Dual-mode switching technique for reduction of commutation torque ripple of brushless dc motor

In this study, the reduction of commutation torque ripple because of phase commutation of brushless dc (BLDC) motor is described. In a conventional three-phase BLDC machine with 120° electrical conduction, commutation torque ripple occurs because of changeover of load current from one phase to another at every 60 electrical degrees. Similar is the case for 180° conduction mode because of change of phase currents at 60° intervals. A detailed analysis shown in this study reveals that the torque ripple reduces for 180° switching mode at higher speeds because of reduction of both torque ripple magnitude and commutation time, compared to the 120° conduction mode of the inverter. In this study, a dual-mode switching technique is proposed to optimise the commutation torque ripple of the machine. Suitable computer simulations and experiments are performed to validate the proposed concept.