A Numerical Prediction Model for Vibration and Noise of Axial Flux Motors

A numerical procedure to predict vibration and acoustic noise due to electromagnetic excitation forces in an axial flux motor (AFM) is presented and applied to a motor with ferrite magnets for electric vehicles. The methodology includes the calculation of radial magnetic forces exerted on stator inner surfaces using electromagnetic solver to account for vibration and noise of the motor. Fundamental and high-order harmonics of the magnetic forces are then obtained via fast Fourier transform process. Structural analyses such as modal and harmonic analysis are conducted to investigate natural resonant frequencies of the motor system and modal shapes highly responsible for vibration of the frame and acoustic noise. Magnitudes of vibration displacement on the motor housing surface and sound pressure level at a given point in the space are predicted using harmonic and acoustic analyses, respectively. Motor performance tests were conducted to validate the model, and the results showed that the model predictions agree well with the observations from the experiments.