PERMANENT MAGNET BRUSHLESS DC MOTOR HAVING REDUCED COGGING

摘要

An improved salient pole configuration for adynamoelectric machine is disclosed, particularly for apermanent magnet brushless DC motor wherein coggingtorque is a problem. One or more apertures or"reluctance holes" are disposed within the head portionof the salient poles in the stator such that thereluctance holes are substantially adjacent but notadjoining the pole face, thereby forming a bridge betweenthe aperture and the pole face. The reluctance holebridge provides a substantially constant air gap fluxdensity to reduce cogging, while at the same time,provides a low reluctance shunt path for the armaturereaction flux around the permanent magnet to improve thedemagnetization margin. The efficiency of the machine isalso improved.