Reasons and solutions for motor winding misconnection faults

Reasons and solutions for motor winding misconnection faults

 Incorrect winding connections can cause incomplete rotating magnetic fields, leading to difficulties in starting, unbalanced three-phase currents, high noise, and other symptoms. In severe cases, if not dealt with in a timely manner, the winding may be burned out. There are mainly the following situations: one or several coils in a certain pole phase are reversed or the head and tail are connected incorrectly; Extreme (phase) group connected in reverse; The winding of a certain phase is reversed; Multiple parallel winding branches are connected incorrectly; The connection of "△" and "Y" is incorrect.

Fault phenomenon

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

cause

Mistakenly connecting the "△" shape to the "Y" shape; During maintenance and repair, one phase of the three-phase winding is connected in reverse; Pressure reduction startup is caused by inappropriate tap position selection or internal wiring errors; When the new motor is offline, the winding connection is incorrect; The judgment of the old motor head is incorrect.

Maintenance method

(1) Ball rolling method. If the ball rotates and rolls along the inner circumferential surface of the stator, it indicates correctness; otherwise, there is a phenomenon of incorrect winding connection.

(2) Compass method. If the winding is not connected incorrectly, the polarity pointed by the compass passing through adjacent pole (phase) groups in one phase winding should be opposite, and the pole (phase) groups of adjacent different phases in a three-phase winding should also be opposite; If the polarity direction remains unchanged, it indicates that there is a polarity (phase) group connected in reverse; If the direction is uncertain, there are reverse coils in the phase group.

(3) Multi meter voltage method. According to the wiring diagram, if there is no indication on the voltmeter after two measurements, or if there is a reading on one measurement and no reading on the other, it indicates that there is a reverse connection in the winding.

(4) Common methods include dry battery method, milliampere meter residual magnetism method, and electric motor steering method.

processing method

(1) If a coil or coil group is connected in reverse, there will be a significant imbalance in the no-load current and it should be repaired at the factory.

(2) If the lead wire is incorrect, it should be correctly judged at the beginning and end before reconnecting.

(3) In case of incorrect connection during decompression start-up, refer to the wiring diagram or schematic diagram and carefully check and rewire.

(4) If the wiring of a new motor is incorrect after being taken offline or reconnected to a new winding, it should be sent to the factory for repair.

(5) When the stator winding is reversed in phase, the current of the reversed phase is particularly high. Based on this characteristic, faults can be found and repaired.

(6) If the "Y" shape is connected to a "△" shape or the number of turns is insufficient, the no-load current is high and should be corrected in a timely manner.