Browse Publications Technical Papers 2019-01-1492

Test and Analysis of Electromagnetic Noise of an Electric Motor in a Pure Electric Car 2019-01-1492

Compared with the low-frequency ignition order of mechanical and combustion noise of the internal combustion engine, the electric drive assembly noise of electric vehicles is mainly the high-frequency whining order noise generated by the electromagnetic force and gear meshing, as well as the high-frequency umbrella noise generated by DC/AC pulse width modulation. Although the radiated sound power is far less than that of an internal combustion engine, the high frequency noise of the motor and the reducer is also annoying. In this paper, the main characteristics of the vibration and noise of an electric motor are obtained by testing it on the vehicle and on the test rig. The main frequency orders are multiplies of motor poles, of which the most significant is the 48th order. The deformation of the motor at the resonance frequency of the 48th order is the breathing mode. Through analysis of electromagnetic force wave, the sources of main orders of motor noise are explained. The most significant order 48th comes from the interaction between rotor magnetic field and stator slots. The amplitude of the electromagnetic force wave of space order 0 is the largest, far higher than that of other space orders. Therefore, the 48th-order noise is revealed to be the most significant, and a strong resonance is generated at the stator's 0-order deformation mode frequency. At last, a scheme for improvement of motor noise is put forward, and the peak value of motor noise is reduced by about 5dB by increasing the air gap between the rotor and stator.


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