Patent ID: 6194799
Filing Date: 2001-02-27
Classification: B60L,H02K,Y02T

Abstract:
A direct current (DC) permanent magnet electric motor comprising:a stationary portion including a plurality of C-shaped electromagnets disposed to define an inner annular channel, each of said electromagnets having poles;a rotatable portion including:a shaft rotatable with respect to said stationary portion;at least one disc mounted to said shaft, said disc having an annular portion rotatably disposed within said inner annular channel of said stationary portion; anda plurality of permanent magnets each having a direction of magnetization and poles, said plurality of permanent magnets disposed on said annular portion of said disc so that the direction of magnetization thereof is transverse through said disc and so that the poles thereof are aligned in coupling proximity to the poles of said electromagnets;position circuitry for sensing a position of said plurality of permanent magnets with respect to said plurality of said electromagnets and for providing a signal based on said position of said plurality of electromagnets to cause said rotatable portion to rotate;each of said plurality of electromagnets including a winding;said winding of at least one of said electromagnets having a configuration that demagnetizes said permanent magnets at stall conditions; andelectrical interlocking circuitry for allowing said configuration of said winding of said at least one of said electromagnets to be activated when said shaft reaches a preset speed that reduces current in said windings to a level sufficient to prevent demagnetization of said permanent magnets.