Optimization of an 80-kW Segmental Rotor Switched Reluctance Machine for Automotive Traction

There is significant interest in the development of switched reluctance machines (SRMs) for use in automotive traction applications. This has been driven by their low cost compared with rare earth permanent-magnet-based motors, driven by the high cost of rare earth permanent magnets, coupled with their potential for competitive torque densities. This paper describes the development of a variant of the SRM, utilizing a segmental rotor construction, which has previously been demonstrated to provide the potential for significant improvement in torque densities compared with SRMs with a conventional toothed rotor construction. This paper describes a strategy that has been developed to optimize the Segmental Rotor SRM to maximize efficiency with the aim of achieving performance equivalent to that of the 80-kW interior permanent-magnet machine utilized in Nissan's LEAF electric vehicle. Optimization applies a combination of static and dynamic analyses in order to achieve a full and computationally efficient assessment of motor performance across different regions of the torque speed envelope. Test results from a prototype motor are also presented.