Patent ID: 7276830

Claim:
A motor comprising: a) a stator; b) a rotor mounted for rotation in the stator; c) first and second poles of the stator; d) a winding on at least on of the stator poles; e) at least one pair of salient poles of the rotor; f) an outer back-iron magnetically joining said stator poles; g) an inner back-iron, extending from at least one of said second stator poles around the rotor so that the magnetic field in the rotor between adjacent poles of the rotor is substantially short-circuited by said inner back-iron for a part of the rotation of the rotor; h) an electrical circuit to power the winding to drivingly rotate the rotor; wherein i) the first pole of the stator is a commutating pole having said winding and never substantially short-circuiting the magnetic field through adjacent rotor poles; j) said second pole of the stator is a field connecting pole provided with said inner back iron; k) the rotor is magnetised so that adjacent ones of said rotor poles are oppositely magnetised; l) said electrical circuit is provided with a controller to produce an alternating magnetic field in the commutating pole of the stator to attract each pole of the rotor as it approaches the commutating pole and to repel each pole of the rotor as it moves away from the commutating pole, said field alternating as many times per revolution of the rotor as there are poles of the rotor; whereby m) the rotor is driven by a combination of electromagnetic torque through interaction between the rotor and the commutating pole and reluctance torque through interaction between the rotor and the field-connecting pole.