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

Takashi Kato, Natee Limsuwan, Chen Yen Yu, Kan Akatsu, Robert D. Lorenz

Research output: Contribution to journalArticlepeer-review

95 Citations (Scopus)


This paper presents a novel variable magnetomotive force flux-intensifying interior permanent-magnet (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 and experimental 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.

Original languageEnglish
Article number6607140
Pages (from-to)1748-1756
Number of pages9
JournalIEEE Transactions on Industry Applications
Issue number3
Publication statusPublished - 2014 Jan 1


  • Flux-intensifying
  • interior permanent magnet (IPM)
  • low coercive force magnet
  • variable magnetomotive force

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering


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