A novel high torque density six-phase axial-flux permanent magnet synchronous motor with 60° phase-belt toroidal winding configuration

Jikai Si, Can Feng, Rui Nie*, Yihua Hu, Yingsheng Li

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The three-phase permanent magnet synchronous motor (three-phase PMSM) has gained much popularity in many applications due to its various advantages. In addition, due to the good fault tolerance, simple inverter circuit structure and high torque density, the six-phase PMSM has better prospects than three-phase PMSM in biomedical devices, electric vehicles and other fields with high reliability requirements. In this study, a six-phase axial-flux PMSM inherently without cogging torque is proposed to improve torque density, which equips the 60° phase-belt toroidal winding (60°TW) and slotless stator core. Based on the same effective volume, permanent magnet material, power grade and the other major motor parameters, two six-phase PMSMs with 30° phase-belt toroidal winding (30°TW) and 60°TW are designed, respectively. The armature reaction field, air gap magnetic density, back-electromotive force, output torque, loss characteristic and torque-speed characteristic are compared by using three-dimensional (3D) finite-element models in detail. Finally, the experimental test is carried out using the prototype of three-phase PMSM with 120° phase-belt toroidal winding. The experimental results indirectly verify the feasibility of 60° phase-belt toroidal winding and correctness of 3D FEM. The 3D FEM analysis results are presented to show that torque density of the proposed six-phase PMSM with 60°TW is improved in comparison to the six-phase PMSM with 30°TW. Index Terms—60° phase-belt toroidal winding, axial flux, six-phase permanent magnet synchronous motor, torque density.

Original languageEnglish
Pages (from-to)41-54
Number of pages14
JournalIET Electric Power Applications
Issue number1
Early online date16 Sept 2021
Publication statusPublished - 17 Dec 2021

Bibliographical note

© 2021 The Authors. IET Electric Power Applications published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.


  • air gaps
  • density
  • electric potential
  • electrochemical analysis
  • fault tolerance
  • finite element analysis
  • invertors
  • losses
  • machine windings
  • permanent magnet motors
  • permanent magnets
  • stators
  • synchronous motors
  • torque

Cite this