Abstract technology of repair and maintenance of an asynchronous motor with a squirrel-cage rotor. Technological map of disassembly and assembly of the engine Typical flow sheets repair of electric motors 6kv

Dismantling is the dismemberment of an electrical machine into separate parts and assemblies. The most important task is to carry it out in such a way as to prevent additional damage to the machines and their components.

To do this, before disassembly, in particular, in case of severe corrosion of fasteners, all bolts, nuts and joints are lubricated with transformer or machine oil. Sometimes it is advisable to apply rags moistened with oils or kerosene, other organic solvents to them. The exposure time of the solvent is determined by experience; if the gank or screw is not turned, it is prolonged.

Figure 6. Disassembly sequence induction motor type 4A (power up to 10 kW)

The order of disassembly, the tools and tools used depend on the type of machine, its power and design features. For an asynchronous motor of the 4A series with a power of up to 10 kW with a squirrel-cage rotor, a closed, ventilated version, the disassembly procedure is as follows:

The fan cover 2 is removed (Fig. 6. a) To do this, the screws fastening it to the machine body are unscrewed

Fan 1 is removed, while the spring ring is removed from the shaft groove. For removal, there are often special threaded holes in the steel fan sleeve

Fasteners are removed, bearing caps are removed 3.

The rear bearing shield 5 is removed (Fig. 6, b). located on the side of the removed fan.

To remove (after removing the shield fastening bolts), with light hammer blows made of soft material (wood, aluminum, etc.) along the edge of the part, move the shield away from the housing along the shaft. In this case, the rotor shaft is held by hand or with a device on weight to prevent it from falling onto the stator, otherwise the sheets of steel of the magnetic circuit can be damaged. You can use a regular hammer. but in this case it is necessary to use soft pads. Often, when performing such work, special devices are used. such as a universal screw extractor (fig. 7) or a hydraulic mobile extractor, etc.

1- emphasis; 2 - screw; 3 - capture; 4 - handle

Figure 7- Universal screw extractor.

The front shield 4 is removed (located on the drive side), and the fastening bolts are also preliminarily removed (Fig. 7. c). Usually it is separated together with rotor 6. However, often the last one, after removing the bearing shields, remains in the stator bore, then a special operation is performed to remove the rotor (Fig. 7, c). By weight, the rotors are divided into micro (0.01-0.1 kg), small (0.1-3 kg), medium (3-1000 kg).

When removing the rotor, care must be taken not to damage the frontal parts of the winding, the fan wings (on the squirrel cage), the magnetic circuit and other parts. The withdrawal of the rotor from the stator is one of the most critical operations, the slightest negligence leads to serious damage (violations of the insulation of current-carrying parts, damage to the magnetic circuit, etc.) Small rotors are removed manually by placing an electric cardboard in the air gap, or using wooden supports under the shaft. Medium and large - with the help of devices various designs(depending on the design and mass of the rotor), for example, as in fig. eight.

Figure 8 - Pulling out the rotor with

It is permissible to remove the rotor when removing the front shield. But once again we emphasize that you should carefully monitor to prevent damage to other parts of the machine during this operation.

Usually, ball bearings (8) remain on the rotor shaft and are removed from it by pullers only in cases of their replacement or repair of rotor parts (Fig. 7, d).

For asynchronous electric motors with a phase rotor, when removing the rear shield (located on the side of the slip rings), first remove the casing, then remove the brushes and, finally, unscrew the fixing bolts, remove the body of the rings. At the same time, the connecting clamps are soldered from the output ends. Removal and disassembly of slip rings is performed only in case of their repair in the same way as collectors of DC machines.

When disassembling units, the parts of which are connected with a large interference (bearing with a shaft, etc.), if the shooting causes a "seizure" of the metal at the seat, the parts are heated, for example, by pouring hot oil on the removed part. Some repair companies use induction heating installations for this purpose. The magnetic flux, passing through the mounted part, heats it up with eddy currents. After disassembling the electrical machine, its parts and assemblies are cleaned or washed.

Technological (map) process during the repair of a high-voltage synchronous electric motor weighing 2 tons. Attire, shutdown of the electric motor, withdrawal for repair, use of lifting mechanisms, slinging scheme, rigging to the repair site

Architecture, design and construction

If the work on the electric motor or the mechanism driven by it is connected with touching the current-carrying and rotating parts, the electric motor must be turned off with the implementation of the provided technical measures to prevent its erroneous switching on. Work not related to touching the current-carrying or rotating parts of the electric motor and the mechanism driven by it can be carried out on a running electric motor. When working on an electric motor, it is allowed to install grounding on any section of the cable line ...

