Unstable Electrical Vibration of an Induction Motor.

The rotor of a three-phase induction motor occasionally produces an unstable electrical vibration of the power source frequency. In this paper, we studied the electromagnetic exciting force of two times the power source frequency caused by imbalance of the magnetomotive force on the stator core. The unstable electrical vibration induced by the exciting force was investigated by numerical calculation and experiment. The criterion for unstable electrical vibration was analyzed.