Design and analysis of a SPM in-wheel motor for the propulsion of electric buses

The paper deals with the electromagnetic analysis of in-wheel motors with surface permanent magnets and outer rotor. First the torque performances of two motors with 24 and 36 poles are evaluated by 2D FEM parametric solutions, in order to identify the configuration with the best compromise between torque ripple and torque/weight ratio. Then a non-linear mathematical model is defined to simulate the motor performance in dynamic conditions. The model is based on the reproduction of the instantaneous torque and flux linkages by elaborating the data of 2D FEM magnetostatic analyses. In particular, a simplified procedure is developed to evaluate the end-winding fluxes. The comparison with the results of the 3D FEM solutions evidences the accuracy of the proposed procedure in the estimation of the model parameters, with considerable time savings with respect to 3D FEM analyses.