Unbalanced magnetic pull due to asymmetry and low-level static rotor eccentricity in fractional-slot brushless permanent-magnet motors with surface-magnet and consequent-pole rotors

David G. Dorrell, Mircea Popescu, Dan M. Ionel

Research output: Contribution to journalArticlepeer-review

133 Scopus citations

Abstract

We report on an investigation into the unbalanced magnetic pull (UMP) in ferrite-magnet fractional-slot brushless permanent-magnet motors due to either magnetic asymmetry or static rotor eccentricity. We justify the work in terms of the establishment of total indicated runout (TIR) tolerance and use 10% eccentricity as the nominal tolerance. The UMP will generate force and vibration, which causes wear. We investigated several machines with different pole numbers, slot numbers, and winding arrangements. Some of the windings contain sub-harmonics, and we found these to be more susceptible to UMP when there is rotor eccentricity and also to produce vibrating UMP. We found that consequent rotor poles produce high UMP under centered and rotor eccentricity conditions. We conducted detailed finite-element studies to calculate the UMP.

Original languageEnglish
Article number5427139
Pages (from-to)2675-2685
Number of pages11
JournalIEEE Transactions on Magnetics
Volume46
Issue number7
DOIs
StatePublished - Jul 2010

Keywords

  • Brushless permanent-magnet motors
  • Fractional slot
  • Unbalanced magnetic pull

ASJC Scopus subject areas

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

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