Reduced Dysprosium permanent magnets and their applications in electric vehicle traction motors

As a promising solution to the energy and environment concerns in today's world, electric vehicles (EVs) are receiving increasing interest. An EV traction motor requires a wide torque-speed range, high power density and high energy efficiency. Hence, permanent magnet (PM) brushless machines are an attractive candidate. Nd2Fe14B magnet is one of the key materials for high performance PM machines, thanks to its high energy product. However, the volatile supply chain of heavy rare earth elements has made the magnets subject to massive price fluctuation and extremely high cost. This is especially the case for the Dysprosium (Dy), whose price is almost as 6 times high as the Neodymium (Nd). Since the operating temperatures of traction motors can reach 150°C at which the coercivity (Hc) of pure Nd2Fe14B magnets is too low, Dy plays an important role in the Nd2Fe14B magnet as small addition of Dy substitutes the Nd to form (Dy, Nd)2Fe14B which has a higher anisotropy field than Nd2Fe14B, thus can significantly increase the Hc and elevate the temperature performance