Controllability analysis of torque ripple due to phase commutation in brushless DC motors

In a brushless DC motor (BLDCM) drive system, it has been well noted that phase-current commutations and the imperfection of back electromotive force (EMF) are usually the major causes of electromagnetic torque pulsation. With the extension of BLDCM applications, many methods have been presented to attenuate the pulsation and, the most popular ones are optimizing phase-current waveforms by implementing different strategies in an inner closed-loop of current control. However, few studies are found on the controllability of phase-currents in a BLDCM system. In this paper, the elements that have effect on the control of phase-currents will be evaluated by considering the machine and its inverter supply. The operation zone that the torque pulsation can be attenuated are described analytically.