FEM Analysis of Auxiliary Poles of IPM Synchronous Machine With "Flux Concentration Function"

Abstract

The interior permanent magnet (IPM) machine, which enjoys advantages such as high efficiency and torque, is widely used not only in home application like air conditioners but also in electric vehicles. Its leakage flux is bigger than surface mounted permanent magnet (SPM), however, because the magnetization direction of permanent magnet is plumb to axes of air gap flux and far away from air gap. In order to reduce leakage flux and improve air gap flux density, we may add auxiliary poles in rotor structure. This paper adopts the vector magnetism potential to calculate machines field, and aim at model of 4 kinds, compare the relation between leakage flux of permanent magnet beside the shaft and equivalent air gap when auxiliary poles are existent and non-existent, respectively. Then, discusses the influence of auxiliary poles in different positions on air gap flux density when pole pairs are different, point out placement position of auxiliary poles and optimizes thickness of Rare Earth magnet in that position. At same time, the paper analyzes the influence of the thickness of auxiliary poles on the air gap flux density as pole pairs vary.