Low Vibration Design and Investigation of an Interior Permanent Magnet Motor in the Perspective of the Saliency Ratio

To address the issue of increased electromagnetic vibration in permanent magnet (PM) motors for electric vehicles under flux-weakening speed extension operation, this paper proposes a low-vibration design method for PM motors from the perspective of saliency ratio. First, by establishing a theoretical model for vibration analysis under flux-weakening operation, it reveals the vibration mechanism whereby high-order armature magnetomotive force (ARM-MMF) harmonics under flux-weakening operation leads to enhanced radial electromagnetic force (REF). Second, an in-depth investigation into the intrinsic relationship between saliency ratio and ARM-MMF is conducted. This study proposes a novel methodology to design key ARM-MMF harmonics that induce significant electromagnetic vibration from the perspective of the saliency ratio. An innovative rotor topology featuring elliptical-arc composite flux barriers is developed to implement this approach. Furthermore, and synergistic optimization is performed with the saliency ratio and torque as optimization objectives to balance vibration suppression and torque output performance. Finally, a prototype is manufactured and tested. Both theoretical and experimental analyses validated the effectiveness of the motor and the proposed design method.