Analysis of torque ripple in BLDC motor with commutation time

Torque ripple generated in commutation period is the main drawback of BLDC Motor, however, which deteriorates the precision of BLDC Motor. And many methods to solve this problem have been studied. 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. Torque model considered with decaying phase back EMF is introduced and the causes of commutation torque are analyzed. 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.