Unsymmetrical Pole Design vs Skewing for improving NVH Characteristics and Performance of High Speed PMSM Electric Machines

Electric machines with increased efficiency and power density requirements are the norm for the automotive industry. This has lead to an increased demand on PM-SyR machine topology even though they exhibit high torque ripple NVH issues. In this paper, a comparison between conventional skewing technique and asymmetrical pole design is carried out with an aim to reduce the torque harmonics. In particular, flux barrier shift method is considered which consists of moving the individual poles of a multi-polar machine in an asymmetric manner to reduce torque harmonics. The following technique is implemented in a PM-SyR machine with V-shaped flux barriers with the help of multi-objective genetic algorithm based optimization process. At the end, torque ripple and radial forces for the critical space-time orders are compared along with performance and loss figures.