Nonlinear Varying-Network Magnetic Circuit Analysis of Consequent-Pole Permanent-Magnet Motor for Electric Vehicles

Hui Wang,C C Chan,Tengbo Yang,Kwok Tong Chau,Christopher H T Lee

doi:10.3390/wevj12040254

Abstract

To conserve rare earth resources, consequent-pole permanent-magnet (CPPM) machine has been studied, which employs iron-pole to replace half PM poles. Meanwhile, to increase flux-weakening ability, hybrid excitation CPPM machine with three-dimensional (3-D) flux flow has been proposed. Considering finite element method (FEM) is time-consuming, for the analysis of the CPPM machine, this paper presents a nonlinear varying-network magnetic circuit (NVNMC), which can analytically calculate the corresponding electromagnetic performances. The key is to separate the model of CPPM machine into different elements reasonably; thus, the reluctances and magnetomotive force (MMF) sources in each element can be deduced. While taking into account magnetic saturation in the iron region, the proposed NVNMC method can accurately predict the 3-D magnetic field distribution, hence determining the corresponding back-electromotive force and electromagnetic power. Apart from providing fast calculation, this analytical method can provide physical insight on how to optimize the design parameters of this CPPM machine. Finally, the accuracy of the proposed model is verified by comparing the analytical results with the results obtained by using FEM. As a result, with so many desired attributes, this method can be employed for machine initial optimization to achieve higher power density.

Highlights

Hybrid excitation synchronous machines (HESM) incorporate both permanent magnets and field winding for field excitation [1]
According to the arrangement of PM and excitation coils, HESM can be represented as series hybrid excitation (SHE) and parallel hybrid excitation (PHE) machines [3]
It should be noted that the armature magnetic flux source (MFS) supplied by phase A, phase B, and phase C winding is represented by eight ΦA, ΦB, and ΦC modules separately, while the MFS provided by DC winding is represented by twelve ΦDC modules

Summary

Introduction

Hybrid excitation synchronous machines (HESM) incorporate both permanent magnets and field winding for field excitation [1]. By employing these two excitation field sources, the flux weakening capability and the speed range can be significantly improved [2]. For PHE machines, the excitation fluxes produced by PMs and field winding have different trajectories [4]. The risk of irreversible demagnetization of the PMs can be avoided Among those PHE machines, the consequent-pole PM (CPPM) machine possesses inherent field weakening capability [5]. In [9], the fundamental of the air-gap flux density distribution can be improved by optimizing the width of PMs. World Electr.

Method

Model Analysis

Magnetic Circuit Equations

Back-EMF