Analytical method for magnetic field calculation in a low-speed permanent-magnet harmonic machine

Linni Jian, Guoqing Xu, Chunting Chris Mi, K. T. Chau, C. C. Chan

Research output: Journal article publicationJournal articleAcademic researchpeer-review

84 Citations (Scopus)


Magnetic-gearing effect has become increasingly attractive when designing direct-drive low-speed permanent-magnet machines. The machines derived from the magnetic-gearing effect can be termed as harmonic machines. Unlike the conventional types, harmonic machines rely on the field harmonics to achieve energy conversion and transmission. The detailed knowledge of the field distributions in the air gap is vitally important for predicting and optimizing its performance. In this paper, we present an analytical approach to calculate the magnetic field distribution in a low-speed permanent-magnet harmonic machine. A series-slot model which is composed of a group of partial differential equations concerning the scalar magnetic potential is built up. Then, the field solutions are obtained by using the method of separating variables and analyzing the field boundary conditions. Finally, the flux densities are derived from the scalar magnetic potentials. All the results agree well with those obtained from the finite element method.

Original languageEnglish
Article number5764827
Pages (from-to)862-870
Number of pages9
JournalIEEE Transactions on Energy Conversion
Issue number3
Publication statusPublished - Sept 2011


  • Analytical calculation
  • direct drive
  • harmonic machine
  • low speed
  • magnetic gearing
  • permanent magnet

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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