Influences of Winding MMF Harmonics on Torque Characteristics in Surface-Mounted Permanent Magnet Vernier Machines

Daekyu Jang,Junghwan Chang

doi:10.3390/en10040580

Abstract

This paper presents the influences of winding magneto-motive force (MMF) harmonics on the torque characteristics in surface-mounted permanent magnet vernier (SPMV) machines. Based on the magnetic gearing effects, the armature magnetic field of the SPMV machines is modulated by flux modulation poles (FMPs). In the modulated magnetic field, a working harmonic which corresponds to the number of the rotor pole pairs generates torque. Unlike regular PM machines, the winding MMF harmonics in the SPMV machines can produce the working harmonic by adjusting the FMP shapes. In order to investigate the effects of the winding MMF harmonics, the operating principle of the SPMV machines is elaborated by an analytical method using the winding MMF distribution and air-gap permeance function. After that, the design method of the FMP shapes that can improve the output torque by using the winding MMF harmonics is proposed. For the SPMV machine having 6 slots and 24 FMPs, the effects of the winding MMF harmonics and the validity of the proposed design method are confirmed by the finite element analysis method. It is shown that the proposed design method can improve the performances of the SPMV machine in terms of the torque density, induced electromagnetic force, and efficiency.

Highlights

In many industrial applications which require high torque capability, permanent magnet vernier (PMV) machines have attracted much attention due to their high torque density and high efficiency [1,2,3,4,5].In the PMV machines, the low spatial harmonic of the winding magneto-motive force (MMF)distribution in the air-gap is modulated into the higher spatial harmonic by flux modulation poles (FMPs), which are formed on the stator
This paper presents the influences of the winding MMF harmonics on the output torque in the surface-mounted PMV (SPMV) machine
The operating principle of the SPMV machine is elaborated by using the analytical equation which is derived from the winding MMF distribution and the air-gap permeance function

Summary

Introduction

In many industrial applications which require high torque capability, permanent magnet vernier (PMV) machines have attracted much attention due to their high torque density and high efficiency [1,2,3,4,5].In the PMV machines, the low spatial harmonic of the winding magneto-motive force (MMF)distribution in the air-gap is modulated into the higher spatial harmonic by flux modulation poles (FMPs), which are formed on the stator. The resulting higher spatial harmonic generates torque by interacting with the rotor PM magnetic field of the same spatial order. Based on the principle of the magnetic field modulation, many topologies of the PMV machines have been investigated in order to improve their torque density and power factor [6,7,8,9,10,11]. In surface-mounted PM (SPM) machines, due to the stator slotting, the air-gap permeance function includes the harmonic of the spatial order corresponding to the number of the slots [12]. The effect of the stator slotting cannot improve the magnitude of the generated torque in the SPM machines. The surface-mounted PMV (SPMV) machines employ the harmonics of the air-gap permeance function for their high torque capability. In the SPMV machines, the air-gap permeance function is determined

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Conclusion