| 摘要 |
To reduce even instantaneous torque variations when pole gaps of a rotor pass stator pole gaps, the stator pole shoes, adjacent the tip, are shaped to provide an air gap (19) which, behind a projecting tip (FIG. 4: 61) first increases to an intermediate value (53) and then decreases to a minimum (50, 50B) over a zone (54) adjacent the pole gap (44A, 44B) which extends, preferably, over about 7 DEG to 20 DEG -el. Preferably, the opposite pole tip (51A) likewise has a projecting end (61A) with an air gap increasing to a maximum (52) and then decreasing essentially monotonically over the major portion of the pole shoe (41) to the minimum (50) close to the other pole tip (51), the maximum air gap (52) being offset about 10 DEG -20 DEG -el from the actual end of the pole tip (51A). Preferably, the pole gaps (17) on the permanent magnet rotor are narrow and skewed over an extent at least as wide as the stator pole gaps (44), for example between 20 DEG to 45 DEG . |
