Switched Reluctance Machines with higher rotor poles than stator poles for improved output torque characteristics

Abstract

Switched reluctance motor (SRM) drives have gained considerable popularity for automotive, defense and aerospace applications which desire ruggedness, high speed capability, and fault tolerance. In spite of significant progress in the development of advanced control strategies over the past two decades, high levels of torque pulsation and acoustic noise in SRM drives still present a major shortcoming. This paper discusses the improvement of torque characteristics of an SRM by including a higher number of rotor poles than stator poles. A numerical relationship called pole design (PD) formula is used to generate new configurations of SRMs. Particularly, this paper focuses on the enhancement of design and development of a SRM, whether operated as a motor, generator, or both, based on this novel formula and investigates such design for low cost manufacturing for high volume applications, torque ripple, torque density, and efficiency. For the verification of the claims presented, a prototype SRM designed using PD formula with 6 stator poles and 10 rotor poles (6/10 configuration) is evaluated and compared to a conventional three-phase 6/4 configuration with similar constraints. Results obtained from simulations using finite element analysis (FEA) and experimental measurements have been presented comparing the output torque for each topology. Comparisons have been made in terms of torque ripple and average torque values for two specific conduction angles.