Parametric optimization of rotor outer-contour shaping for a hairpin-winding V-shaped interior permanent magnet synchronous motor with a non-uniform air gap

To improve the sinusoidal characteristics of the air gap flux density and reduce torque ripple and losses, this paper proposes a rotor outer-contour parametric optimization method for a V-shaped interior permanent magnet synchronous motor with hairpin windings and a non-uniform air gap structure. Based on a sinusoidal reference waveform, a non-uniform air gap rotor outer-contour model is established, with the shaping angle and shaping depth selected as design variables. The optimal parameter combination is determined through parameter scanning, and the electromagnetic performance of different models is evaluated under both no-load and loaded conditions. According to the findings of this study, under no-load conditions, the air gap magnetic flux distortion rates for the original model (uniform air gap), Model A (initial model obtained via parameterized scanning), and Model B (optimal model obtained via parameterized scanning) are 28.93%, 24.52%, and 21.86%, respectively. These results show that Model B exhibits the most effective harmonic suppression. Under a load ( I = 20 A, β = 20°), Model B achieves an average torque of 16.93 N·m, reducing torque ripple from 11% in the original model to 7.9% (approximately 28% reduction). When the motor operates at 6000 r/min under the same load conditions, the stator core loss of Model B decreases from 516.64 to 444.09 W, and the eddy current loss decreases from 386.88 to 301.57 W, compared with the original model. These results demonstrate that the proposed method effectively suppresses torque ripple and losses caused by low-order harmonics while essentially maintaining output capability. Furthermore, by introducing only a limited number of geometric design variables, the method exhibits good engineering feasibility and holds significant application potential.