Unbalanced magnet pull in large brushless rare-earth permanent magnet motors with rotor eccentricity

David G. Dorrell, Min Fu Hsieh, Youguang Guo

Research output: Contribution to journalArticle

78 Citations (Scopus)


Permanent magnet motors are now the focus of application in larger drive and generator systems. They often utilize rare-earth magnets where attractive forces are large and unbalanced magnetic pull (UMP) will be generated even when unexcited. In this paper, a 4-pole machine design is utilized which has either surface magnets or consequent poles. Dynamic eccentricity up to 80% is put into the machine model and a variety of simulations carried out to investigate the UMP. It is found that with strong and thick magnets the machine is robust and the UMP is almost load independent. The consequent pole rotor arrangement produces much higher UMP when the dynamic eccentricity aligns with the steel poles. In the simulations, the different stress components are investigated to assess the validity of a commonly held approximation where the radial force is taken to be a function of the square of the radial air-gap flux.

Original languageEnglish
Article number5257290
Pages (from-to)4586-4589
Number of pages4
JournalIEEE Transactions on Magnetics
Issue number10
Publication statusPublished - 2009 Jan 1


All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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