Principle of Torque Ripple Reduction in Synchronous Reluctance Motors With Shifted Asymmetrical Poles

Abstract

In this paper, the principle of torque ripple reduction in synchronous reluctance motors (SynRMs) with shifted asymmetrical poles is revealed. The key of this principle is that the asymmetrical poles and shifted pole pairs are combined to reduce the torque ripple while their functions are different. The adjacent poles are designed as asymmetrical to suppress the second-order harmonic of torque ripple. Nevertheless, two asymmetrical poles are selected as a repeating unit, and then, the half of repeating units of the SynRM are shifted to eliminate the main order harmonic of torque ripple. In order to obtain the principle of torque ripple reduction, a simple five-phase SynRM with salient poles is proposed and the analytical model is built. Then, the asymmetrical angle and shifted angle to reduce the second-order and main order harmonics of torque ripple are revealed by the analytical method, respectively. Furthermore, the revealed principle can be extended into SynRMs with multilayer flux barriers or other combinations of stator slots and rotor poles. In order to evaluate the revealed torque ripple reduction principle, a prototype with simple salient poles is manufactured for experiments. Through the experimental test, it is verified that the revealed principle is feasible and effective.