Cogging Torque Minimization on a Mass-Produced Sub-Fractional Horsepower Brushless Direct Current Claw-Pole Motor

摘要

In mass-produced sub-fractional horsepower brushless direct current drive applications, suboptimal motor behavior, e.g., high cogging torque and as a result high output torque ripple, is often accepted when low-cost yet properly functioning products can be obtained. This paper systematically shows how to minimize the inherently high cogging torque of the low-cost four-pole four-slot single-phase outer rotor claw-pole motor topology, opposed to conventional cogging torque reduction methods, with no increase in manufacturing cost. First, the selected introduction of auxiliary slots can double the cogging torque fundamental frequency, which halves the optimal skewing angle. Second, owing to the doubled cogging torque fundamental frequency, implementing stator claw skewing is much more efficient and can reduce the cogging torque peak values significantly. Proposed is an innovative claw-pole motor design, where the cogging torque reduction methods can be considered at the stage of punching and deep-drawing the steel sheets, at no additional cost. The findings show that, compared with the conventional design, the cogging torque peak-to-peak values have been successfully reduced by 65 % in the simulations and by 67 % in the experiments.