A High-Torque-Density Permanent-Magnet Free Motor for in-Wheel Electric Vehicle Application

Abstract

A motor for in-wheel electric vehicle (EV) requires high efficiency and specific torque. In view of this, permanent-magnet brushless dc (PM BLDC) motor is most commonly employed for this application. However, due to the increasing cost of PMs, machines that do not use PMs are attracting interest. Switched reluctance motor (SRM), with its simple and robust construction, along with fault tolerant operation, is a viable option for in-wheel EV application. However, the SRM has low specific torque as compared with BLDC. Therefore, design improvements are required to make SRM a viable alternative to BLDC motor. In this paper, a new 12/26 pole SRM with high specific torque is proposed for in-wheel EV application. This machine has segmented-rotor-type construction. Also, concentrated-winding arrangement is used, ensuring low end-winding volume and copper loss. The developed machine also has high efficiency. In order to verify the design, the prototype of the machine is fabricated, and experimental results are presented.