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In this paper, to optimize vibration of the fractional slot concentrated winding interior permanent magnet (FSCW-IPM) motor for electric vehicles (EVs) without sacrificing any torque performance, modifications of iron-core structures are proposed. First, the effects of basic stator/rotor auxiliary slots on torque, cogging torque, torque ripple, and 2 nd order spatial harmonic of radial force are investigated by finite element analysis (FEA). The combinations of stator/rotor auxiliary slots, which can optimize vibration with maintained torque, are analyzed. To improve torque and optimize vibration, uneven airgap rotor is proposed. With variation of the uneven air-gap rotor, torque improvement and vibration reduction do not contradict each other. The vibration levels of FSCW-IPM motors are calculated by magnetic-mechanical coupling models, while the peak vibrations are optimized with the proposed methods. Inductance, torque, and vibration experiments of the FSCW-IPM motor with the uneven airgap rotor are performed. The theoretical and experimental results both validate effectiveness of the proposed methods for torque improvement and vibration optimization.
Wu et al. (Mon,) studied this question.