| 摘要 |
The present invention minimizes variations in torque due to cogging in a permanent magnet brushless electric motor and, among other things, specifies a topology of a rotor and a stator in relation to one another. According to one embodiment, a permanent magnetic motor includes a housing surrounding a stator that in turn surrounds a rotor rotatably mounted to the housing. The stator has a stator cross section including a plurality of uniformly distributed and spaced apart stator poles separated by slots. The stator poles extend radially inward from the inner surface and terminate at an end defined by an inner pole face. Each end is separated from an adjacent end by a distance defined as a stator slot width W. The rotor cross section includes a plurality of spaced apart permanent magnets carried by the shaft and angularly and uniformly distributed about the shaft. The outer most point of the magnet, measured from the axis of rotation, is separated radially from the inner pole faces by a distance defined as a minimum magnetic air gap. According to one aspect of the present invention, a low cogging effect is achieved when the configuration includes a defined ratio of the stator slot width W to air gap G. To achieve this, the defined ratio of the stator slot width W to air gap G is preferably about equal to or lower than 1.66. That is, the ratio of (stator slot width W)/(air gap G) is about equal to or lower than 1.66.
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