Torque Ripple Reduction in Specific Directions for Concentrated Winding IPM Motors Using Cogging Torque Phase Shift by Asymmetric Flux Barriers

This paper proposes a novel finding for asymmetric flux barriers and their use in torque ripple reduction. Although previous studies have reported torque enhancement by applying asymmetric flux barriers, the mechanism remains unclear with respect to torque ripple. In this study, the torque ripple component is separated into the cogging and load torques, and the phase of the cogging torque is shifted by an asymmetric flux barrier. For example, in concentrated winding motors with pole-to-slot ratio of 2:3, torque ripple reduction under low- and high-load conditions is not compatible because the harmonic orders of the two torques overlap. It can be expected that the proposed phase shifting effect of the cogging torque allows for both conditions of torque ripple reduction. To demonstrate the validity of the proposed mechanism, a numerical validation is performed using topology optimization and frozen permeability method. In addition, the experimental verification using prototype motors is conducted to demonstrate the validity of the numerical verification.