Automatic and real time phase advancing in BLDC motor by employing an electronic governor for a desired speed-torque/angle profile

Abstract

When the BLDC motors speed increases, the shape of the current waveform changes in such a way that limits the production of motoring torque and increases torque ripple. At high speeds, the phase current can't reach the desired value due to the self EMF of the motor. Therefore, the torque falls off and the amount of torque ripple increases. To obviate this problem, the phase turn-on angle is advanced in such a way that the phase commutation begins sooner. Since the BLDC drive is a variable speed motor then, the amount of advancing for the turn-on angle should be accomplished automatically according to the speed of the motor. In this respect, this paper introduces an automatic and real-time electronic governor using a microcontroller to achieve this task for a desired speed-torque/advancement angle profile, which is considered to be linear in this study. A linear analysis of the current waveform for the motor under different advancements of the turn-on angle has been performed and the plots are shown. Finally, the experimental results of employing the governor BLDC drive are presented.