Analytical prediction of cogging torque in surface-mounted permanent-magnet motors

D. Lin, Siu Lau Ho, Weinong Fu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

33 Citations (Scopus)


We present a new approach to computing cogging torque based on only one analytical field solution in surface-mounted permanent-magnet (PM) motors. We use conformal transformation to compute the magnetic field created by the permanent magnets in the air gap with a single slot. Then, we derive the cogging torque due to the single-slot effect at different rotor positions directly from the 2-D analytical field solution. The total cogging torque is synthesized from the contribution of each slot. We have applied our approach to predicting the cogging torque of two surface-mounted PM motors, one with 4 poles, 24 slots and the other with 42 poles, 36 slots. The predicted cogging torques for both applications agree well with those obtained from 2-D finite-element analysis.
Original languageEnglish
Article number5208505
Pages (from-to)3296-3302
Number of pages7
JournalIEEE Transactions on Magnetics
Issue number9
Publication statusPublished - 1 Sept 2009


  • Analytical field solution
  • Cogging torque
  • Conformal transformation
  • Permanent-magnet machine

ASJC Scopus subject areas

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


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