Simplified Equations According to Skew for Pole-Pieces of 1 kW-Class Dual-Rotor Permanent Magnet Synchronous Motor for Railway Vehicles

Abstract

This paper presents the simplified equation of skew for pole-pieces of dual-rotor permanent magnet synchronous motor combined with magnetic gear (DR-PMSM) for railway vehicles. Generally, in the case of a permanent magnet synchronous motor (PMSM), the skew is applied to the rotor to reduce the cogging torque. In the case of DR-PMSM, it is structurally or productively more advantageous to apply skew to the pole-pieces (outer rotor) than the inner rotor. However, this method is mathematically complicated and the study on it is insufficient compared to the conventional PMSM. Therefore, this paper introduces simplified equations of optimal pole-pieces skew and the peak to peak of cogging torque according to the skew angle.