Analysis of commutation torque ripple of BLDC motors and a simple method for its reduction

This paper presents methods for analyzing and reducing commutation torque ripple of brushless DC (BLDC) motors in 120° elec. conduction mode. Due to voltage vector changes in every 60° elec. in BLDC drives, the current is commutated from one phase to another which results in electromagnetic torque fluctuations called commutation torque ripple. In this paper, commutation torque ripple in BLDC drives is analyzed and precise equations for calculating torque ripple are presented. Then, a simple method for reducing commutation torque ripple by modifying the voltage of decaying phase in commutation interval is presented. The advantages of proposed method are its simplicity and independency to commutation period recognition. The presented torque ripple analysis and the proposed method for torque ripple reduction are validated by dynamic simulation of a 600W BLDC motor.