ROTARY PERMANENT MAGNET ELECTRIC MOTOR HAVING STATOR POLE SHOES OF VARYING DIMENSIONS

摘要

Rotary permanent magnet motors have salient stator poles with non-uniform po le thickness in the radial direction for compensating effects of cogging torque . Pole base portions terminate at pole shoes at the radial air gap. The pole shoes extend in the circumferential direction from the bulkier base portions . Variation of the thickness of the pole shoe changes the concentration of the effective flux at the point of coupling between the stator poles and the permanent magnet pole shoes. As there is no change in the active interfacing area of the pole shoes a uniform air gap is maintained. The torque signature for each stator pole/rotor permanent magnet interface can be selectively changed to smooth motor operation by configuring the stator pole shoe thickness to vary along its circumferential extent as appropriate. Pole shoe s may have tapered leading or trailing edges with respect to a pole base to change the effective flux density in the air gap at a specific pitch of rotation. Additionally, the pole shoe may be shifted off center with respect to the pole base.