Vibration Analysis of an Induction Motor under Electromagnetic Force

Abstract

Three-phase induction motor causes an unstable vibration because of electromagnetic force. In this paper, a criterion for unstable vibration was introduced. To confirm this criterion, numerical integration was carried out and the results showed a good agreement with the unstable region obtained by the criterion. This criterion gives us the complete story about the stability for the case when the parameters e.g., phase current, air gap length etc. are changed. It was cleared that the natural frequency changes owing to the variation of the phase current, and that the unstable vibration occurs when the frequency of power supply and the natural frequency (changed by current) are nearly the same. And it was also showed that the parameters can be classified into the categories whether they have influences on the stability or not.