Transient Overspeeding of Induction Motors

A transient swing above synchronous speed has been observed when a certain standard squirrel cage induction motor was started without load. This paper presents an explanation of the phenomenon based on the frequency modulation of the power supply caused by the rapid variation of the power taken from the line. Mathematical relations are developed and applied to the operating conditions of this motor. The agreement of the mathematical and test curves indicates that the explanation is basically correct although some secondary effects, not considered, may be present.