; 2 - arc extinguishing chamber; 3 - emphasis; 4 - electromagnet; 5 - bearing; 6 - shaft; 7 - shaft insulation; 8 - fastening contact system on the shaft; 9 - block contacts; 10 - bearing; 11 - yoke with core; 12 - electromagnet coil; 13 - anchor holder; 14 - anchor; 15 - short-circuited turn; 26 - plates of the arc-extinguishing chamber grid; 17 - fixed main contact; 18 - movable main contact; 19 - contact spring; 20 - movable contact holder; 21 - flexible connection

The armature can also be held in the on state by a latch. Such contactors have additional electromagnetic device, which disconnects the contactor by releasing its moving part from under the latch.
When executing current repairs contactors at their installation site, first disconnect all wires, cables and buses ( major renovation usually produced in electrical repair shops). The repair process mainly involves replacing damaged or worn parts with new ones and then adjusting and testing the contactors. Basically, it is necessary to change the main contacts, flexible connections, arc chutes, electromagnet coils, springs and short-circuited turns.
The arc chutes are removed from the main contacts, the screws that secure the flexible connections to the moving contacts are unscrewed, and the moving contacts are removed. Then remove the fixed contacts and wash them. In some cases, the contact surfaces of all disassembled joints are cleaned and lubricated with a thin layer of technical petroleum jelly. Next, the contacts are installed in place in the reverse order of disassembly.
Damaged flexible copper plates are replaced with new ones. In cases where there are more than 20% of such plates, it is recommended to completely replace the flexible connections with new ones. Cameras with severely damaged external or internal parts are also replaced with new ones.
The faulty electromagnet coil is replaced with a new one or its winding is rewound, maintaining the diameter of the wire and the number of turns. When winding a coil with a thin wire, a flexible wire with a diameter of 0.8 mm or more is used for the terminals. In this case, the leads are connected to the coil wire with POS 30 solder, and then the soldering points are insulated with a micanite strip 0.3 mm thick and 8-10 mm wide. The coil leads are secured to the frame with threads, copper tips are soldered to the ends, and the finished coil is wrapped with cotton tape. Finally, the coil is checked by test (at least 10 cycles) by turning the contactor on and off.
A broken short-circuited turn is replaced with a new one: first, the steel plates attached to the outer sheets of the core package are bent, the damaged turn is removed from the groove in the core, and then a new turn is installed in the groove and secured by bending the steel plates.
Damaged springs are replaced with new ones from the spare ones supplied with the contactor.
If the insulation of the movable contact shaft is damaged, it is replaced with a new one made from a material equivalent to the one being replaced in its properties and thickness.

At the end of the main operations, the initial and final pressures of the main contacts are measured using a dynamometer.
At the final stage of contactor repair, they check whether the circuit is assembled correctly, whether the movable contacts are firmly attached to the shaft, and whether the armature is in good contact with the core. Then post-repair tests are carried out: the insulation resistance, the ohmic resistance of the electromagnet coil winding are measured and the accuracy of the contactor operation is determined when the voltage drops.
The insulation is tested with a 500 V megohmmeter, checking its resistance between the current-carrying parts of the contactor and other non-live parts. The insulation resistance should be no more than 0.5 MOhm. The ohmic resistance of the electromagnet coil winding, measured at 20° C, should not differ from the passport data by more than 10%. A contactor installed vertically must be switched on when undervoltage, amounting to 85% of the nominal.
Significant heating of the contacts and electromagnet coil, as well as strong humming of the electromagnetic system, indicate unsatisfactory quality of repairs and poor-quality adjustment of individual parts and systems of the contactor (mainly electromagnetic and contact).
Repair of magnetic starters
The magnetic starter consists of a contactor and thermal relays. It performs control and protection functions, such as starting, stopping and reversing the electric motor, turning it off in case of overload and voltage failure (zero protection).
Magnetic starters mainly use PA and PS contactors. The PA contactor (Fig. 4) of the magnetic starter is a single-block design with conductive parts isolated from the device body. It consists of a magnetic system (coil 3, armature 4, core 20), a contact system (auxiliary contacts 6, fixed contacts 16, bridge 15 with moving contacts), a mechanism with a return spring 12, a lever 10 and a traverse 11.
Currently, magnetic starters of the PMA series are also used (mainly for remote control and protection of three-phase squirrel-cage motors with a power of up to 75 kW) and PML, allowing up to 1200 starts per hour, with built-in thermal relays (RTT and RTL, respectively).

