Review and Future Developments of Wound Field Synchronous Motors in Automotive

Electric motors are increasingly spreading in the automotive sector, following the progressive electrification of transportation aimed to reduce CO2 emissions and increase sustainability. Most of the employed motors are permanent magnets (PM) based and these materials are subjected to price fluctuations. In addition, they are not the key for sustainability, especially when referring to rare earth materials. An alternative to the classic PM motors is the wound field synchronous machine (WFSM) which, thanks to the absence of magnets, represents an inherent more sustainable solution. In addition, this machine presents higher controllability and fault tolerance compared to their PM counterpart, which on the other hand features higher torque density and efficiency values. While WFSMs have been widely adopted and studied as power generators in grid-connected and isolated power plants, their use as traction motors is limited and under investigation. This paper aims to resume the state of the art of WFSMs and to analyze the challenges of its employability in the automotive field. Possible future developments, contextualized considering the authors' vision, will be also discussed.