Design and Analysis of Outer Rotor Permanent-Magnet Vernier Machines with Overhang Structure for In-Wheel Direct-Drive Application

Dong Yu,Xiaoyan Huang,Youtong Fang,Lijian Wu

doi:10.3390/en12071238

Abstract

This paper presents a novel outer rotor permanent-magnet vernier machine (PMVM) for in-wheel direct-drive application. The overhang structures of the rotor and flux modulation pole (FMP) are introduced. The soft magnetic composite (SMC) was adopted in the FMP overhang to allow more axial flux. The 3-D finite element analysis (FEA) was carried out to prove that the proposed machine can effectively utilize the end winding space to enhance the air-gap flux density. Hence the PMVM can offer 27.3% and 14.5% higher torque density than the conventional machine with no overhang structure and the machine with only rotor overhang structure, respectively. Nevertheless, the efficiency of the proposed machine is slightly lower than the conventional ones due to the extra losses from the overhang structures.

Highlights

The vernier machine was first proposed in the form of the vernier reluctance machine without any attention at that time [1]
A novel outer rotor permanent-magnet vernier machine (PMVM) with the overhang structure of the rotor and flux modulation pole (FMP) will be proposed for the in-wheel direct-drive application
The modulation principle is based on the “magnetic gearing effect”, which means that a low-speed rotation of the permanent magnet (PM) will cause dramatic variations in flux

Summary

Introduction

The vernier machine was first proposed in the form of the vernier reluctance machine without any attention at that time [1]. The PMVM with only the rotor overhang structure received more attention recently for applications with limited space in axial direction. By utilizing the end winding space, the rotor overhang structure can enhance the air-gap flux density and the torque density. Both the analytical method and the finite element method (FEM) were carried out to analyze the effect of this structure [15,16,17,18]. A novel outer rotor PMVM with the overhang structure of the rotor and FMP will be proposed for the in-wheel direct-drive application.

Operation Principle and Machine Configurations

No-load of machine s atat600

The amplitude of the betweenM

The output waveforms of the three

Findings

Conclusions