The most difficult and important issue in the repair of electric motors is determining the suitability of serviceable windings for further operation and establishing the type and required scope of repair of faulty windings.

Determination of winding suitability

Typical damage to windings is insulation damage and loss of integrity electrical circuits. The insulation condition is judged by indicators such as insulation resistance, high voltage insulation test results, deviations of the DC resistance values ​​of individual windings (phases, poles, etc.) from each other, from previously measured values ​​or from factory data, as well as by the absence of signs of interturn short circuits in individual parts of the winding. In addition, the assessment takes into account the total operating time of the electric motor without rewinding and its operating conditions.

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

A sign of thermal aging of insulation is its lack of elasticity, fragility, tendency to crack and break under fairly weak conditions. mechanical influences. The greatest aging is observed in areas of increased heating, remote from the outer surfaces of the insulation. In this regard, to study the thermal wear of winding insulation, it is necessary to open it locally to its full depth. Sites are selected for research small area, located in areas of greatest insulation aging, but accessible for reliable restoration of insulation after opening. To ensure the reliability of the study results, there must be several places where the insulation was opened.

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

Signs of unreliable insulation are also the penetration of oil contaminants into the thickness of the insulation and loose pressing of the winding into the groove, which may cause vibration movements of the conductors or the sides of the sections (coils).

To determine winding faults, special instruments are used. Thus, to identify turn short circuits and breaks in the windings of machines, to check the correct connection of the windings according to the diagram, to mark the output ends of the phase windings of electrical machines, an EL-1 electronic device is used. It allows you to quickly and accurately detect a fault during the manufacturing of windings, as well as after laying them in the grooves; The sensitivity of the device allows you to detect the presence of one short-circuited turn for every 2000 turns.

If only a small part of the windings have faults and damage, then partial repairs are prescribed. However, in this case it must be possible to remove faulty parts of the winding without damaging serviceable sections or coils. Otherwise it is more appropriate major renovation with complete replacement of the winding.

Repair of stator windings

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

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

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

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

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

Having wound the coil groups, they are tied with tape and begin to be laid in the grooves. To insulate the windings from the housing in the grooves, groove sleeves are used, which are a single-layer or multi-layer U-shaped bracket made of material selected depending on the insulation class. Thus, for insulation class A, electric cardboard and varnished fabric are used, for heat-resistant windings - flexible micanite or glass micanite.

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

The block diagram of the algorithm and flow chart for repairing the random winding of an asynchronous electric motor is given below.

Winding manufacturing technology:

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


2. Clean the stator grooves from dust and dirt. Insert groove insulation over the entire length into all grooves.


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


4. Place two plates into the groove to protect the wire insulation from damage when laying them. Insert a coil group into the stator bore; straighten the wires with your hands and place them in the grooves. Remove the plates from the groove. Distribute the wires evenly in the groove with a fiber stick. Place an interlayer insulating spacer into the groove. Use a hammer (hatchet) to place the laid coil on the bottom of the groove. For double-layer winding, place the second coil in the groove.


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


6. Place the wedge into the groove and use a hammer to wedge it.
   Using needle-nose pliers, cut off the ends of the wedges protruding from the ends of the stator, leaving 5 - 7 mm ends on each side. Cut off the protruding parts of the insulating gaskets.


7. Place insulating spacers in the frontal parts of the windings between adjacent coils of two groups of different phases laid side by side.
   Bend the frontal parts of the winding coils by 15-18° with hammer blows towards the outer diameter of the stator. Observe the smooth bend of the coil wires where they exit the groove.

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

In the winding manufacturing technology, some generalizations regarding details have been made.

