Torque ripple reduction in BLDC motor based on a PWM technique for open-end winding

The article presents a modulation method for BLDC motors with unconnected windings. This method uses two full bridges (or three 12-switch H-bridges). The use of the described modulation enables reducing the motor current variable and increasing (fourfold in relation to the switching frequency) the motor current ripple frequency. The most important benefit of using a 12-switch inverter is the twofold reduction of the dc-link voltagewhilemaintaining the rated rpm (voltage reduction in comparison to a typical supply method). A voltage reduction causes a reduction in losses on semi-conductor elements. The article also demonstrates that the proposed modulation technique significantly shortens the time of current commutation between windings.