Electric motor repair services: rewinding of the armature and worn out phase winding

Electric motors are complex devices that provide the operation of many mechanisms. Their basic principle of action is to convert electricity into mechanical energy. From time to time, such engines fail. To solve the problem, rewinding and repair of electric motors is often required, which can be carried out independently or with the assistance of specialists.

Types of electric motors

The category of electric motors includes a large number of different devices that convert electricity into mechanical energy. All of them have certain features and characteristics, in accordance with which they are combined into separate types.

DC motors are used to create variable drives characterized by high rotation uniformity and overload capacity. They are used to equip polymer plants, drilling rigs, auxiliary elements for excavators, painting and finishing and lifting and transport equipment.

Servomotors that use negative feedback belong to a subtype of devices operating at the expense of direct current. They are very powerful and can pick up a high speed of rotation of the shaft, controlled by software.

More common are AC motors, which have found application in both industrial and domestic spheres. Most household appliances (washing machines, cooker hoods, refrigerators, etc.) are powered by these motors. Large industrial devices such as compressors, winches, fans, pumps cannot do without them. Such a wide range of operation is due to the reliability of the design, ease of use and the economic benefits of the production of motors.

Another common type of electric motors are ball motors. The mechanical energy received in them is of a discrete nature. They are distinguished by their compact size and high productivity, therefore they are well suited for electronics and office equipment.

A feature of linear-type units is the rectilinear movement of the stator and rotor relative to each other. Their use guarantees efficiency and reliability of the mechanisms. These qualities are ensured due to the almost complete elimination of mechanical transmission.

Synchronous motors are characterized by a constant speed of operation, therefore they are used in fans, compressors and pumps. The rotor speed and the magnetic field are the same.

Motors in which these values ​​differ are called asynchronous. With the same stator arrangement, they can have different windings and phase or squirrel-cage rotors.

Number of phases

One of the important properties of alternating current is the ability to form an alternating magnetic field and induce current. Thanks to this, AC motors were created. The role of the rotor in such a device is played by a metal cylinder with slots. At an angle to the axis of rotation, conductive conductors are fixed in them, united by rings at the ends of the cylinder. There is a backflow in the rotor and a magnetic field repels it from the stator.

An important element of AC electric motors is the stator winding. Depending on the number of such windings electric motors are:

• Single-phase. The vector of the repulsive force in them passes through the axis of rotation, so they cannot start on their own. In order for the engine to start, you need to provide a starting jerk or turn on a separate starting winding, which will create an additional moment of force capable of displacing the total vector relative to the axis of the armature.
• Two-phase. They contain two windings located at a certain angle equal to the phase displacement angle. Due to this, the decrease in the tension of one winding and the increase in the other occur synchronously. The two-phase mechanism starts independently, it is used in single-phase power grids. The second phase is connected through a phase-shifting element, the role of which is played by a capacitor.
• Three-phase. They are considered the most perfect, since they easily change the order of switching on the phase windings, which contributes to a change in the direction of movement of the magnetic field and the rotor. This is called motor reversal.

AC collector devices are suitable for applications where high frequency rotations are required. Such motors have a low starting current, so when they are started, the network does not receive a large load. The revolutions in them are easily controllable, the starting torque depends not on the revolutions, but on the current.

To ensure these properties, a synchronous motor must be equipped with a rotor with a stacked core, several windings and a collector with complex balancing. The use of such parts significantly increases the cost of the finished product.

Common malfunctions

The electric motors manufactured at the factory are fully functional, their performance has been tested and documented. But sometimes a new device refuses to work at the first start. This can be caused by breakdowns during loading, transportation, storage or installation. The sharp shocks, strong shocks and vibrations that the equipment is subjected to during this time often lead to its premature failure.

Engines are most often stored in cold rooms or in open areas. This can corrode the elements. Rust enters the motor winding and destroys its insulation. Violation of the coil insulation leads to short circuits, the device overheats, the rotation of the rotor becomes uneven, an imbalance of the tension forces of the rotor to the stator occurs. In this case, a major overhaul is required. engines.

