Comparison of alternative skew-effect parameters of cage induction motors

Abstract

A comparison is made of the validity and practical utility of five different methods, used to varying extents in practice, of accounting for the effect of rotor skew in predicting the performance characteristics of cage induction motors. It is shown that, of the two methods which are theoretically valid, the one commonly used is the less practical for computing the combined effect of mutual and leakage fluxes under conditions of magnetic saturation. It should be superseded by the other equally valid method, which is shown here to deal more directly with the internal electromagnetic conditions of the motor. With regard to the remaining three methods, it is demonstrated that although all are fundamentally invalid, one of them has practical utility as a simple expedient for inherently taking a preliminary account of the stray load and increased magnetic-saturation effects experienced with skewed cage induction motors.