What does it mean when a three-phase motor is out of phase

When a three-phase motor lacks phase, what will be the impact on the motor? What's going on? What's the harm.

We often use three-phase asynchronous motors in industrial and agricultural production, and three-phase asynchronous motors have various faults, among which the three-phase asynchronous motor is a common fault for the motor to run out of phase. Let's talk about what phenomenon the motor will produce when there is phase loss, and what are the reasons for phase loss, and how to deal with it, I hope it will help you.

1. What are the reasons for the lack of phase in the motor?

The reason for the lack of phase of the motor is that 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 three symmetrical alternating current currents are fed into the three symmetrical stator windings to produce 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 lack of phase failure of the motor are as follows.

1. The power supply is out of phase before the AC motor is turned on. The power supply is already missing one or two phases (there is already a problem with the power supply, and the melt in one phase of the three-phase fuse is blown out), which can cause the motor to not start or start to operate normally.

2. The binding post in the junction box of the motor is loosened and the one-phase winding in the three-phase winding of the motor stator is broken, which causes the three-phase motor to run out of phase.

3. The connection head is falsely connected or the connection head in the power supply line is falsely connected, which may also be broken by external force, which will also make the motor lose phase.

4. The contactor and relay in the phase loss control loop caused by the control loop may oxidize to a certain extent on the contact after long-term use. Poor contact or wear of the component operating mechanism for a long time. When these electrical components are impacted by the starting current of the motor (generally 5 to 7 times the rated current), or when they are vibrated by the electromechanical equipment or the movement mechanism is stuck and malfunctioning, the stator winding will lose phase.

5. After a considerable period of operation, the insulation of the stator winding may be aged (the ambient temperature of the motor is too high for a long time). When the power supply voltage is too high or the load is too large (resulting in a short circuit between phases or turns of the stator windings of the motor), it will also cause the stator winding of the motor to be disconnected by one or more phases.

Second, the phenomenon of phase loss operation of the motor:

1. The speed of the motor decreases;

2. The temperature of the motor body rises;

3. The phase without the ammeter is disconnected, and the motor current increases; When the phase on which the ammeter is installed, the wire is disconnected, and the ammeter indication is zero.

4. There is a strong "buzzing" sound when starting but it cannot be started, or it cannot reach the normal speed after starting.

5. The vibration of the motor increases;

3. Hazards and treatment methods:

When the above phenomenon is found, it should be stopped immediately and it is strictly forbidden to start, otherwise the motor will be burned.

After the motor is burned out of phase, the intuitive fault characteristic of the winding is the regular winding burn marks, and the degree of burnout is not too much. In turn-to-turn, phase-to-phase or ground faults, the fault point location is burned out particularly severely, and the fault that spreads out is relatively light, which is a characteristic of phase loss fault that is different from other faults.