A three-phase asynchronous motor does not start after power, only hums.

    Analysis and examination: three-phase asynchronous motor is powered only hum but not turn the phenomenon, indicating that the power supply is off not one phase melt-off is the motor winding phase circuit, immediately turn off the power and check. The detection result is contact with a poor contact.

    Repair methods: by adjusting and tuning contactor when closing test in case of no electricity drop-down, three-phase moving contact opening and closing the same tight contact; energized Checking the contact is good contact, motor starting soon, nor hum .