Motor winding fault analysis and processing method

The winding is an integral part of the motor. Aging, moisture, heat, erosion, foreign matter intrusion, and external force will cause damage to the windings. Motor overload, undervoltage, and overvoltage, and phase loss operation can also cause winding failure. Winding faults are generally divided into winding grounds, short circuits, open circuits, and wiring faults. Now explain the phenomenon of failure, the reasons for the cause and the inspection method.

Refers to grounding caused by damage to the windings and the core or to the insulation of the enclosure.

1, the phenomenon of failure

Enclosure electrification, control circuit out of control, winding short-circuit heat, resulting in the motor can not operate normally.

2, the reason

Insulation resistance decreases due to moisture in the windings; Long-term overload operation of the motor; Corrosion of harmful gases; Ingress of metal foreign materials into the windings to damage the insulation; Insulation damage to the stator winding when rewinding the iron cores; End caps of the windings touch the base; Insulation burns due to stator and rotor friction Leading line insulation damage collided with the shell; overvoltage (such as lightning) makes insulation breakdown.

4. Treatment method

(1) The grounding of windings caused by moisture should be dried first. When it is cooled to about 60-70°C, it is poured with insulating paint and dried.

(2) When the insulation at the end of the winding is damaged, re-insert the insulation at the grounding, paint, and then dry.

(3) When the winding grounding point is in the slot, the winding should be re-wound or some of the winding components should be replaced.

After the application of different megohmmeters to measure, meet the technical requirements can be.

Due to excessive motor current, excessive power supply voltage fluctuations, single-phase operation, mechanical bumps, poor manufacturing, etc., insulation damage is caused, and the windings are short-circuited by windings, short-circuited between windings, short-circuit between windings, and short-circuit between windings.

1. Failure phenomenon

The magnetic field of ions is unevenly distributed, and the three-phase current is unbalanced, which makes the vibration and noise of the motor intensify. In severe cases, the motor cannot start, and a large short-circuit current is generated in the short-circuit coil, causing the coil to rapidly heat and burn.

2. Cause

Long-term overload of the motor causes insulation aging to lose insulation; damage caused by inserting wires; insulation breakdown caused by dampening of windings; lower insulation resistance of the windings; insulation damage at the end and interlayer insulation material; or insulation damage at the end connection wires Overvoltage or lightning strikes the insulation breakdown; rotor and stator winding ends rub against each other to cause insulation damage; metal foreign objects fall into the motor and there is too much oil.

4. Short-circuit processing method

(1) The short-circuit point is at the end. Insulating materials can be used to separate the short-circuit points, and the insulated wires can also be re-packaged, and then painted and re-dried.

(2) Short circuit in the slot. After it is softened, find the short-circuit point repair, put it back into the slot, and then paint and dry it.

(3) For each phase winding with less than 1/12 of the short circuit turns, cut off all the short-circuit lines when the number of turns is connected, and connect the conducting parts to form a closed circuit to supply them for emergency use.

(4) When the number of turns in the winding short-circuit point exceeds 1/12, the rewinding must be completely removed.

Due to poor welding or the use of corrosive fluxes, the welds may not be removed after welding. They may cause pot welding or loosening. Wires that are subject to mechanical stress or a short circuit during a collision, short circuits, and ground faults can cause the wires to burn out. When one or several wires in the wire are short-circuited, the other wires increase in temperature due to the increase of the current, causing the winding to heat and open circuit. It is generally divided into a phase winding end breakage, a turn-to-turn short circuit, a parallel branch circuit break, multiple conductors and a burnout, and a rotor break cage.

1. Failure phenomenon

The motor cannot start, the three-phase current is unbalanced, there is abnormal noise or vibration, and the temperature rise exceeds the allowable value or smoke.

2. Cause

(1) Break or create quality problems during inspection and maintenance.

(2) Wrong welding of each component of the winding, pole (phase) group, and wiring and lead wires such as the lead wire, long-term operation overheating and desoldering.

(3) The windings are damaged or broken due to mechanical and electromagnetic forces.

(4) The windings are seriously scorched or broken due to short circuit and grounding between turns.

4. Open circuit processing method

(1) When the circuit is broken at the end, it shall be firmly welded after being connected, covered with insulating material, put on the insulating tube, tied and then dried.

(2) Windings New windings should normally be replaced due to severe burn-out of windings due to interturn, phase-to-phase short circuits and grounding.

(3) Emergency handling is performed for the break point in the groove, which belongs to a small number of break points. A breakout point method is used to find the break point, and it is used after the winding is disconnected and the insulation is qualified.

(4) The caged cages can be repaired by welding, cold-bonding or strip change.

Winding connection error causes incomplete rotating magnetic field, causing difficulty in starting, unbalanced three-phase current, large noise and other symptoms. If it is not treated in time, it will burn out the winding. There are mainly the following situations: One or more coils in a certain polar phase are embedded or connected head to tail; the polar (phase) group is reversed; the winding of one phase is reversed; the parallel winding branch of multiple paths is connected incorrectly; "Y" wrong connection.

1, the phenomenon of failure

The motor cannot start, the no-load current is too large or the imbalance is too large, the temperature rises too fast or there is severe vibration and there is a lot of noise, and the fuse is blown.

2, the reason

Misconnect the "â–³" type into "Y" type; one phase of the three phase winding is reversed during maintenance; the decompression start is inappropriate selection of tap position or internal wiring error; the winding connection is wrong when the new motor is offline; The motor failed to judge correctly.

3 maintenance methods

(1) Ball method. If the ball rotates and rolls along the inner circumferential surface of the stator, it means that it is correct, otherwise the winding may be miswired.

(2) Compass method. If the windings are not connected incorrectly, then in one phase winding, when the compass passes through the adjacent pole (phase) group, the polarity of the fingers should be reversed, and the polar (phase) groups of adjacent phases in the three-phase windings are also On the contrary, if the polarity direction is constant, it indicates that there is a pole (phase) group reverse connection; if it is indefinite, there is a reversed coil in the phase group.

(3) Multimeter voltage method. According to the wiring diagram, if there is no indication on the two measured voltmeters, or if there is one reading and one reading at a time, it indicates that the windings are connected reversely.

(4) Common methods include dry battery method, milliammeter remanence method, and motor steering method.

4. Treatment method

(1) If a coil or coil group is connected reversely, the no-load current has a large imbalance and should be returned to the factory for repair.

(2) Leading line errors should be correctly judged before and after reconnection.

(3) The decompression start error should be checked against the wiring diagram or schematic diagram, and carefully re-wiring.

(4) After the new motor is disconnected or reconnected to the new winding and the wiring is wrong, it shall be sent to the factory for repair.

(5) When the stator windings are connected in opposite phase, the reversed phase current is particularly large. Faults can be found and repaired according to this characteristic.

(6) Connect the "Y" type to "â–³" type or the number of turns is not enough, then the no-load current is large and it should be corrected in time.