Research of stator displacement technique in multistage axial-flux permanent magnet machines

Axial flux permanent-magnet machines have gained popularity in the last few decades because of their higher torque at low speed and better power density compared with radial flux machine, moreover, due to its inherently short axial length, they find applications where the used conventional PM machines are not appropriate, such as hybrid traction motors. However, the major undesired effects are the cogging torque due to high frequency flux pulsation caused by air gap reluctance variation and the lack of field weakening capability due to a fixed magnetic excitation which limits the drive's maximum speed and becomes a significant limitation for both radial and axial flux PM machines. In this paper, a new multistage axial flux permanent magnet will be proposed, and based on the multistage axial flux permanent magnet synchronous machine (M-AFPM), the stator displacement technique will result in a multi-phase machine with little mutual inductance between two stators and improve the torque density and quality, moreover, it can reduce the cogging torque by half at best, and a new switch-phase connection technique combine the stator displacement is proposed for extending the flux-weakening capability. The performance of the multi-phase M-AF-PM will be studied in this paper by the 3D-FEA. Based on a 2kW-1000rpm 10-pole 12-open-slot prototype with stator displacement, the experimental study will is developed. And the comparison between the experiments and 3D-FEA results will be proposed in this paper.