Importance

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Abstract

A single phase permanent magnet motor includes a rotor, a stator, and a quadrature axis winding positioned out-of-phase from a main winding of the stator for generating an output signal representative of rotor angular position. An integrator can be coupled to the quadrature axis winding for phase retarding the output signal, and a comparator can be coupled to the integrator for detecting zero crossings of the phase retarded output signal to provide a commutation signal. The quadrature axis winding can be positioned about ninety electrical degrees out-of-phase from the main winding of the stator, and the integrator can be adapted to phase retard the output signal by a number of degrees which decreases as a speed of the motor increases. At low speeds the phase retard is preferably at about ninety degrees so that the phase retarded signal becomes in-phase with the main stator winding back EMF voltage. The motor may further include a rectifier coupled to the quadrature axis winding for rectifying the output signal, and a lowpass filter for filtering the rectified output signal to provide a signal proportional to velocity. Also the single phase motor is commutated for maximum torque production.

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