Improving the Crest of Radial Force for Pole-Frequency Vibration Suppression in PM Machines

The pole-frequency electromagnetic (EM) vibration of surface-mounted permanent magnet (PM) synchronous motor is primarily affected by the fundamental component of air gap flux density, which is challenging to mitigate. This article proposes a novel type of PM rotor for suppressing pole-frequency EM vibration. First, the generation principle of pole-frequency radial air gap force density (AGFD) is derived. Subsequently, a novel magnet structure with a low center and high side shape is proposed to reduce the pole-frequency harmonic by improving the crest of radial AGFD. Then, the tooth modulation effect is considered, compared with the bread-loaf PM rotor, and the pole-frequency harmonics of the tooth forces and moment of the proposed rotor are further analyzed. Finally, the 24-slot/ 28-pole prototypes with different PM rotors are manufactured, and several simulations and vibration test results are conducted to validate the proposed PM in suppressing pole-frequency EM vibration.