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

This paper describes a new Dy grain boundary diffusion process for sintered Nd₂Fe₁₄B magnets for applications in EV traction machines. The new process results in a 75% reduction in Dy consumption normally required by conventional Nd₂Fe₁₄B magnets for the equivalent performance, thus quite diminishes the dependence on the high-cost and volatile supply of rare earth element. An interior permanent magnet machine (IPM) with 18 slots and 8 poles is also designed and built with the low-Dy content magnets for a small sized electric vehicle. With the help of the new magnets, the prototype machine has reached very high energy efficiency over a wide torque-speed range in the test, while the magnet material cost is significantly reduced .