Multi-Harmonic Design and Optimization of PMSMs

This paper is about investigating the potential of multi-harmonic design of electric machines. Thereby, multiharmonic refers to the temporal periodic characteristic of linked fluxes and currents of the stator phases in order to ensure highefficient operation with very low torque ripple. The considered PMSM features an interior rotor were magnets are inset to the rotor core. In order to have a fair comparison with conventional PMSMs featuring sinusoidal currents, an optimization scenario is defined where the same outer dimensions as well as magnet and copper volume for both design variants are considered. The use of multiple current harmonics requires a dedicated strategy for evaluating machine designs, as the conventional dqgrid analysis cannot be applied. The adopted approach is depicted and results of the optimization are illustrated. Moreover, a comparison of measurements for prototypes is presented. Results reveal that adding more degrees of freedom in terms of multiple harmonics can give significant improvements for performance measures efficiency and torque ripple. This particularly holds if the harmonics are already considered throughout the machine design process, rather than only at post-processing stage.