Suppression of Torque Ripple for Consequent Pole PM Machine by Asymmetric Pole Shaping Method

Abstract

Consequent pole (CP) permanent magnet (PM) machines have attracted considerable interest as a means of reducing machine cost through a marked reduction in the volume of permanent magnet required to meet a particular torque specification. However, the presence of a large torque ripple that can result from the CPPM structure can hinder their adoption in some applications, especially for the dominant third order torque ripple. Although several design-specific modifications have been proposed to ameliorate torque ripple, arguably the generalized principles underpinning this behavior have not been fully established. In this paper, it will be illustrated that an aggregation of the fluctuations in inductance, back EMF and cogging torque contributes to increased torque ripple. Meanwhile, an asymmetric pole shaping method is proposed to reduce the torque ripple, taking the dominant third order torque ripple as example. Simulated results of the 12-slot/8-pole prototypes show that compared to symmetrical pole shaping model and the plain pole model, the proposed asymmetric shaping method is effective in reducing torque ripple.