Comparing Force Density per Unit Area Among IPM/SPM SM and Vernier SM

In this paper, tangential force density at the same air-gap, diameter, stacking length, and input current is shown to have a fair comparison in IPM motor, SPM motor, synchronous motor with winding, synchronous reluctance motor, induction motor, flux switching motor, flux reversal motor, SRM, 2 air gaps/1 coil vernier motor and 2 air gaps/2 coils (inner and outer coils) vernier motor. The tangential force density $\mathrm{F}_{\mathrm{td}}$ can be derived in order to obtain some feeling for the magnitude of the tangential force. Under the same conditions, with aid of the 2D finite element analysis, tangential force density for rotating electrical motors is calculated. To verify the validity of the analyses, a prototype of vernier motor with 2 air-gaps and 2 coils (inner and outer coils) is fabricated and tested. Experimental shows that the tangential force density of vernier motor with 2 air-gaps and 2 coils is significantly higher than the conventional SPM motor. In the future, the overall comparison in terms of losses, power factor and thermal analysis using both 2D and 3D analyses will be taken into account.