Low-inertia, high-torque motors

Claim 1

A low inertia high torque stepping motor comprising: an armature and a coaxial stator structure; said armature consisting of a thin-walled cylinder of nonmagnetic material with a plurality of uniformly spaced parallel thin, flat, elongated magnetic bars embedded in the wall of said cylinder; said stator structure comprising two cylindrical arrays of pole pieces disposed interiorly and exteriorly, respectively, of said armature cylinder with the pole faces of the two arrays fixed closely adjacent the inner and outer surfaces of said embedded bars for minimum air gaps; windings in the slots between the pole pieces; a source of alternating current coupled to some of said windings; a source of direct current coupled to the remainder of said windings, said direct current source comprising rectifiers coupled between said alternating current source and the remainder of said windings for changing the alternating current to unidirectional pulses of current in the remainder of said windings; and control circuit means connected to said direct current source for selectively controlling said pulse to rotationally step said armature discrete distances; the windings in which the direct current is flowing being disposed in said slots for superimposing on the alternating field pulses of magnetizing force for selectively aiding and bucking, respectively, the alternating field at different pole pieces.