Analysis of electromagnetic torque of induction motors with two different doubly skewed rotors

摘要

Induction machines with conventional skewed rotor have lower starting torque compared with non-skewed rotor induction motors. In order to improve the electromagnetic torque, an induction motor with two different doubly skewed rotors was proposed in this paper. The fundamental electromagnetic torque and harmonic electromagnetic torque are analyzed by the virtual displacement method. Theoretical analysis shows that both doubly skewed rotor induction motor without middle ring (DSRIMWOMR) and doubly skewed rotor induction motor with middle ring (DSRIMWMR) can efficiently reduce the harmonic torque. The reduction of harmonic torque can improve the starting torque and reduce the torque ripple. The validity of the analytical method was verified by a large number of three dimensional (3-D) finite element simulations. Results of 3-D finite element analysis (FEA) indicated that both DSRIMWOMR and DSRIMWMR can improve starting torque compared with the conventional skewed rotor induction motor. Furthermore, the optimal skew width for improving the starting torque and reducing torque ripple was ascertained according to different 3-D finite element simulations.