Low-cost sub-fractional horsepower brushless direct current claw-pole machine topology for fan applications

摘要

As to mass-produced sub-fractional horsepower (hp) drives, non-optimal motor behavior is often accepted when cost can be reduced, provided that reliability is not compromised. This paper proposes a brushless direct current (BLDC) claw-pole motor design for a sub-fractional hp fan drive, improving motor behavior twofold: 1) reducing cogging torque ripple and 2) realizing a preferred rotational direction, with no increase in manufacturing cost. Dimensions are so small that specially shaped steel sheets can be used for the stator instead of injection molded parts. The proposed measures are considered at the stage of punching the stator steel sheets and subsequent deep drawing thereof to yield the desired claw shapes and stator yoke. The findings show that the proposed measures (skewing and air gap asymmetry) can significantly reduce the cogging torque and the total torque ripple and prevent the motor from friction-related standstill with no increase in manufacturing cost.