Pulse Width Modulation Methods for Minimizing Commutation Torque Ripples in Low Inductance Brushless DC Motor Drives

Abstract

This article proposes pulse width modulation (PWM) methods for low inductance brushless dc (BLDC) motor drives that minimize the commutation torque ripples. An uneven current of noncommutation phase generates the commutation torque ripples. In the low inductance BLDC motor drives, two types of time delays in PWM also induce critical torque ripples. In this article, the analyses of the time delays in PWM and their effects are introduced. Then, two PWM methods are proposed to eliminate the time delays in the commutation region and the conduction region, respectively. The commutation period is controlled to be synchronized to the switching period. In addition, the proposed methods synchronize the switching period to the commutation interrupt. As a result, the proposed methods effectively maintain the minimum commutation period as well as minimize the commutation torque ripples in the low inductance BLDC motor drives. The validity of the proposed methods is demonstrated by the simulation and experimental results in various driving conditions. The results show that the commutation period is remarkably shortened and the commutation torque ripples are reduced by 27.6% in comparison to the conventional method.