Direct modeling of the starting process of skewed rotor induction motors using a multi-slice technique

Both the starting current and the starting torque of induction motors canno t be evaluated and measured accurately and readily. In particular, the geom etrical features of the skewed rotor bars are very difficult to study if a general 2-D finite element method is used. This paper presents an approach in using a multi-slice, time stepping 2-D eddy-current finite element metho d to study the starting processes of skewed rotor induction machines. The f ields of the multi-slices are being solved en bloc simultaneously, and thus the eddy current effects can be taken into account directly. New forms of the governing equations for the multi-slice model are derived so as to allo w the meshes of the multi-slices to be taken as one 2-D mesh. The resultant algorithm is then very similar to that of general 2-D problems. Special ti me stepping techniques for studying the starting process of motors are also presented. The performances of motors with skewed and non-skewed rotor are shown. It was found that the simulation results correlated very well with test data.