1) Phase deficiency operation of low-voltage motor
Three phase winding one or two phases all become black brown, generally due to the lack of phase operation. The cause of phase loss generally occurs in the power supply system, and very few occur in the motor (u-turn or lead breakage). In this case, we should first check whether the lead is turned around or the lead is burned, otherwise it belongs to the power supply line problem, and the motor has nothing to do.
2) When all the three-phase windings of the motor turn black, it indicates that the motor has been overloaded (running over current) for a long time, which does not belong to the manufacturing quality problem of the motor.
3) The insulation color of the integral winding does not change, and the local inter-turn or short circuit to the ground is generally a product problem.
To solve the problem of burning the winding of this kind of motor, it is generally necessary to replace the winding and replace the damaged parts.
Precautions for maintenance: the insulation resistance of the winding should be tested before starting the motor again after each shutdown; When the insulation resistance value of the motor is relatively low after long-term placing, or there is an obvious phenomenon of damp, the motor should be treated accordingly, and the insulation resistance value should be restored to normal before starting the motor; If the motor is hastily started when the insulation resistance is known to be relatively low, it will cause the winding breaking pressure problem.