Adjustment of step size for time stepping finite element analysis on skewed rotor induction motors fed by SPWM source

SPWM techniques have been widely applied in the control of electrical machines. One of the problems of such inverter driven motors is the detrimental effect of a large amount of high-order harmonics. A precise estimation of the high-order harmonic field is of paramount importance for a thorough study of the performance of the motor when it is fed from SPWM. In this paper a 2-D multi-slice time stepping finite element method is proposed to model SPWM driven induction motors so that the high-order harmonic field can be directly included in the solution. To deal with the choice of the step size during the time stepping process when the motor is fed from a SPWM source, a method to adjust the step size according to the turn-on/turn-off time of the switches is presented. The method significantly reduces the integrating time as well as the error in the time stepping process