Reduction of commutation torque ripple in a brushless DC motor drive

This paper describes the reduction in torque ripple due to phase commutation of brushless dc motors. With two-phase 120deg electrical conduction for the inverter connected to the conventional three-phase BLDC machine, the commutation torque ripple occurs at every 60 electrical degrees when a change over from one phase to another occurs. This effect increases the commutation time at higher speeds which increases the torque ripple. The torque ripple is reduced by changing the switching mode from 120deg to a dual switching mode with 120deg switching at lower speeds and 1800 electrical for the inverter at higher speeds.