Vibration Optimization of FSCW-IPM Motor Based on Iron-Core Modification for Electric Vehicles

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.