1. When the stator winding is short-circuited, you may see smoke from the motor.
2. When the motor is severely overloaded or running under phase loss, the speed will slow down and there will be a heavier “humming” sound.
3. When the motor runs normally, but suddenly stops, you will see sparks from the loose wiring; the fuse is blown or a component is stuck.
4. If the motor vibrates violently, it may be that the transmission device is jammed, the motor is not properly fixed, and the foot bolts are loose.
5. If there are discoloration, burn marks and smoke traces at the contact points and connections in the motor, it means that there may be local overheating, poor contact at the conductor connection, or burned windings.