Rotor Eddy-Current Losses Reduction in an Axial Flux Permanent-Magnet Machine

Werner Jara, Pia Lindh, Juan Antonio Tapia, Ilya Petrov, Anna Kaisa Repo, Juha Pyrhonen

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


A novel rotor structure for a tooth-coil-winding (concentrated winding) open-slot axial-flux permanent-magnet (PM) machine that reduces the eddy currents and increases the main flux linkage is proposed in this paper. A composite-body-based rotor assembly and a steel-laminated layer inserted on top of the magnets are used to reduce eddy-current losses in the PMs. A prototype of an axial flux generator for a heavy-duty vehicle following this structure is optimized, analyzed and measured. The tooth coil windings produce high-amplitude harmonics in the air gap and the large slot openings reduce the rotor flux. Consequently, a rotor structure that decreases the amount of harmonics travelling through the magnets is required. Steel laminations covering the magnets have positive effects on both phenomena. Two-dimensional and three-dimensional finite-element analysis is used to verify and optimize the geometry of the laminations. Computations are verified by experimental measurements of a 100 kW test machine prototype.

Original languageEnglish
Article number7442573
Pages (from-to)4729-4737
Number of pages9
JournalIEEE Transactions on Industrial Electronics
Issue number8
StatePublished - Aug 2016
Externally publishedYes


  • Axial flux (AF) machines
  • Tooth coil windings (TCWs)
  • eddy currents
  • finite-element analysis (FEA)
  • magnetic losses
  • permanent-magnet machines
  • rotor losses
  • synchronous machines


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