Numerical simulation and optimization for electromagnetic noises of permanent magnet synchronous motors in vehicles

In the paper, the numerical simulation is conducted on the motor electromagnetic force firstly. Radial force waves of the motor are the main reason for causing electromagnetic vibration and noise. Then, electromagnetic forces are mapped into a structural model for computing electromagnetic vibration. Computational results are compared with experimental results, so the correctness of the computational model is verified. Then, electromagnetic noises are computed according to the vibration data of the motor. Electromagnetic noises of the motor are axis-symmetric in plane X and plane Z. In plane Y, the electromagnetic noise of the motor is skew-symmetric relative to a 45 degrees angle. In plane X and plane Z, the noise is caused by the vibration of the end cap, while noise in plane Y is caused by electromagnetic radial forces. In addition, the motor electromagnetic noise has an obvious directivity. The motor also has obvious peak noises at 300 Hz, 400 Hz, 500 Hz, 600 Hz, 900 Hz, 1200 Hz, 1500 Hz and 1800 Hz. Peak noises are corresponding to 6th, 8th, 10th, 12th, 18th, 24, 30th and 36th orders of the motor. Finally, modal participation factors of the motor within the analyzed frequency are computed. Results showed that modals at the 3rd, 5th, 12th and 15th orders of the motor have most obvious impacts on electromagnetic noises. In particular, the 3rd order modal shape obviously affects electromagnetic noises. The electromagnetic noise is reduced by applying reinforced bars and damping layer to these key modal shapes, especially the peak noise. The total noise of the original structure is 58 dB, while the total noise of the improved structure is 52.3 dB. Obviously, the total noise is reduced by 9.8 %.