Commutation torque ripple reduction in a position sensorless brushless DC motor drive

This paper presents a novel method to reduce commutation torque ripple in a position sensorless brushless DC (BLDC) motor drive. To compensate the commutation torque ripple completely, conventional methods should know commutation interval, so that they need current sensors. However, the proposed method measures commutation interval from the terminal voltage of a brushless DC motor, calculates a PWM duty ratio using the measured commutation interval to suppress the commutation torque ripple, and applies to the calculated PWM duty ratio only during the next commutation. Experimental results verify that the proposed method implemented in an air-conditioner compressor controller considerably reduces not only the pulsating currents but also vibrations of a position-sensorless BLDC motor.