Torque Ripple Reduction of a Salient-Pole Permanent Magnet Synchronous Machine With an Advanced Step-Skewed Rotor Design

Abstract

In this paper, a salient-pole permanent magnet synchronous machine (SPPMSM) is introduced to high-speed trains, taking advantage of its high utilization of the reluctance torque from the unbalanced reactance. Torque characteristics, such as average torque and torque ripple, are rather important and should be carefully concerned during the optimal design of the SPPMSM. Both the eccentric air-gap and the advanced step-skewed rotor (ASSR) design are developed and implemented to reduce the torque ripple for comfort and safety issues. Compared to the conventional step-skewed rotor (CSSR), the ASSR takes advantage of the high utilization of permanent magnets (PMs), which are axial continuous assembled, and the easier manufacture with a single rotor lamination model, which is asymmetrically designed with pole shoes skewed by individual skewing angles. No skewing arrangement is applied to the rotor yoke and the PM chambers. The impacts of the eccentric air-gap and the ASSR on the torque characteristics are comprehensively investigated by finite element analysis. The results show that the proposed technique can significantly reduce the torque ripple with a slight expense of the average torque. Based on the optimal eccentric design, experiments of the SPPMSM with the non-skewed rotor, CSSR, and ASSR under various conditions are carried out to validate the estimated results.

Keywords

• Eccentricity design
• permanent magnet synchronous machine
• step-skewed rotor
• torque ripple