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

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 degrees phase-belt toroidal winding (60 degrees 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 degrees phase-belt toroidal winding (30 degrees TW) and 60 degrees 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 degrees phase-belt toroidal winding. The experimental results indirectly verify the feasibility of 60 degrees 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 degrees TW is improved in comparison to the six-phase PMSM with 30 degrees TW. Index Terms-60 degrees phase-belt toroidal winding, axial flux, six-phase permanent magnet synchronous motor, torque density