Design considerations of switched reluctance motors with bipolar excitation for low torque ripple applications

Switched reluctance motors (SRMs) have been applied to many applications over the past decades due to their simple structure, low cost, and robustness. The primary disadvantage of SRMs is the relatively high torque ripple. In this paper, the machine design is considered under a two-mode bipolar excitation to achieve the optimum performance of a mutually coupled switched reluctance motor (MCSRM) for low torque ripple applications. Geometrical design equations and practical challenges are investigated. In addition, a six-slot, ten-pole (6/10) SRM with a six-phase winding configuration under the two-mode bipolar excitation is optimized by solving a multiobjective optimization problem using a quasi-Newton optimization method with considering the tradeoff between the torque ripple reduction and the efficiency improvement. The combination of the two-mode excitation scheme and corresponding optimal machine design effectively reduces the torque ripple without sacrificing the average torque produced by the MCSRM. The design considerations are verified by the finite element method (FEM)-based simulation results.