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This study analysed the characteristics of electromagnetic force and noise of claw pole alternators with different pole and slot combinations and different phase number. The magnetic flux density in the airgap was first derived based on the magnetomotive force and permeance. Then the electromagnetic force was obtained using Maxwell stress tensor method. According to the analytical model, the spatial order and frequency of electromagnetic force can be expressed as the function of pole‐pairs number p, slot number s and phase number m. Afterwards, the electromagnetic noise of three different alternators was tested in a semi‐anechoic chamber. Combined with the 2D fast Fourier transform of electromagnetic force, the main force harmonics that caused the electromagnetic noise were distinguished. Finally, the relationship between the frequencies of electromagnetic force and noise and the number of pole‐pairs and phase were established. Analysis result shows that for m‐phase 2p‐pole/s‐slot integer slot claw pole alternators, the spatial order of electromagnetic force is kp (k = 0, 1, 2, 3,...) and the corresponding frequency of these force harmonic is [±2mpk′ + (±kp)]fr (k′ = 0, 1, 2, 3 ...). The main order (frequency domain) of electromagnetic noise is 2mp which is independent of the slot number. [ABSTRACT FROM AUTHOR]

This study provides a detailed finding of the influence of pole and slot combinations on vibration and noise in external rotor axial flux in‐wheel motors (AFWMs). Firstly, electromagnetic force exerted on the surface of permanent magnet is discussed and a two‐dimensional fast Fourier transformation is implemented to analyse its spatial distribution and frequency characteristics. Then, a multiphysics model is developed to predict the vibration and noise and figure out the main origin from the perspective of electromagnetism. The influence of pole and slot combinations on vibration and noise is also analysed via the proposed model. Finally, the effect of load on vibration and noise in AFWMs is further investigated. It turns out that zeroth spatial order of axial electromagnetic force is the main origin of vibration and noise in axial flux motors, which is quite different from radial flux motors. Moreover, AFWMs with larger lowest common multiple (LCM) of pole number (2p) and slot number (Qs) show lower noise level and for the motors that satisfy LCM(2p,Qs) ≠ 6p, vibration and noise are greatly influenced by load. This study provides guidance for the design of low noise AFWMs. [ABSTRACT FROM AUTHOR]