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

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

Rice. 105. Device for driving wedges into grooves

After laying the winding in the grooves, the edges of the groove sleeves are bent and wooden or textolite wedges are driven into the grooves. To protect the wedges 1 from breakage and protect the frontal part of the winding, a device is used (Fig. 105), consisting of a bent sheet steel frame 2, into which a steel rod 3 having the shape and size of a wedge is freely inserted. The wedge is inserted with one end into the groove, the other into the cage and driven with hammer blows on the steel rod. The length of the wedge should be 10 - 20 mm greater than the length of the core and 2 - 3 mm less than the length of the sleeve; Wedge thickness - at least 2 mm. The wedges are boiled in drying oil at a temperature of 120-140 C for 3-4 hours.

After placing the coils in the grooves and wedging the windings, the circuit is assembled, starting with the serial connection of the coils into coil groups. The beginnings of the phases are taken to be the conclusions of the coil groups coming out of the grooves located near the input panel of the electric motor. The terminals of each phase are connected after stripping the ends of the wires.

Having assembled the winding diagram, check the electrical strength of the insulation between the phases and on the housing. The absence of turn short circuits in the winding is determined using the EL-1 apparatus.

Replacing a coil with damaged insulation

Replacing a coil with damaged insulation begins with removing the insulation of the inter-coil connections and bandages that attach the frontal parts of the coils to the bandage rings, then remove the spacers between the frontal parts, unsolder the coil connections and knock out the groove wedges. The coils are heated with direct current to a temperature of 80 - 90 °C. The upper sides of the coils are lifted using wooden wedges, carefully bending them inside the stator and tying them to the frontal parts of the laid coils with keeper tape. After this, the coil with damaged insulation is removed from the grooves. The old insulation is removed and replaced with new.

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

The technology for winding rigid coils is much more complex than loose coils. The wire is wound onto a flat template, and the grooved parts of the coils are stretched to an equal distance between the grooves. The coils have significant elasticity, therefore, to obtain precise dimensions, their grooved parts are pressed, and the frontal parts are straightened. The pressing process involves heating under pressure coils coated with bakelite or glypthal varnish. When heated, the binders soften and fill the pores of the insulating materials, and after cooling they harden and hold the wires of the coils together.

Before laying in the grooves, the coils are straightened using devices. The finished coils are placed in the grooves, heated to a temperature of 75 - 90 ° C and pressed with light blows of a hammer on a wooden sediment strip. The front parts of the coils are also straightened. The lower sides of the frontal parts are tied to the bandage rings with a cord. Gaskets are hammered between the frontal parts. The prepared coils are lowered into the slots, the slots are jammed and the inter-coil connections are connected by soldering.

Repair of rotor windings

The following types of windings are used in asynchronous motors: “squirrel cages” with the rods filled with aluminum or welded from copper rods, coil and rod windings. The most widely used are “squirrel cages” filled with aluminum. The winding consists of rods and closing rings on which the fan wings are cast.

To remove a damaged “cage,” use smelting it or dissolving aluminum in a 50% caustic soda solution for 2–3 hours. Fill a new “cage” with molten aluminum at a temperature of 750–780 °C. The rotor is preheated to 400-500 °C to avoid premature solidification of aluminum. If the rotor is poorly pressed before casting, then during casting aluminum can penetrate between the iron sheets and short them, increasing losses in the rotor from eddy currents. It is also unacceptable to press the iron too hard, as breaks of the newly poured rods may occur.

Repairs to copper rod squirrel cages are most often done using old rods. After sawing the connection of the “cage” rods on one side of the rotor, remove the ring, and then do the same operation on the other side of the rotor. Mark the position of the ring relative to the grooves so that the ends of the rods and the old grooves coincide during assembly. The rods are knocked out by carefully hitting the aluminum chocks with a hammer and straightened.

The rods should fit into the grooves with a light blow of a hammer on the textolite tamper. It is recommended to simultaneously insert all the rods into the grooves and tap diametrically opposite rods. The rods are soldered one by one, after preheating the ring to a temperature at which copper-phosphorus solder easily melts when brought to the joint. When soldering, make sure to fill the gaps between the ring and the rod.

