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In this paper, the characteristics of the electromagnetic noise radiated by an external rotor in-wheel motor (IWM) are investigated with the Doppler effect taken into consideration. First, Maxwell stress tensor method is employed to derive electromagnetic forces on the magnet surface. The effect of common current harmonics is also analyzed. Then, a structural model of the rotor is built and modal test is conducted to validate the model. Nodal forces, which are calculated by finite element method, are transferred from the electromagnetic mesh to the structural model for further vibration prediction. Finally, boundary element method is used to calculate the noise radiated by the rotor. In particular, the Doppler effect is considered. The calculated results are validated by the noise test. It is found that the end cap contributes more to the overall noise than the shell, and obvious sound directivity appears in the noise of the IWM. The noise measured perpendicular to the outer end cap is larger than that measured in other directions. In addition, the Doppler effect would induce additional side-frequency components around high-frequency peaks in the external rotor motor. [ABSTRACT FROM PUBLISHER]

A multiphysics model is proposed to predict electromagnetic noise and analyze sound quality of permanent magnet synchronous motor with a variable speed range. First, a two-dimensional electromagnetic finite element model is built and the current during run-up is tested to serve as the input of the model for force calculation. The force is transferred to structural model and the mode superposition method is used to predict vibration. Then, based on the structural mode information and acoustic transfer vector, noise transfer function between electromagnetic force and sound pressure is established. A balanced efficiency and accuracy of noise calculation during run-up is achieved with this function. Finally, psychoacoustical indices are calculated to evaluate the sound quality with the influence of current harmonics into consideration. The calculated vibration and noise are experimentally validated and the errors of noise level in the whole speed range are all below 4 dB. It is also concluded that current harmonics greatly deteriorate the sound quality. [ABSTRACT FROM PUBLISHER]

This paper first derives the characteristics of radial electromagnetic force considering different types of current harmonics. By using two-dimensional fast Fourier transform, the force calculated by the finite element method is decomposed to obtain the frequencies of the force components in specific spatial order. Then, a multiphysics model for electromagnetic vibration and noise calculation is proposed. A modal test is implemented to validate the equivalent stator model and the nonuniform distribution of electromagnetic force acting on the teeth surface is taken into account through the nodal force transfer method. The calculated vibration and noise agree well with those obtained from experimental test. Finally, vibration and noise under different supply currents are investigated, and the variation patterns of the noise and vibration peaks are explained by the amplitude changes of the lowest spatial order force due to current harmonics. It is found that the influence of current harmonics on vibration and noise depends on their effect on the lowest spatial order force, and in order to figure out this effect, the phase angle, phase sequence, and frequency of current harmonics should all be considered. [ABSTRACT FROM AUTHOR]