Rice. :
a - general view; b - side section; 1 - base; 2 - anchor stop; 3 - coil; 4 - anchor; 5 - arc extinguishing chamber; 6 - auxiliary contacts; 7 - shaft (axis) of the lever; 8 - bushing; 9 - stand; 10 - lever; 11 - traverse; 12, 14 - return and contact springs; 13 - liner; 15 - contact bridge; 16 - fixed contact; 17 - bracket; 18, 19 - spring and core latch; 20 - core

Thermal relays RTT, RTL, TRP, TRN, used in magnetic starters, serve to protect electrical circuits from overload currents. A thermal relay, for example TRL (Fig. 5), works as follows. The operating current passes through heater 2 (replaceable high resistivity alloy plates). Nearby there is a bimetallic plate 1, the lower end of which is fixed and the upper end is free. The movable contacts 7 of the thermal relay are fixed to a plastic stand 6, which rests against a spring. This spring tries to open the contacts, but with the help of lever 4, which rests against the protrusion on the relay body, the contacts are kept in the closed state. In the case when the current passing through the heater is small (a small amount of heat is released, the bimetallic plate almost does not bend, the moving parts of the relay occupy the position shown in the figure), the relay contacts are closed. If the current through the heater exceeds the nominal value (overload mode), the amount of heat generated in the heater increases, the bimetallic plate bends (in the direction of the arrow) and turns the curly bracket 5, which acts on the lever 4 of the contact stand. As a result, the relay contacts open under the action of the spring. After the bimetallic strip has cooled, the moving parts cannot independently take their original position, so it is necessary to press the upper part of the 3rd contact stand.
When repairing contacts and the extinguishing device of a magnetic starter, basically the same operations are performed as when repairing contactors. In thermal relays, heating elements are most often damaged (burn out), which are replaced with new ones.
The contacts of magnetic starters are coated with metal-ceramic surfacing, which increases their service life. When the surfacing wears out, the contacts should be replaced with equivalent ones (factory-made).
The magnetic starter is checked and tested according to the program and standards of the manufacturer. Test results should not differ from the passport data by more than 10%.

Rice. 5.

Magnetic starters are designed for remote starting and stopping of electric motors, reverse control and other manipulations. The task also includes protecting equipment from overloads if there is a protection circuit. If the connected load is correctly calculated, starters can operate for months and even years without any intervention, cost or investment. But like any electrical equipment, they have malfunctions and breakdowns, which means that the list of work with this equipment includes maintenance and repair.

All these works are carried out at different times. This depends on many factors, the main one being the intensity of the magnetic starter. For example, emery in a workshop: if short-term but frequent starts are made, the closing and opening of the main contacts occurs more often, and the electric arc leaves marks on the main contacts. More power of the connected electric motor means more powerful arc.

As a result, the contact heel burns. This, in turn, breaks their tight fit and heating begins, which will increase over time. And the result can be disastrous if for some reason the protection does not work. Both the coils and the engines are burning. This can be avoided by carrying out maintenance.

First, you need to turn off the electric motor and hang up a sign “Do not turn on! People are working!”, and then take the necessary measures to prevent erroneous or accidental activation of the service work area (according to the rules).

You can pull out the inserts (fuses) in the distribution cabinet. It is necessary to do this, since one poster is not enough - there are cases when the poster is in its place, but they do not notice it and try to turn on the equipment. Then you need to remove the starter cover, sweep away the dust with a brush and immediately remove it with a vacuum cleaner. For these purposes I use an old “Rocket”. You can do this in two ways: “suck” or “blow”, the result will be equally positive.

Next you need to get to the main contacts; this is done in different ways depending on the design of the model. It is necessary to remove the main contacts and thoroughly clean and polish them with blued material (do not use a needle file or abrasive materials). While inside the starter, it is necessary to measure the insulation resistance between the entire electrical part and the housing, which must be at least 10 MOhm. After completing these steps, you can put everything back in place, check the tightness of all bolts and screws, sweep away any remaining dust and close the lid.

Repair of a magnetic starter is carried out in case of replacement of the coil, block contacts, thermal relay, main contacts or other part of the device.

As a rule, the contacts of thermal relays and block contacts do not require frequent maintenance, since they are located in the control circuit, where the currents are small.

During repairs, if possible, it is advisable to check and test the thermal relay at the stand.

All this work takes a little time, and if it is done on time, then the magnetic starters on your site will serve you faithfully for a long time. Magnetic starters are quite unpretentious equipment. A little advice: use Grover washers on all screw connections; this is an extremely necessary element in electrical connections. You need to finish working with the starter by washing the housing.

Magnetic starters, as the name suggests, were conceived as a switching device for starting electric motors. Therefore, the number of power poles for these devices is almost always equal to three - according to the number of phases of the network. Starters are often equipped with thermal overload relays and a housing with start and stop buttons.