Technological (map) process during the repair of a high-voltage synchronous electric motor weighing 2 tons. Attire, shutdown of the electric motor, withdrawal for repair, use of lifting mechanisms, slinging scheme, rigging to the repair site.

If the work on the electric motor or the mechanism driven by it is connected with touching the current-carrying and rotating parts, the electric motor must be turned off with the implementation of the provided technical measures to prevent its erroneous switching on. In this case, for a two-speed electric motor, both power circuits of the stator windings must be disconnected and disassembled.

Work that is not related to touching the current-carrying or rotating parts of the electric motor and the mechanism driven by it can be carried out on a running electric motor.

It is not allowed to remove the guards of the rotating parts of the operating electric motor and mechanism.

When working on an electric motor, it is allowed to install grounding on any section of the cable line connecting the electric motor to the switchgear section, shield, assembly. If work on the electric motor is designed for a long period of time, is not performed or is interrupted for several days, then the cable line disconnected from it must also be grounded on the side of the electric motor. In cases where the cross section of the cable cores does not allow the use of portable grounding, for electric motors with voltage up to 1000 V it is allowed to ground cable line with a copper conductor with a cross section not less than the cross section of the cable core, or connect the cable cores to each other and isolate them. Such grounding or connection of cable cores should be taken into account in operational documentation on a par with portable grounding.

Before admission to work on electric motors capable of rotation due to the mechanisms connected to them (smoke exhausters, fans, pumps, etc.), the handwheels of stop valves (gate valves, valves, gate valves, etc.) must be locked. In addition, measures have been taken to slow down the rotors of electric motors or disengage the couplings.

The necessary operations with shutoff valves must be agreed with the shift supervisor of the technological workshop, section with an entry in the operational log.

Voltage must be removed from the circuits of manual remote and automatic control of electric drives of shut-off valves, guide vanes. Posters "Don `t open! People are working", and on the keys, buttons for controlling the electric drives of the shutoff valves - “Do not turn on! People are working". On electric motors of the same type or similar in size, installed next to the engine on which the work is to be performed, posters should be postedStop! Voltage"whether they are running or stopped.

Admission to all pre-prepared workplaces, one at a time on electric motors of the same voltage, is allowed to be performed simultaneously, transferring from one workplace to another is not required. At the same time, testing or putting into operation any of the electric motors listed in the work order until the work is completed on others is not allowed.

The procedure for turning on the electric motor for testing should be as follows:the foreman removes the team from the place of work, draws up the end of work and hands over the work order to the operational personnel;

operational personnel removes the installed grounding, posters, assembles the circuit.

After testing, if it is necessary to continue working on the electric motor, the operating personnel again prepare workplace and the team along with it is re-admitted to work on the electric motor.

Work on a rotating electric motor without contact with current-carrying and rotating parts can be carried out by order.

Maintenance of the brush apparatus with the motor running is allowed by order of a group III worker trained for this purpose, subject to the following precautions:

work with the use of face and eye protection, in buttoned overalls, being careful not to capture it by the rotating parts of the electric motor;

use dielectric galoshes, carpets;

do not touch the current-carrying parts of two poles or the current-carrying and grounding parts at the same time.

The rotor rings may only be ground while the motor is rotating with pads made of insulating material.

The labor protection instructions of the relevant organizations should set out in detail the requirements for preparing the workplace and organizing safe work on electric motors, taking into account the types of electric machines used, the features of ballasts, the specifics of the mechanisms, technological schemes etc.

Organizational measures that ensure the safety of work in electrical installations are:

registration of work by an order, order or list of works performed in the order of current operation;

work permit;

supervision during work;

registration of a break in work, transfer to another place, completion of work.

Responsible for the safe conduct of work are:

issuing the order, giving the order, approving the list of works performed in the order of current operation;

responsible work manager;

allowing;

work producer;

watching;

brigade members.

This type of repair is used for engines that are in operation. A major overhaul is carried out to restore working capacity and fully restore the resource of an electric machine with the restoration or replacement of all worn or damaged components and replacement of windings. The repair of the machine is also impractical if there is significant damage to the mechanical components that cannot be repaired by our company.

A typical overhaul includes:

• operations current repair;

• checking the air gap between the stator and the rotor (if the design of the machine allows this);
• checking the axial run-up of the rotor and the gaps between the shaft neck and the sleeve of the plain bearing (if necessary, the insert is refilled);
• complete disassembly of the machine and washing of all mechanical components and parts, purging and cleaning of the collector, slip rings, brush mechanism and intact insulating parts, fault detection of components and parts;
• repair of the housing, bearing shields, magnetic circuits (welding of cracks, restoration of threaded holes, restoration of seats in the housing and shields, removal of short circuits between individual sheets of the stator and rotor cores, elimination of fluffing of sheets, restoration of pressing, repair of burnt areas with the installation of prostheses);
• shaft repair (correction of end holes, elimination of deflection, restoration of mounting holes and keyways);
• removal of old windings, production and installation of new windings from round wire, repair or production of new windings from rectangular wire and their installation, assembly and soldering (welding) electrical circuits, impregnation and drying of windings, application of cover enamels on the frontal parts;
• assembly and finishing of the machine, carrying out acceptance tests.

