Torque ripple reduction in brushless DC motor drives

Torque ripple generated in commutation period is the main drawback of Brushless DC (BLDC) motor, and many methods have been studied to solve this problem. In many control method, the torque ripple reduction was considered in the point of current control, which means that if current can be controlled properly, the BLDC motor does not produce any torque ripple. But in this paper, it is proposed that the torque ripple in commutation period of BLDC motor is inevitable, even if the current control is successful. The influence of commutation time to torque ripple and the relationship between commutation time and speed are introduced. This paper deals with torque ripple reduction of BLDC motor from the viewpoint of commutation time and gives a theoretical background to reduce it.