(1) three-phase voltage unbalance;
(2) the motor branch-poor welding or contact is not good;
(3) motor winding short circuit or to ground, short circuit between phases;
(4) wiring errors.
Why can not be used with the 50Hz power 60Hz motor?
Design-time General Motors silicon steel sheet magnetization curves of saturated, when supply voltage is constant, the lower frequency will increase the flux and excitation
Flow, resulting in increased motor current, increasing consumption of copper, eventually leading to the motor temperature rise, which may also be due to overheating of the coil motor.