Commutation torque ripple of four-switch brushless DC motor drives, part I: analysis

Torque ripple generated in the commutation interval is one of the main drawbacks of BLDC motor. This paper presents an original comprehensive study on the generated torque ripples due to phase commutation in the four-switch, three-phase inverter (FSTPI) brushless dc motor drives 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. The results indicate that because of asymmetrical voltages of phases in a FSTPI brushless dc motor, commutations in six operation modes are different. Also, it is shown that the ripple is independent of current and varies with speed