Overview of Development Trends of Rare-Earth-Less Machines for Electric Vehicle Applications

In recent years, there has been rapid development in the field of electric vehicles (EVs), with a steady increase in market share. Permanent magnet synchronous machines (PMSMs), particularly those employing rare-earth PMs, have emerged as the predominant choice for propulsion systems of EVs, owing to their compact size, high power density, and high efficiency. However, the persistently high and fluctuating prices of rare-earth PMs lead to the overall high cost of machines. To mitigate the cost of drive motors, this paper explores the potential of three types of rare-earth less machines: PM-assisted synchronous reluctance machines (PMaSynRMs), hybrid PM assisted synchronous reluctance machines (HPMaSynRMs), and hybrid excitation machines (HEMs). The current development, advantages, and respective challenges of these three types of machines are discussed from various perspectives. In summary, the current power density levels of these three types of machines have not yet reached those of rare-earth PMSMs. However, due to their significant cost advantage in PMs, they are likely to be suitable for new energy vehicles where the power density requirements are not as stringent.