Repair stages

• Reception and determination of motor malfunctions:

• mechanical and electrical faults;
• reasons for failure;
• determination of the type and feasibility of repair;
• determination of the cost of work;
• conclusion of a contract for the work carried out.

Depending on the weight and dimensions, as well as the nature of the repair, the engine is either repaired on site or sent to our company. Mutual obligations of the customer and our company are regulated in the technical conditions of repair.

In what form are electric motors accepted for repair.

Acceptance for repair is carried out according to an act, in which, in addition to passport data and the estimated amount of repairs, technical requirements which the equipment must satisfy after the repair: power, voltage, energy indicators, etc. Only complete electric motors that have all the main components and parts, including old windings, are accepted for repair. All connecting and mounting parts must be dismantled by the customer. As a rule, we do not repair machines with broken housings and end shields, as well as with significant (more than 25%) damage to the magnetic circuits, although there are exceptions.

• Preparing for laying:

• dismantling of the old winding.
• determination of winding data and comparison with reference data.
• winding data optimization.
• repair of active stator and anchor iron.
  

• Winding production:

• production of groove insulation
• production of phase sections with electromechanical control
• installation of phase sections.
• execution of switching works
• bandaging and formation of frontal parts

• Preliminary tests. Winding impregnation and drying:

• checking the condition of the coiled insulation
• checking the state of interfacial and case insulation
• measurement of motor insulation resistance.
• impregnation of the winding and drying of the electric motor in an electric furnace
• winding resistance measurement.

• The motor assembly itself:

• restoration of seats.
• bearing replacement.
• crack welding.
• restoration of fasteners.
• painting.

• Final tests:

• definition of parameters Ix.x.(A)
• definition of nx.x. (rpm)
• bearing control
• control tx.x. OS.

It should be remembered:

During the overhaul, rolling bearings that have exhausted their service life are replaced (regardless of their condition). The decision to use bearings that have not exhausted their service life is made after their fault detection. At the same time, it should be remembered that the damage from a possible failure of the bearing and the associated failure (stop) of the engine is significantly greater than the cost of the bearing itself.

Round wire windings and low-voltage rectangular wire windings are usually not reused during repairs, since it is almost impossible to remove such a wire without damage. After extraction, they are transferred to the smelter. High-voltage windings made of rectangular wire can be reused after replacement of coil and body insulation at the request of the customer.

QUALITY GUARANTEE:

For electric motors in assembled and complete condition for after repair operation of the electric motor, a guarantee is provided for 12 months from the date of receipt of the electric motor from repair, subject to compliance with its further work

"RULES FOR OPERATION OF ELECTRICAL EQUIPMENT AND POWER INSTALLATIONS OF CONSUMERS".

I. What is included in the motor test:

• Resistance measurements.
• Calculation of the absorption coefficient.
• Measurement of ohmic resistance in phases.
• Checking the motor at idle.
• Correspondence of no-load current and frequency. rotation passport values.
• Calculation of the transformation ratio.
• Check bearings for heat.
• Motor vibration check.
• Rotor wire break test.
• High voltage tests (as required by the customer).

II. What is included in the restoration of the appearance.

• Removing old paint.
• Straightening of the hull and hinged parts.
• Puttying potholes, dents.
• Cleaning the shaft from corrosion.
• Preservation or painting of the shaft.
• Motor painting.
• Installation of a rating plate (mandatory!!!).
• The output ends of the windings are marked in accordance with the standard, and a new shield is installed on the machine body indicating our company (which carried out the repair), the date of issue from the repair and the technical data of the electric motor in accordance with the standards.

III. What is included in the current repair:

This type of repair is used for machines that are in operation or in reserve. Current repairs are carried out at the place of installation of the electric motor with its stop and shutdown by your maintenance electrical personnel. If current repairs require special complex devices and considerable time, then it is carried out by the personnel of an electrical repair or specialized enterprise.

1. Disassembly / assembly.

2. Defective motor.

During fault detection, we carry out a visual inspection of the units and parts of the machine, carry out the necessary measurements and tests, determine the integrity of individual parts and assembly units, the condition of the working surfaces to determine the amount of necessary repairs. If the assembly unit is not damaged, it is not disassembled. Disassembly must be carried out using a special tool so as not to damage parts and assembly units.

