Self-excited wound rotor synchronous motors for electric vehicles: Techniques and multiphase winding design strategies

Self-excited wound rotor synchronous motors (WRSM) have emerged as a promising substitute to permanent magnet (PM) motors in electric vehicles (EVs), offering significant cost reductions and alleviating concerns over PM material availability. Additionally, WRSMs demonstrate strong performance across varying speed ranges and eliminate the necessity for frequent maintenance, thanks to the absence of motor brushes. This paper provides a comprehensive survey of the various self-excitation techniques documented in the literature, with a particular focus on the recently developed multi-phase-based method that decouple the control of armature and field windings, enhancing both efficiency and flexibility. The study further proposes a strategic approach for designing winding layouts for both the rotor and stator in multiphase machines. Finally, the paper evaluates the performance of the most prevalent five-phase and six-phase slot/pole combinations in the EV traction field, offering valuable insights for optimizing WRSM design and application.