Cylindrical rotor design for acoustic noise and windage loss reduction in switched reluctance motor for HEV applications

A Switched Reluctance Motor (SRM) is one of the candidates of rare-earth-free-motors for hybrid electric vehicle (HEV). An SRM has been developed with exact IPMSM dimensions with competitive maximum torque, operating area, and maximum efficiency. However, considered windage loss of around 1.3 kW is resulted by the salient poles of the SRM at the maximum rotational speed. In addition, considerable acoustic noise is caused by the salient poles. In this paper, a simple design of a cylindrical outer shape rotor is proposed and a comparison to the conventional rotor is carried out. It is found that the efficiency is improved thanks to the windage loss reduction. It is also found that the acoustic noise is significantly reduced.