3. Current repair of the stator:

• Flushing of electric motor parts:
• Washing the coils of the motor winding.
• Drying of the motor stator.
• Replacement and restoration of output ends.
• Restoration of the connection scheme of the winding coils.
• Checking the resistance of case and phase-to-phase insulation.
• Impregnation with varnish.
• Coloring.
• Replacement of insulators.

4. Maintenance of the rotor:

• Washing the coils of the rotor winding.
• Drying of the rotor of the electric motor.
• Bandage replacement.
• Wedging with the manufacture of new wedges.
• Restoration of the connection diagram of the rotor winding coils.
• Grooving/replacing contact rings.
• Checking the resistance of case and phase-to-phase insulation.
• Checking the rotor for breakage.
• Check for interturn short circuits.
• Impregnation with varnish.
• Coloring.

5. Rotor balancing.

6. Replacement of bearings.

7. Mechanical repair:

• Repair / replacement of the brush apparatus.
• Restoration of seats for bearings on shields.
• Restoration of seats for bearings on the shaft.
• Manufacture / replacement of new shields, bearing caps.

CALCULATION OF THE COST OF THE FULL COMPLEX OF WORKS ON REPAIR OF ELECTRIC MOTORS IS CALCULATED ON CONTRACTUAL CONDITIONS.

We always carry out repairs so that the required level of operational reliability is ensured after it, and technical indicators your equipment meets the standards and norms.

1.4 Routing repair and maintenance of an asynchronous motor with a squirrel-cage rotor

Security measures

The electric motor must be de-energized, the AB is turned off, grounding is installed, posters are hung out. Apply portable grounding to the input ends of the electric motor cable. Secure the work site. Work with PPE. Work with trusted instruments and tested power tools and fixtures.

The composition of the brigade

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

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3.11 Technological map of the current repair of asynchronous electric motors 6kV PEN.

After assembly, make a control measurement of the motor insulation resistance and absorption coefficient with a 2500V megohmmeter. The insulation resistance must be at least 40 MΩ, the absorption coefficient must be at least the value specified in clause 1.3.2.

3.12 Technological map of the current repair of asynchronous electric motors 6 kV TsN.

After assembly, make a control measurement of the motor insulation resistance and absorption coefficient with a 2500V megohmmeter. The insulation resistance must be at least 40 MΩ, the absorption coefficient must be at least the value specified in clause 1.3.2. When assembling, check the condition of the oil indicators, for which:

a) clean the oil gauges from external contaminants;

b) unscrew the damping bolt from the oil gauge, clean the internal cavity of the damping chamber of the oil gauge and the damping bolt from contamination; install a new sealing head gasket of the stilling bolt and screw the bolt back. It is allowed, if necessary, to lubricate the sealing gasket of the head of the stilling bolt with a thin layer of oil-resistant sealant KLT-75;

c) check the absence of plaque on the internal surfaces of the glass, which makes it difficult to visually control the oil level, mechanical damage in the form of cracks and chips; clean the “breathing” hole in the upper cover of the oil indicator with a soft wire;

d) blow out the oil gauges with compressed air at a pressure of no more than 2 kg/cm 2 to check the patency of the oil gauge with control by the air pressure coming out through the “breathing” hole;

If traces of oil leaks through the seals of the oil gauge, plaque on the inner surface of the glass, which makes it difficult to visually control the oil level, foreign particles (sealant residues, etc.) or other defects, or other defects, the oil gauge is completely disassembled and the defects are eliminated with subsequent assembly. In this case, the resting bolt is screwed into place last, after the sealant that seals the glass has hardened. After assembly, the oil indicator is installed on the oil tank with the inspection hole of the small indicator housing in the direction opposite to the motor housing, after which the oil indicator is re-checked according to item d).

When installing the floorboards of the upper part of the body and the connecting jumpers between the floorboards, use sealant (paint) in the threaded connection of the jumpers as a countermeasure.

3.13 Technological map of the current repair of asynchronous electric motors 6kV (NR).

3.14 Technological map of the current repair of the backup exciter DAZ-18-10-6 (U3), GSP-2000-1000.

When replacing a bearing, it must be pressed off the shaft using a screw puller. The new bearing is washed from conservation grease in B-70 gasoline. Heat the bearing in an oil bath or with an inductor to a temperature of 90°C and press onto the shaft. Refer to Appendix 20 for bearing mounting recommendations. Shaft fit is tight. Then the bearing is filled with grease (LITOL-24, SVEM, TsIATIM-201). After assembly, make a control measurement of the motor insulation resistance and absorption coefficient with a 2500V megohmmeter. The insulation resistance must be at least 40 MΩ, the absorption coefficient must be at least the value specified in clause 1.3.2.