Rare earth reduction using a novel variable magnetomotive force, flux intensified IPM machine

This paper presents a novel variable magnetomotive force, flux intensifying IPM (VFI-IPM) machine which uses only low coercive force magnets to reduce usage of rare earth metals. The VFI-IPM machine is designed with a characteristic of Ld>;Lq, which is typical for FI-IPM machines, and uses low coercive force magnets with magnetization level control. A theoretical magnet operating point analysis was conducted to investigate the design methodology. A proof-of-principle prototype machine was then designed based on these principles. Simulation results show that the VFI-IPM prototype can achieve a wide torque-speed envelope and variable torque-speed characteristics, while not requiring high coercive force magnets that would include far more expensive rare earth materials, such as dysprosium.