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Noise reduction of axial‐flux motors by combining various pole‐arc coefficients and circumferential shifting of permanent magnets: analytical approach

The electromagnetic noise of an axial-flux in-wheel motor (AFWM) is reduced by combining various pole-arc coefficients and circumferential shifting of permanent magnets (PMs) here. First, the analytical model of the air-gap magnetic field for the AFWM with various pole-arc coefficients and circumferential shifting of PMs is established. The influence of edging effect and stator slotting is taken into account through the radial correction function and complex relative permeance function, respectively. Subsequently, the torque and electromagnetic noise of the AFWM are derived analytically. A multi-objective optimisation of the AFWM is then implemented by the NSGA-II (non-dominated sorting genetic algorithm) based on the proposed analytical approach. Finally, the electromagnetic performance and vibroacoustic characteristics of the initial and optimised motors are compared and analysed. The results show that the proposed method by combining various pole-arc coefficients and circumferential shifting of PMs can reduce the noise of axial-flux motors effectively, without sacrificing the output torque. This study is of great significance for the vibration and noise reduction of axial-flux motors.