What happened when the motor started to trip?

22/05/2019

First check whether the motor insulation is normal. Check the motor winding with a 500V shake meter (Megohmmeter), which is qualified for 0.5 megohms and above; the motor has no problem, less than 0.5 megohms greater than 0.2 megohms, the insulation is unqualified, but it is not yet Leakage; less than 0.2 megohms is not zero, the motor has been short-circuited or there is leakage, need to continue to check to find the cause; zero insulation indicates that the motor has been grounded or short-circuited, need to continue to check to find the cause.
If there is no shaking table, take a fire wire into the motor coil, measure the outer casing with an electric pen, and the light is as bright as the live wire, indicating that the motor has been grounded or short-circuited. It is necessary to continue to check the cause; the outer casing is measured with an electric pen, although there is no fire wire, but it is obvious. Brightness, indicating that the motor has leakage, insulation is unqualified, need to continue to check to find the reason; use the electric pen to measure the casing, not bright or only weak, indicating that the motor insulation is no problem.
If the motor is qualified, it may be that the power supply has a phase loss, the power supply voltage is unbalanced (the difference is too large), the motor or the motor cable is disconnected, and the contact is poor. It needs to be checked one by one.
Check whether the motor is leaking. In the absence of the meter, the simplest is that the motor is insulated from the ground, then the winding is connected to a live wire, and the digital test pencil is used to test whether the casing has voltage, leakage or electric leakage. A short circuit between turns will not trip the leakage switch and will only cause a three-phase current imbalance. A phase-to-phase short circuit can cause the leakage switch to trip. Tripping during motor operation is often not a problem with the equipment, or there is a problem with the power supply, and the protection and personnel misoperation are not excluded. The following processing should be carried out:
(1) Immediately start the standby equipment and put it into operation. The important motor without spare equipment can be sent once. Minimize the loss and impact of motor trips on production.

(2) Measure the insulation resistance of the motor and its circuit.

(3) Check if the motor protection is working. For low-voltage motors, check whether the circuit breaker, fuses, and thermal relays are normal.

(4) Check the motor and its circuit for signs of smokeless fire, short circuit and damage.

(5) Check if the power supply is normal.

(6) Check if the mechanical part is normal, and if the motor bearing is damaged, hold the large shaft.

(7) Whether someone has misplaced the protection or accident button.