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

After establishing the causes and nature of the malfunction, the issue of partial or complete rewinding of the rotor is decided. The bandage wire is unwound onto a drum. After removing the bandages, solder the solders in the heads and remove the connecting clamps. The frontal parts of the rods of the upper layer are bent from the side of the contact rings and these rods are removed from the groove. Clean the rods from old insulation and straighten them. The grooves of the rotor core and winding holder are cleaned of insulation residues. The straightened rods are insulated, impregnated with varnish and dried. The ends of the rods are tinned with POS-ZO solder. The groove insulation is replaced with a new one, placing boxes and gaskets on the bottom of the grooves with even protrusion from the grooves on both sides of the core. After graduation preparatory work start assembling the rotor windings.

Rice. 106. Laying the rotor winding coil:
a - coil; b - open rotor slot with winding installed.

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

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

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

Often in repair practice, bandages are made of fiberglass and baked together with the winding. The cross-section of a fiberglass bandage is increased by 2 - 3 times relative to the cross-section of a wire bandage. The end turn of the fiberglass is attached to the underlying layer during the drying process of the winding during sintering of the thermosetting varnish with which the fiberglass is impregnated. With this bandage design, elements such as locks, brackets and under-bandage insulation are eliminated. The devices and machines for winding fiberglass bandages are the same as for winding wire ones.

Repair of armature windings

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

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

In the armatures of machines with a power of up to 15 kW with a semi-closed groove shape, random windings are used, and for machines more power with an open slot shape - coil windings. The coils are made of round or rectangular wire. The most widely used template armature windings are made from insulated wires or copper busbars insulated with varnished cloth or mycalente.

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

The insulated coil is placed into the grooves of the armature core. They are secured in them with special wedges and the wires are connected to the collector plates by soldering with POS-30 solder. The wedges are pressed from heat-resistant plastic materials - isoflex-2, trivolterma, PTEF (polyethylene terephthalate) films.

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

All work on dismantling bandages, applying bandages made of wire or glass tape on the armatures of DC machines is carried out in the same order as when repairing the windings of phase rotors of asynchronous machines.

Repair of pole coils

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

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

The coils of additional poles are repaired, restoring the insulation of the turns. The coil is cleaned of old insulation and placed on a special mandrel. The insulating material is asbestos paper 0.3 mm thick, cut into frames according to the size of the turns. The number of gaskets must be equal to the number of turns. On both sides they are coated with a thin layer of bakelite or glypthal varnish. The coil turns are spread apart on a mandrel and spacers are placed between them. Then they tighten the coil with cotton tape and press it. The coil is pressed on a metal mandrel, onto which an insulating washer is placed, then the coil is installed, covered with a second washer and the coil is compressed. By heating the welding transformer to 120 C, the coil is further compressed. Cool it in the pressed position to 25 - 30 °C. After removal from the mandrel, the coil is cooled, coated with air-drying varnish and kept at a temperature of 20 - 25 ° C for 10 - 12 hours.

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

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

Drying, impregnation and testing of windings

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

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

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

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

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

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

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

The impregnating varnish is supplied to the reservoir from a container located in another, non-fire hazardous room. Varnish and solvents are toxic and fire hazardous and, in accordance with labor protection rules, work with them must be carried out in safety glasses, gloves, and a rubber apron in rooms equipped with supply and exhaust ventilation.

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

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

In the process of manufacturing and repairing machine windings, necessary tests coil insulation. The test voltage must be such that during testing defective areas insulation and the insulation of serviceable windings was not damaged. Thus, for coils with a voltage of 400 V, the test voltage of a coil not removed from the grooves for 1 minute should be equal to 1600 V, and after connecting the circuit during partial repair of the winding - 1300 V.

