A: 1) The mechanical load is too heavy, its main feature is that the motor is hot, touching the motor shell by hand, which is obviously hot; it can also read the running current from the inverter display screen, compare with the rated current of the motor, and judge the overload situation.

2) Three phase voltage unbalance
The operation current of a certain phase is too large, resulting in overload trip. Its characteristic is that the motor heating is unbalanced, and it may not be found when reading the running current from the display screen (because many inverter displays only one phase current); the effective method is to measure the three-phase output voltage of the inverter with a voltmeter, so as to judge whether the inverter is lack of phase or voltage imbalance.

3) Misoperation
The internal current detection part of the inverter breaks down, and the detected current signal is too large, resulting in overload trip