But the starter turned out to be a very convenient and functional thing. A wide range of rated currents, small dimensions and the possibility of autonomous installation outside any switchgear or panel have led to the fact that magnetic starters began to be widely used in everyday life for connecting various powerful electrical receivers, for example, heating boilers, to the network.

Like any other electrical device, a magnetic starter also periodically needs repair and maintenance.

How does a magnetic starter work?

In general, this is, at a minimum, a coil of thin wire in varnish insulation, housed in the same plastic housing with contacts. Contacts, as usual, are divided into movable, mechanically connected to the spring-loaded core of the coil, and fixed, permanently located in the upper part of the housing.

At the same time, for starters designed for a current of 20 amperes or more, one can clearly distinguish between three pairs of power pairs of contacts, and pairs of contacts of auxiliary control circuits, designed for low currents. The number of low-current contacts is practically unlimited, especially since for many starters it is possible to purchase additional contact attachments that allow you to assemble very complex circuits on starters.

This design provides the starter with a not particularly high degree of protection from external influences - at the IP00-IP30 level. If it is necessary to achieve a greater degree of protection, you will have to use starters in an additional protective casing, often equipped with their own buttons for starting, stopping and returning the thermal relay, if any.

Rice. 1. PML magnetic starter device:

1 - base made of heat-resistant plastic, 2 - fixed part of the magnetic circuit, 3 - moving part of the magnetic circuit, 4 - electromagnetic coil controls, 5 - contact clamps, 6 - metal platform (for starters rated over 25 A) 7 - crossbar with movable contacts, 8 - mounting screw, 9 - return spring, 10 - aluminum rings, 11 - fixed contact, 12 - clip with a notch for fixing the conductors.

The maintenance program for magnetic starters is simple and includes the following items:

1. External inspection for damage and chips of the housing, as well as removing contaminants (not only from the surface of the housing, but also from the surface of the electromagnet core). Chips and damage to the housing occur not only due to shocks and falls, but also due to prolonged exposure to vibrations caused by the operation of a worn-out AC network and faulty installation of the starter, as well as its own defects.

If damage to the housing has led to the fact that the starter cannot be securely fastened, or its contacts cannot open/close freely, then there is simply no other option than replacing the housing or starter.

Special attention should be paid to checking the presence of all parts and components of the starter. For example, a movable contact plate along with its preload spring can easily be “lost” - a new one will be required.

Introduction

Further mechanization and automation of processes in livestock farming, poultry farming and plant growing, the supply of new, more complex high-performance machines and units, requires electrical installers not only to reduce commissioning time, but also to provide high quality work, ensuring high reliability, durability and safety in servicing electrical installations.

In the conditions of intense work of enterprises, repair of electrical equipment must be carried out in an extremely short time, which is possible with high level organization of repair work. Since the needs of enterprises for transformers, electrical machines and devices are not yet fully satisfied, timely and high-quality repairs of this electrical equipment have become one of the main factors ensuring normal work enterprises.

During the repair process, it is possible to modernize electrical equipment, change its technical characteristics in the right direction, and increase operating efficiency. Long-term practice of electrical repair shops of enterprises and electrical repair plants has shown that over 70% of damaged electrical equipment received for repair are transformers, electrical machines and switching devices, in the repair of which electrical plumbing plays a significant role.

In my work, I examined the issues of maintenance and repair of magnetic starters

1. Technical description

1.1 Purpose

Electromagnetic starters are intended for use in stationary installations for remote starting by direct connection to the network, stopping and reversing three-phase asynchronous electric motors with squirrel-cage rotor AC voltage 660 V frequencies 50 and 60 Hz. In the presence of three-pole thermal relays of the RTT and RTL series, the starters protect controlled electric motors from overloads of unacceptable duration and from currents arising when one of the phases is broken. The starters are suitable for operation in control systems using microprocessor technology when the switching coil is bypassed with an interference suppression device or when thyristor control.

Designed for remote start by direct connection to the network and shutdown of three-phase asynchronous electric motors with a squirrel-cage rotor. Additional functions: reversing, in the presence of thermal relays - protecting motors from overloads of unacceptable duration, including those arising when one of the phases fails, changing the circuit diagram for switching on the Y/A windings.

1.2 Specifications

The most common starters are the PME and PAE series. They are used to control electric motors with power up to 75 kW. The designations of the starters are deciphered: PME - series, the first digit after the series is the value (0 - zero, 1 - first, 2 - second), the second digit - version (1 - open, 2 - protected, 3 - dust-proof, 43 - with four closing block contacts, 5 – protected, 43+2Р – with four normally open and 2 normally closed block contacts, b – dust and waterproof, 7 – open). The third number is the possibility of reversing and the presence of thermal protection (1 – non-reversible and without a thermal relay, 2 – non-reversible with a thermal relay, 3 – reversible without a thermal relay, 4 – reversible with a thermal relay).

