Shifted pole single phase variable reluctance motor

In a hybrid single-phase variable reluctance motor having a stator with at least two pair of inwardly salient teeth terminating at a central bore, the teeth being arranged in diametrically opposed pairs of teeth which are evenly spaced around said central bore, a phase winding operatively associated with a first pair of said stator teeth and, when energized, causing a temporary magnetization of said one pair of stator teeth, a rotor disposed for rotation in the central bore and having at least one pair of outwardly salient teeth diametrically opposed to each other, a permanent magnet positioned at an end of one tooth of a second pair of said stator teeth, and a rotor position detector disposed at the other stator tooth of said second pair thereof for detecting the rotational position of the rotor in the central bore, the improvement wherein one tooth of said second pair of stator teeth is shifted with respect to a longitudinal axis of said second pair of teeth thereby to eliminate any stable detent position in which the rotor could otherwise stop when the motor is stopped, the torque required to move the rotor when stopped in this position making it difficult to restart the motor.

In a hybrid single-phase variable reluctance motor having a stator with four of inwardly salient teeth terminating at a central bore, the teeth being arranged in diametrically opposed pairs of teeth which are evenly spaced around the central bore, a phase winding operatively associated with a first pair of said stator teeth and, when energized, causing a temporary magnetization of said first pair of stator teeth, a rotor disposed for rotation in the central bore and having at least one pair of outwardly salient teeth diametrically opposed to each other, a permanent magnet positioned at an end of one tooth of a second pair of said stator teeth, and a rotor position detector disposed at the other tooth of said second stator pair for detecting the rotational position of the rotor in the central bore, the improvement wherein one tooth of said second pair of stator teeth is shifted with respect to a longitudinal axis of said second pair of teeth thereby to eliminate any stable detent position in which the rotor could otherwise stop when the motor is stopped, the torque required to more the rotor when stopped in this positioned making it difficult to restart the motor, and the rotor and stator each having more than two poles thereby to reduce the amount of "ovalizing" of a motor frame.