Effect of Armature Reaction on Asymmetric PM Eddy Current Loss and Temperature Distributions of SPMSMs Accounting for Slot/pole Number Combinations

This paper utilizes the harmonic restoration method to evaluate and quantify the contributions of individual armature reaction spatial harmonics to permanent magnet (PM) eddy current loss and temperature distributions for 12-slot surface-mounted PM synchronous machines (SPMSMs) with different pole numbers. It is shown that for each of SPMSMs with different pole number, there is one dominant spatial harmonic contributing to the majority of PM loss, and its interaction with the PM field causes asymmetric PM loss distribution. Besides, with the pole numbers increasing from 8 to 22, the maximum loss density in one PM pole moves from the circumferential centre to the edge. Consequently, the resultant PM local hotspot temperature has the same tendency, which has been verified by the 3-D thermal finite element method and experiments.

I. Introduction

Due to high efficiency and high torque density, permanent magnet (PM) synchronous machines (PMSMs) have been widely employed in domestic appliances, servo drives, electric vehicles, wind power generation, etc. [1]. Surface-mounted PMSM (SPMSM) is one of the most preferred choices due to its simple structure, where the PMs are mounted on the surface of the rotor and adjacent to the airgap.