Table 1 – Technical data of magnetic starters of the PME series

Table 2 - Dimensions

Figure 1 shows the PME series magnetic starter, overall dimensions which are shown in Table 2.

1.3 Design and principle of operation

Magnetic starters provide protection for electric motors against voltage drop (zero protection) and overload. When the voltage drops to 35–40% of the nominal value, the retractor coil ceases to hold the electromagnet armature and the starter contacts open. Overload protection is carried out using thermal relays TRN, TRP, RTT, RTL.

Figure 1 – PME series magnetic starter

The diagram of the device and operating principle of the relay is shown in Figure 2. The relay consists of a heating element 1, connected in series to one of the phases of the electric motor circuit, a bimetallic plate 2 holding the trigger 3, normally closed contacts 4, which are connected in series to the starter coil circuit. As the current increases due to motor overload, the temperature of the heating element increases.

Figure 2 – Diagram of the thermal relay device:

1 – heating element; 2 – bimetallic plate; 3 – latch (trigger mechanism); 4 – normally closed contacts; 5 – return button; 6 – spring

Figure 3 – TRN thermal relay:

Figure 4 – TRN thermal relay:

1 – heating element; 2 – return button; 3 – thermal relay contacts; 4 – bimetallic plate; 5 – adjustment lever scale; 6 – lever-regulator

Under the influence of heat, the bimetallic plate is deformed and releases the latch of the trigger mechanism, which leads to the opening of the relay contacts and breaking the starter coil circuit. Charging the trigger mechanism after the relay is activated and returning its contacts to the closed position is carried out after the bimetallic plate has cooled by pressing the reset button 5 of the relay, the head of which comes out from the hole in the cover of the starter box. Relay heating elements are available in various rated currents and are selected according to the rated currents of the motors. The TRN relay is two-pole, TRP is single-pole, RTT, RTL are three-pole, they are built into magnetic starters PMA, PML. TRP relays are equipped with PAE magnetic starters of size four and above. TRN relays are built into magnetic starters PME, P6 and PAE of the third size (Figures 3, 4).

AC and AC contactors DC designed for remote and automatic control electric motors.

The P6 series contactor is used for frequent switching on of low-power electric motors (Figure 5). It consists of plastic case, the two halves of which are connected by four screws.

Figure 5 – Contactor P6:

1 – spring; 2 – contact bridges; 3 – contact plates; 4 – traverse; 5 – movable part of the core; 6 – winding; 7 – core; 8 – blocking contacts

The electromagnetic system includes a stationary part of the core 7 and a winding 6, a movable part of the core 5 connected to a plastic crossbeam 4, on which contact bridges 2 with movable contacts are mounted. The pressing force of the contacts is provided by springs 1. Fixed contacts are soldered to contact plates 3. There are locking contacts 8. To control the contactor, a two-button station with “Start” and “Stop” buttons is used.

2. Organization of operation and repair of equipment

2.1 Maintenance

During the period between repairs, maintenance of electrical devices is carried out, which is a set of operations or an operation to maintain the functionality or serviceability of the device during intended use, standby, storage and transportation. The device is not disassembled.

The typical scope of maintenance work for magnetic starters includes: cleaning of dust and dirt, lubricating rubbing parts, eliminating visible damage, tightening fasteners, cleaning contacts from dirt and deposits, checking the serviceability of casings, shells, housings, checking the operation of signaling and grounding devices .

It is recommended to check and adjust thermal relays in the laboratory using special electrical devices. Checking the relay begins with an external inspection: checking the presence of seals, the integrity of the casing and its tight fit to the base, the condition of the seals, and cleaning the relay.

After removing the casing, they begin an internal inspection: clean the parts, check the tightness of screws, nuts, fastening springs, contacts, bearings, magnetic circuits; check the reliability of internal connections; regulate mechanical part relay; The contacts are thoroughly cleaned and polished with blued material (needles or abrasive materials should not be used).

Next, measure the insulation resistance with a 1000 V megohmmeter between the electrical parts of the relay and the housing, which must be at least 10 MOhm, and check the settings. If defects are found that are beyond the ability to eliminate them in the laboratory, the relay is replaced with a new one.

2.2 Repair work

As a result of operation, accidents, overloads and natural wear and tear, some electrical equipment and networks fail and must be repaired.

Repair is a set of operations to restore the serviceability or performance of electrical devices, restore their resources or their components. A repair operation is understood as a completed part of a repair performed at one workplace by performers of a certain specialty, for example: cleaning, disassembling, welding, making windings, etc.