Radiated noise analysis in high-speed permanent magnet synchronous motors with rotor eccentricities

At present, the noise problem of new energy vehicle motors has become more and more prominent. Electromagnetic vibrations and noise generated by permanent magnet synchronous motors (PMSMs) are a hot issue studied by designers, and electromagnetic force waves, the excitation source of vibration and noise, are very important. This paper focuses on the noise, vibration, and harshness (NVH) generated by the electromagnetic forces in PMSMs with static and dynamic rotor eccentricities. When the rotor is eccentric, the electromagnetic forces have the spatial distribution of the harmonic components, and previous research has indicated that the amplitudes of the upper and lower sidebands are distinct. The eccentricity of the rotor influences the gap permeance, the operating point of the rotor magnets, the gap magnetic flux density distribution, and therefore the electromagnetic force and its spectral distribution. In this paper, the NVH response for dynamic and static eccentricities based on the radial magnetic force harmonics is estimated. The harmonic properties of force are examined with the use of the fast Fourier transform (FFT). The acoustic noise under several degrees of eccentricity is then predicted using a multi-physics model. Induced force harmonics of lower space orders are found to be significantly amplified by dynamic rotor eccentricity, with dominating noise peaks shifting to the frequency band around the lower natural frequencies.