Improved Switching Strategy for a Single-Phase Brushless Direct Current Motor and its Impact on Motor Efficiency

Advancing the turn-off angle of the phase current of brushless direct current (BLDC) motors is a common control practice to improve their behavior and efficiency (reduction of current peaks, copper losses, and breaking torques). This paper investigates a refined switching strategy for a single-phase BLDC motor with bifilar winding to increase the energy conversion efficiency of the system. In addition to advancing the phase current turn-off angle, the turn-on angle is delayed to improve the drive's performance and increase the efficiency even further. The focus is on sub-fractional horsepower single-phase BLDC motors with bifilar winding which, concerning this matter, have not drawn much attention in the literature yet. The findings of the paper show that the improved switching strategy can reduce current peaks, breaking torques, copper losses, and therefore increase efficiency.