1. The use of PEN measurement shell, although there is no FireWire bright, but there is a clear brightness, indicating that the motor has leakage, insulation unqualified, need to continue to check to find the reason; The electric pen measure the shell, not bright or only weak, indicating that the electrical insulation is no problem.
2. If the electrical insulation qualified, may be the power supply has a phase, the power supply voltage imbalance (the difference is too large), motor or motor line has broken, bad contact and other problems, need one by one troubleshooting.
3. Check whether the electrical leakage, there is no instrument, the simple is, the motor and the Earth insulation, and then the winding connected to a line of fire, with the digital Tape test chassis have no voltage, there, leakage. Turn short-circuit will not cause leakage switch tripping, will only cause three-phase current imbalance. Short circuit will cause leakage switch tripping.
The above is the possibility of tripping the motor, for the above reasons to find the problem is very easy to solve the problem, of course, if you encounter problems can be consulted related personnel to answer or repair.