Field weakening for radial force reduction in brushless permanent-magnet DC motors

Guandong Jiao, Christopher D. Rahn

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


In brushless permanent-magnet de (BLDC) machines, the attraction between the rotor permanent magnets and the stator iron causes radial stator forces that excite the stator structural response and radiate unwanted acoustic noise. In this paper, we develop an analytical model that predicts rotor torque and radial force ripple as functions of the stator currents. The model shows that field weakening of sinusoidally commutated BLDC machines can reduce radial forces but requires higher currents to maintain the desired torque. We confirmed the analytical results numerically on a BLDC motor using ANSYS finite-element analysis and found a 30% reduction in force ripple at no load.

Original languageEnglish (US)
Pages (from-to)3286-3292
Number of pages7
JournalIEEE Transactions on Magnetics
Issue number5
StatePublished - Sep 2004

All Science Journal Classification (ASJC) codes

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


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