Analysis and Control of Commutation Torque Ripple in Four-Switch, Three-Phase Brushless DC Motor Drive

Torque ripple generated in the commutation interval is one of the main drawbacks of BLDC motor. This paper presents an original study on the generated torque ripples due to phase commutation in the four-switch, three-phase inverter (FSTPI) brushless dc motor drive which are suitable for low cost applications. Torque ripple and commutation duration values are obtained for different operation conditions and problem in high speed region of FSTPI-BLDC is shown. Then a novel current control technique is developed to minimize the commutation torque ripple for entire of speed range. The technique proposed here is based on a strategy that the current slopes of the rising and the decaying phases during the commutation intervals can be equalized by proper duty-ratios in each operation mode.