Optimal commutation of a BLDC motor by utilizing the symmetric terminal voltage

This paper presents a method to determine the improved commutation position of a brushless DC (BLDC) motor in such a way as to generate the symmetric terminal voltages of the nonenergized phase at the beginning and end of the commutation period. If the BLDC motor is energized at the exact commutation position, the terminal voltage of the nonenergized phase at the beginning of commutation is equal to the terminal voltage at the end of commutation, and the waveform of the terminal voltage should be symmetric. This paper also develops a DSP-based sensorless BLDC motor controller to implement the proposed method and to verify its effectiveness experimentally. This research shows that the proposed method improves the performance of a BLDC motor by increasing torque and efficiency.