In collector motors, problems can arise due to a violation of the brush-collector assembly, which manifests itself in the form of strong sparking and an all-round fire on the collector.

There are many motor malfunctions for different reasons. Here are examples of some of them:

1. When connected to the network, the rotor remains stationary. This happens due to the absence or insufficient voltage at the input terminals. It is required to ensure its supply, having previously checked the supply line and eliminated the damage.
2. When voltage is applied, the device hums and heats up a lot, and the rotor does not rotate. The reason may be the destruction of the bearing, the grazing of the rotor against the stator, the jamming of the shaft. Disconnect the motor shaft from the mechanism shaft and turn on the motor. If it does not start rotating, send it in for repair.
3. The running engine stops. This happens when the protection is triggered or the voltage is not supplied. It is necessary to eliminate the breakdown of the supply network or determine why the protection worked.

Occasionally, the operating device may become very hot due to overload, unstable voltage, too high air temperature or poor ventilation of the motor. To prevent damage, you need to lower the ambient temperature, stabilize the current and clean the ventilation ducts of the air supply.

Rewind process

Prolonged operation of an electric motor leads to wear of the existing winding in it. In such a situation, DC electric motors are repaired, implying their rewinding, which is also resorted to in order to change the speed of rotation of the device or the voltage in it.

The documentation supplied with the electric motor indicates the frequency with which it must be rewound. For low-voltage devices, it is about 6-7 years, for high-voltage devices - 25 years. However, there are situations when you need to conduct an emergency rewind. To do this, you will have to contact a repair shop, where are qualified specialists:

1. They will disassemble the motor, disconnect the fan and anchor.
2. Remove the old winding, sell the stator.
3. They will measure the length of the stator and the width of the insulation of the grooves.
4. They will cut out the necessary elements, remove the spool template.
5. Coils will be wound with a certain number of evenly distributed turns.
6. They will put the coils in the grooves, laying an insulating material between them.
7. Carry out a frontal harness.
8. Using the circuit, the coils will be connected by welding or soldering the ends.
9. The grooves will be tamped and the stator winding will be ringed.
10. Final tests of the equipment will be carried out.

Today there are organizations that provide services not only for replacing the phase winding, but also for rewinding the armature. During such a repair wizards carry out the following actions:

1. Dismantle the winding, remove and clean the collector.
2. Grooves are made in the armature to accommodate the ends of the wound coil.
3. A special cardboard sleeve is inserted into the groove.
4. Winding is performed. The turns are wound counterclockwise until the grooves are completely filled.
5. Cotton insulation impregnated with epoxy resin or varnish is laid on top.
6. Check the armature with an ammeter and grind it.
7. On a special machine, the inter-lamellar space is milled.
8. Balance, clean and grind the anchor.
9. Recheck for breaks or short circuits.

After completion of the repair, the electric motor is assembled. Then it is necessarily tested for closure.

Some companies offer their customers additional services for repairing tachogenerators, replacing brush assemblies, lubricating bearings and completing missing parts. This allows for a longer and more efficient operation of the motor after repair.

DIY repair

The services of organizations specializing in the repair and rewinding of engines are not cheap, so many decide to repair them with their own hands. In order for self-repair to be successful, it is necessary to ensure the exact number of turns, otherwise it will be fraught with their burning due to the difference in currents. It is necessary to avoid overlapping conductors, trying to maintain an equal distance between the turns. This will make it easier to fit the latter into the stator slots.

To correctly place the turns in the grooves, it is worth using a rammer - a device in the form of a blade, the thickness of which coincides with the dimensions of the grooves. To cover the stator, it is necessary to use electrical cardboard, and the arrows should be made of insulating material.

The ends remaining after laying the insulation must be assembled according to the "star" scheme, the winding must be connected with a soldering iron. The soldering points must be protected with insulating tubes.

The front parts of the windings must be fixed with a strapping wire or cord thread. Parts protruding from the housing of the grooves and the stator must be well tamped.

After completing all repair work, it is necessary to correctly assemble the electric motor. This is done in the reverse order compared to disassembly.