The research of auxiliary poles of IPM synchronous machine using FEM analysis

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), 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, 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, and obtained: 1) The reasonable introduction of the auxiliary poles can reduce the leakage flux of the main poles and increase its air gap flux density in IPM machine; 2) As to main poles, the auxiliary poles may be placed in three different positions, among which positions in Models (b) and (c) are relatively reasonable, the amount of the permanent magnet material is moderate and the contribution to the air gap flux is greater; 3) The rare earth magnet thickness of the auxiliary poles has a relatively reasonable value, which is relative to the pole pairs of the machine.