Analysis of Even Order MMF Harmonics in Squirrel Cage Induction Motors

Even harmonics of mmf are produced whenever the excitations on the separate poles of a winding are unequal as in some starting connections used in single phase motors or in certain consequent pole windings. The analytical methods developed in this paper are applicable to any three-winding squirrel cage induction machine with arbitrary mmf distribution in all three windings. A center-tapped main winding single phase motor is used as an example and the reduction in performance caused by even harmonics is shown both analytically and experimentally. The theory is applicable to both steady state and dynamic performance and illustrative results for the transient performance of the sample motor are included. Application of the method to three phase machines is discussed.