Vibration characteristics due to electromagnetic excitation force accompanied by modulation

Abstract

Fan motors are used for cooling various devices such as PCs and data servers. Fan motors generally use inverters to control rotation speed for the purpose of energy saving and variable speed. However, the pulse width modulation control of the inverter is a source of excitation, and the radiation noise of the fan motor, whose fundamental frequency is the carrier frequency, becomes a problem. To solve this problem, modulation of the electromagnetic excitation force is used, but the actual change in noise is often not sufficient to improve the sound quality. Therefore, this study confirms the characteristics of resonance phenomena caused by CF in PWM control using noise tracking analysis and ODS analysis using a laser Doppler vibrometer.