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

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 personal protective equipment. Work with verified instruments, mechanisms and proven power tools and accessories. All operations during a major overhaul to repair components and parts of an electric motor 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 shall not be obstructed, but shall prevent unauthorized access in a potentially dangerous manner. danger zone. 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 guards on a running 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

Machine for dynamic balancing rotor

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.

This type of repair is used for engines in service. Major repairs are carried out to restore the functionality and complete restoration of the service life of an electrical machine with the restoration or replacement of all worn or damaged components and the replacement of windings. Repairing a machine may not be practical if there is significant damage to mechanical components that cannot be repaired by our company.

A typical overhaul scope includes:

• maintenance operations;

• checking the air gap between the stator and the rotor (if the machine design allows this);
• checking the axial run of the rotor and the gaps between the shaft journal and the plain bearing liner (if necessary, the liner is refilled);
• complete disassembly of the machine and washing of all mechanical components and parts, purging and cleaning of the commutator, slip rings, brush mechanism and intact insulating parts, defect detection of components and parts;
• repair of the housing, bearing shields, magnetic circuits (welding cracks, restoring threaded holes, restoring seats in the housing and shields, removing short circuits between separate sheets stator and rotor cores, elimination of fluffing of sheets, restoration of pressing, repair of burnt areas with 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 diagrams, impregnation and drying of windings, application of coating enamels to the frontal parts;
• assembly and finishing of the machine, carrying out acceptance tests.

Repair stages

• Reception and determination of electric motor faults:

• mechanical and electrical faults;
• reasons for failure;
• determining the type and feasibility of repairs;
• determining the cost of work;
• conclusion of a contract for the work performed.

Depending on the weight and dimensions, as well as the nature of the engine repair, they are either repaired on site or sent to our facility. 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 repairs is carried out according to an act, which, in addition to passport data and the expected scope of repairs, indicates technical requirements requirements that the equipment must satisfy after 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 installation parts must be removed by the customer. As a rule, we do not repair machines with broken housings and bearing shields, as well as with significant (more than 25%) damage to magnetic circuits, although there are exceptions.

• Preparation for installation:

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

• Winding production:

• production of groove insulation
• production of phase sections with electromechanical control
• laying of phase sections.
• performing switching work
• bandaging and shaping of frontal parts

• Preliminary tests. Impregnation and drying of the winding:

• checking the condition of the turn insulation
• checking the condition of interphase and body insulation
• measuring the insulation resistance of an electric motor.
• impregnation of the winding and drying of the electric motor in an electric furnace
• winding resistance measurement.

• The electric motor assembly itself:

• restoration of seats.
• bearing replacement.
• welding of cracks.
• restoration of fastening connections.
• painting.

• Final tests:

• determination of parameters Ix.x.(A)
• definition n x.x. (rpm)
• bearing control
• control t x.x. oS.

Things to remember:

During a major 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 they have been defective. It should be remembered that damage from possible refusal bearing and the associated engine failure (stoppage) is significantly more than the cost of the bearing itself.

Windings made of round wire and low-voltage windings made of rectangular wire are, as a rule, not reused during repairs, since it is almost impossible to remove such a wire without damage. After extraction, they are transferred to smelting. High-voltage windings made of rectangular wire can be reused after replacing the turn and body insulation at the request of the customer.

QUALITY GUARANTEES:

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

“RULES FOR THE OPERATION OF ELECTRICAL EQUIPMENT AND POWER INSTALLATIONS FOR CONSUMERS”.

I. What is included in the electric motor test:

• Resistance measurements.
• Calculation of absorption coefficient.
• Measurement of ohmic resistance by phase.
• Checking the electric motor at idle speed.
• Correspondence between no-load current and frequency. rotation to the passport values.
• Calculation of transformation ratio.
• Checking bearings for heating.
• Checking for vibration of the electric motor.
• Check for broken rotor conductors.
• High voltage tests (as required by the customer).

