This paper has analyzed the vibration and acoustic noise caused by electro-magnetic torque fluctuation of brushless DC motor (BLDC motor). Through the analysis of electromagnetic torque, its components were determined: this paper proposed that electro-magnetic torque consists of a cyclical fluctuation whose harmonic frequencies are 6n (n=1, 2, 3……) times of phase current frequency. By measuring and analyzing the frequency of the noise signal, the actions of the electro-magnetic torque fluctuations on the vibration and acoustic noise are determined. Driving the BLDC motor with sinusoidal wave current to eliminate the electro-magnetic torque fluctuation, the vibration and acoustic noise of brushless DC motor are minimized effectively.
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