What are the causes of motor phase loss?

The reason for the phase loss of the motor is because the power supply line does not supply the three-phase voltage to the motor at the same time, generally the contactor or circuit breaker and then the line is broken;

For three-phase asynchronous motors, the normal operation should be that the three-phase symmetrical AC current is passed into the three-phase symmetrical stator winding to generate a circular rotating magnetic field, when the three-phase current is missing one phase. The motor will have abnormal operation, and the main reasons for the phase loss failure of the motor are as follows.

1. The three-phase power supply with phase loss of power supply is before the AC motor is turned on. The power supply has lost one or two phases (the power supply has been in trouble, and the one-phase melt in the three-phase fuse has been blown out), which can cause the motor to fail to start or start to not operate normally.

2. The terminal post in the motor junction box is loose, and the one-phase winding of the three-phase winding of the motor stator is broken, which causes the phase loss of the three-phase motor operation.

3. The connector is virtual or the connector in the power supply line is disconnected, which may also be broken by external force, which will also make the motor phase missing.

4. The contactors and relays in the phase loss control loop caused by the control loop may have a certain degree of oxidation on the contacts after long-term use. Cause poor contact, or wear of the component action mechanism for a long time. These electrical components, when subjected to the motor starting current (generally 5 to 7 times the rated current) impact, or by electromechanical equipment vibration or motion mechanism jamming failure and other wrong actions, the stator winding will be out of phase.

5. After a considerable period of operation of the insulation aging motor, the insulation of the stator winding may age (the ambient temperature of the motor running for a long time is too high). When the power supply voltage is high or the load is too large (causing a short circuit between phases or turns of the motor stator winding), it will also cause the motor stator winding to break one or more phases.