A Commutation Time Optimized Method to Reduce Torque Ripple of BLDCM in Generator Mode for Hoist Application

Because of their high efficiency, high power density, and other advantages, brushless direct current motors (BLDCMs) are employed in a wide range of industries. This makes BLDCMs an excellent choice for use in aviation hoists. However, the torque ripple is a noticeable drawback of BLDCM. Although there are several potential reasons to cause torque ripple, the commutation among them plays a significant role. There have been many studies done on lowering commutation ripple, nevertheless majority of them only pay attention to the commutation ripple that occurred in the first or third quadrants. The other two quadrants, where the BLDCM in the hoist application runs as a generator to descend cargos, do not get enough attention. In these two quadrants, although the current ripple of noncommutation phase is an important reason for causing torque ripple, the other two reasons related to commutation time should have also been noticed. Existing papers could only reduce the current ripple of noncommutation phase, but the other two causes of torque ripple could not be taken into account at the same time. The torque ripple related to commutation time is analyzed in detail, and a commutation time optimized method based on the improved PWM scheme is proposed to simultaneously reduce the torque ripple caused by all three reasons.