Abstract
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° 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 %.
Highlights
Regarding many advantages in wide high-efficiency regions, high torque density and compact structures, permanent magnet synchronous motors have become one of main driven motors in vehicles
(1) Electromagnetic noises: Air gap magnetic force waves act between a stator and a rotor, which will cause unbalanced electromagnetic force waves with time and space
Electromagnetic forces are mapped into a structural model for computing electromagnetic vibration
Summary
Regarding many advantages in wide high-efficiency regions, high torque density and compact structures, permanent magnet synchronous motors have become one of main driven motors in vehicles. Based on multi-physics field platform in ANSYS, Zheng [13] studied electromagnetic vibration and noise characteristics of a permanent magnet synchronous motor and analyzed main sources which might cause serious electromagnetic noises from two aspects including electromagnetic force and motor structures. Based on electromagnetic field analysis theories, Luo [15] conducted finite element simulation of radial force waves of a permanent magnet brush-less motor, in order to conduct dynamic modeling and simulation research on the motor stator. Based on the numerical simulation, with low noise and high flow rate as the optimization goals, aerodynamic noise optimization and noise reduction researches were conducted on radial grating distribution angles of the front end cap of the AC generator They did not obtain obvious noise reduction effects in the full frequency band through the optimization measures. Some measures are adopted to reduce electromagnetic noises of the motor, where noise reduction effects are very obvious
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