Causes of motor phase failure

The reason for the motor phase missing is that the power line does not supply the three-phase voltage to the motor at the same time. Usually there is a line disconnect. The phenomenon is that if the motor can rotate without load, it will heat up and buzz instantly, and the rotation will be weak. It instantly buzzes and overheats under heavy load, and if the power is not cut off in time, the motor will be burnt out.

For the three-phase asynchronous, the normal operation should be that the three-phase symmetrical alternating current passes through the winding of the three-phase symmetrical stator to generate a circular rotating magnetic field. When the three-phase current loses a phase. The motor will appear abnormal operation phenomenon, and the reasons for the motor phase loss fault mainly include the following situations.

1. Phase loss

Before three-phase power is connected to the AC motor. Therepower supply has lost one or two phases (there was a problem with the power supply and a phase of the three-phase fuse has blown), which may prevent the motor from starting or start abnormally.

2. The control circuit causes phase loss

The control circuit contactor, after long-term use, may have some degree of oxidation on the contacts . Cause poor contact or long-term wear of the component action mechanism. These, when subjected to the impact of motor starting current (generally 5 to 7 times the rated current), or vibration of electromechanical equipment or malfunction of travel mechanism, etc., cause phase loss of the stator winding. .

3. Terminal in motor junction box is loose

One of the three-phase motor stator windings is disconnected. As a result, the motor is out of phase.

4.Virtual connection or disconnection of the connection head

If the connection head in the power line has a virtual connection or can be broken by an external force, it will also cause the motor to lose phase.

5. Insulation aging

After prolonged operation of the motor, the insulation of the stator winding may age (the motor ambient temperature is too high for a long period.The supply voltage is too high or the load When it is too large), it will cause a phase-to-phase or inter-turn short circuit of the motor stator winding, and one or more phases of the motor stator winding will also be disconnected.

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