Analytic Analysis on Commutation Angle of Brushless DC Motors with 120° Voltage Source Inverter

摘要

For 120° voltage source inverter (VSI), commutation angle is the conduction angle of free-wheel diode. When brushless DC motor (BLDCM) operates sensorlessly based on detecting the zero-crossing of back-EMF waveform, commutation angle of VSI must be significantly less than 30°. However commutation angle is always larger than 30° in high-speed BLDCM and deep-see BLDCM, which makes scnsorless operation unreliable. Therefore, analysis on commutation angle is indispensable for system design. This paper analytically analyses the influence factors of commutation angle. Conclusions independent of special cases are presented. A convenient approach for estimating commutation angle is proposed and the accuracy is verified by experimental result.