Analytical-Based Design Framework for Outer Rotor Consequent-Pole Permanent Magnet Machine

This paper presents an analytical-based design framework for an outer rotor in-wheel consequent pole surface mounted permanent magnet (CP-SPM) motor for small size (maximum 800 kg) electric vehicles (EVs). To avoid computational burden associated with Finite Element (FE)-based design and optimization process, a two-dimensional (2-D) analytical model is proposed and paired up with a multi-objective optimization algorithm. In the presented analytical model, the effects of stator slots/teeth and rotor saliency are modeled by equivalent magnetizing currents, and the governing Maxwell's equations are solved in a slotless and non-salient structure (i.e., slotless stator and cylindrical rotor). Next, the presented analytical model is linked with a multi-objective optimization algorithm to bring (i) material costs, (ii) efficiency, and (iii) the ratio of the average torque to the torque ripple to desired levels. To assess the suitability of the presented design for in-wheel EV applications, the performance characteristic of the presented outer rotor CP-SPM machine is compared against the SPM machine counterpart. For validation purposes, the prototype of the optimized CP-SPM in-wheel motor is made and tested in the laboratory.