Performance comparison of a doubly-salient motor with multi-V-shape ferrite magnets

Abstract

This paper presents the analysis of a novel doubly salient structure with concentrated tooth winding and multi-V shape ferrite magnets. Permanent Magnet Synchronous Machines (PMSM) have been universally used with rare-earth magnets or with ferrite magnets and distributed winding. The proposed topology is presented as an improvement to PMSM for high torque and low-speed applications. It has low copper losses due to its short end-winding and benefits from a low cost by virtue of its lack of rare earth materials. This paper presents two slot/pole combinations: the 18/16 and the 12/10. A 2D Finite Element Analysis is used to investigate the average torque, the power factor and the torque ripple of each structure. It is shown that high performance is achieved for both motors. However, a parametric- analysis is performed on the 18/16 motor and shows that the saliency torque cannot be improved without reducing the torque and the power factor. As for the 12/10 motor, its main drawback is its high torque ripple. The torque ripple is reduced using two techniques; a rotor step skew and the use of an asymmetric pole shape. In this paper, a combination of both methods is proposed in order to reduce specific torque harmonics. Finally a comparison of the two motors is presented in order to determine which one is more suitable for the high torque and low speed application.