Commutation Torque Ripple Analysis and Reduction Through Hybrid Switching for BLDC Motor Drives

Permanent magnet brushless dc (BLDC) motor drives are widely used in high performance applications where torque smoothness is essential. In this paper, the reduction in commutation torque ripple due to phase commutation of brushless dc motor is described. In a conventional three-phase BLDC machine with two-phase 120deg electrical conduction, commutation torque ripple, which occurs at every 60deg electrical degrees changing over of load current from one phase to another. The torque ripple increases at higher speeds due to increase in commutation time. On the other hand for 180deg switching mode of phase currents, the torque ripple reduces at higher speeds but shows substantial increase at lower speeds. In this paper a hybrid switching characteristics is proposed at lower and higher speeds for satisfactory operation. Computer simulation and suitable experiments has been shown to validate the concept.