Design of Synchronous Reluctance Motor Utilizing Dual-Phase Material for Traction Applications

Abstract

While interior permanent magnet (IPM) machines have been considered the state-of-the art for traction motors, synchronous reluctance (SynRel) motors with advanced materials can provide a competitive alternative. IPM machines typically utilize neodymium iron boron permanent magnets, which pose an issue in terms of price, sustainability, demagnetization at higher operating temperatures, and uncontrolled generation. On the other hand, SynRel machines do not contain any magnets and are free from these issues. However, the absence of magnets as well the presence of bridges and center post limit the flux-weakening capability of a SynRel machine and limit the achievable constant power speed ratio for a given power converter rating. In this paper, a new material referred to as the dual-phase magnetic material will be evaluated for SynRel designs. This material allows for nonmagnetic regions to be selectively introduced in the bridge and post regions, thereby eliminating one of the key limitations of the SynRel designs in terms of torque density and flux weakening. This paper will focus on advanced SynRel designs utilizing dual-phase material targeting traction applications. The paper will provide a detailed comparison between a dual-phase SynRel design, a conventional SynRel design, and a spoke PM design with rare-earth-free magnets. It will highlight the key tradeoffs in terms of power density, efficiency, and flux-weakening capability.