Technology trends,challenges,and opportunities of reduced-rare-earth PM motor for modern electric vehicles

Nowadays,with increasing concerns about environmental pollution and energy crisis electric vehicles are rapidly developing owing to their significant environmental-friendly benefits.To meet the diverse driving requirements of electric vehicles,the PM motors with high-performance rare-earth PMs have been widely employed in electric vehicle powertrains,which shows the performance merits of high power density and high efficiency.Yet,rare-earth PMs,as non-renewable strategic resources,usually suffer from unstable supply and fluctuation prices,which increases the potential risks of further large-scale application of rare-earth PM motors.And this also poses a negative factor for the long-term sustainable development of electric vehicles or other applications that rely heavily on rareearth PM materials.Under this background,a type of less-rare-earth PM motors,which aims to effectively alleviate the dependence of high-performance PM motors on rare-earth PMs,has recently drawn increasing attention from experts and scholars.It implies that the investigation and development of less-rare-earth PM motors without compromising performances is becoming a new and hot research direction in the motor field.This paper reviews the existing main alternatives for less-rare-earth PM motors.Based on the dominated torque component,the less-rareearth PM motors are divided into two types,which are the less-rare-earth PM-dominated motor and less-rare-earth PM-assisted motor.The operation principle,design considerations and restrictions of each type of less-rare-earth PM motor is sequentially discussed.Finally,combined with the potential electric vehicle application,the key problems of less-rare-earth PM motor are summarized and the corresponding technological means are prospected.