Torque ripple reduction in single phase brushless DC motors of high magnetic load

In single-phase brushless DC motors with high magnetic load, the typical asymmetric air-gap structure will lead to high cogging torque peaks, which will distort the torque envelope together with the high current peaks commonly found. To get rid of the high torque ripples, the design of the crucial structural factors for the tapered air-gap structure are analyzed, and different drive methods are evaluated based on the field-circuit coupling calculation. One simple drive method is proposed by adding one proper shut-off zone into the driving voltage. The tests show that the performances are improved and noise level is decreased.