II. What is included in the restoration of appearance.

• Removing old paint.
• Straightening the body and attached parts.
• Puttying potholes and dents.
• Cleaning the shaft from corrosion.
• Preservation or painting of the shaft.
• Painting the electric motor.
• Installation of a nameplate (required!!!).
• 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 (who carried out the repair), the date of release from repair and the technical data of the electric motor in accordance with the standards.

III. What is included in current repairs:

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

1. Disassembly/assembly.

2. Defect of the electric motor.

During defect detection, we carry out a visual inspection of the components 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 volume 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:

• Washing electric motor parts:
• Cleaning the motor winding coils.
• Drying the motor stator.
• Replacement and restoration of output ends.
• Restoring the connection diagram of the winding coils.
• Checking the resistance of housing and phase-to-phase insulation.
• Impregnation with varnish.
• Coloring.
• Replacement of insulators.

4. Rotor maintenance:

• Washing the rotor winding coils.
• Drying the electric motor rotor.
• Replacing bandages.
• Re-wedging with the production of new wedges.
• Restoring the connection diagram of the rotor winding coils.
• Grooving/replacing slip rings.
• Checking the resistance of housing and phase-to-phase insulation.
• Checking the rotor for breaks.
• Checking for interturn short circuits.
• Impregnation with varnish.
• Coloring.

5. Rotor balancing.

6. Replacement of bearings.

7. Repair of mechanical parts:

• Repair/replacement of brush apparatus.
• Restoration of bearing seats on shields.
• Restoration of bearing seats on the shaft.
• Manufacturing/replacement of new shields and bearing caps.

CALCULATION OF THE COST OF THE FULL SET OF WORKS ON REPAIR OF ELECTRIC MOTORS IS CALCULATED ON CONTRACTUAL TERMS.

We always carry out repairs so that after the repair the required level of operational reliability is ensured, and the technical performance of your equipment complies with standards and norms.

1.4 Technological map for repair and maintenance of an asynchronous motor with a 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.

Adaptive vector control system of a sensorless asynchronous electric drive

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The control circuit for an asynchronous motor using a magnetic starter (Figure 6) includes a magnetic starter consisting of a KM contactor and two KK thermal protection relays built into it...

Asynchronous motors in electric drive systems

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The initial data for drawing up the schedule are: * The repair cycle is a repeating set various types planned repairs carried out in a given sequence through certain...

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Organization of maintenance and repair of friction press 4KF-200

Defects: 1. Curvature of the shaft axis 2. Shells on the shaft journals w160 mm, shell depth h=4 mm Figure 2.10 - Sketch of the screw shaft Table 2.7 - Technological map for repairing the screw shaft Name of operations and works Sketch of the shaft Device...

Project of an automated electric drive for a freight elevator

The most accurate mechanical characteristic of an asynchronous motor is the catalog dependence M(S), and only in the absence of a catalog dependence do we have to resort to approximate calculations...

Development of a mini-shop for wire drawing

The system of maintenance and repair (MRO) of wire drawing equipment provides for routine and major repairs of equipment in a certain sequence...

Development technological process restoration of the crankcase cover part of the TDT-55 tractor gearbox

Defect No. No. Operation Name and content of the operation Equipment Tool equipment Note 4 005 Boring: bore the hole to a size of 22.40 mm. Boring machine 2E78PN Cutters from Elbor-R of suitable diameter 5-10 min...

Repair technology and maintenance of an asynchronous motor with a squirrel-cage rotor

An asynchronous machine is an electric machine alternating current, the rotor speed of which is not equal (in motor mode less) to the rotation speed magnetic field, created by the stator winding current...

Control of asynchronous motors

Rice. 3. Starting diagram of an asynchronous motor with a wound rotor Using the diagram of an asynchronous motor (Fig.), we will consider starting in two stages, which is carried out using relay contactor equipment...

Protected workshop lighting. Statement and linear schedule of repair work. Technological map for AC motor repair. Using a machine for dynamic balancing of rotors. Removing the rotor from the stator.

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