I- Introduction

II- SRM Analytical Torque Model

III- Comparison Study of Six-Phase Topologies

IV- Copper Loss for Multiphase Machine

V- Experimental Validation

VI- CONCLUSION

References

INTRODUCTION

SWITCHED reluctance machines (SRMs) have excellent features such as simple and robust structures, high manufacturability, good fault-tolerant capability, and also low cost. In addition, without permanent magnets or field windings on the rotor, they are particularly suitable for harsh environmental operations such as high speed and high temperature. Due to these significant advantages, SRMs have attracted increasing interest in electric vehicles, aerospace, and other safety-critical applications [1], [2]. However, the doubly salient structure together with the special rectangular wave current supply causes high torque ripple, high vibrations, and acoustic noise compared with other types of machines. Therefore, in past decades, the torque ripple reduction is one of the most popular research topics for SRMs. This can be achieved from two aspects: machine design [3]–[۵] and also advanced control [6], [7]. One effective and simple way to reduce the torque ripple is to increase the phase number. This method can be applicable not only to SRMs but also to synchronous (reluctance) machines and induction machines. Multiphase machines provide additional benefits apart from the torque ripple reduction because the machines with higher phase numbers (m > 3) can also have higher torque density and better faulttolerant capability compared with conventional three-phase machines [8]. In addition, different winding configurations for multiphase machines can be selected to achieve even better torque performance [9], [10]. The conventional SRMs, with three-phase or multiphase, are supplied with rectangular wave current. However, recent studies have shown that they can be supplied with sine wave currents as well [11], [12]. It has been found that the sine wave excitations can bring benefit to the radial force reduction for SRMs, which are the primary source of vibrations and acoustic noise. One of the other advantages of sine wave excitation is that the standard three-phase voltage source inverter as that used in synchronous (reluctance) machines or induction machines can be employed, which can help reduce the system cost. It also provides a more flexible control strategy for SRMs to improve the torque performance. However, it is worth noting that the SRMs with sine wave current supply are actually doubly salient synchronous reluctance machines (DS-SRMs) [13]–[۱۵].