Low-torque ripple design of a ferrite-assisted synchronous reluctance motor

This study illustrates the design of a low-torque ripple ferrite-assisted synchronous reluctance machine. The design strategy initially adopts a simplified analytical model in order to select the optimal values for the flux barrier angles that mainly affects the torque ripple. Then, synchronous reluctance rotor geometries selected on the basis of analytical results are analysed by finite elements (FEs) simulations. The simulated geometries are provided by ferrite permanent magnets (PMs) to enhance machine performance. The optimisation steps are properly coordinated in order to realise the maximum reduction of the torque ripple, taking into account the PM quantity and the flux barrier shape as well as the demagnetisation risk. Two optimal rotor geometries are presented and compared in terms of torque ripple by FEs simulations. Then, the comparison have been extended to other machine characteristics (as high-frequency saliency and demagnetisation tolerance) to the aim of selecting the more promising one. Available measurements on prototypes are reported to confirm the simulation results and the design approach.