Abstract: Method and apparatus for detecting breakage in a yarn strand being wound onto a yarn support member rotatably driven by a DC motor and having a closed-loop motor control system for maintaining a desired velocity of the motor and for signaling commutation of the phases of the motor during the yarn winding operation. The closed-loop motor control system monitors the signal conduction angles delivered to commutate the phase windings of the motor, detects a sudden minimum preestablished decrease in the monitored conduction angles, and generates a control signal in response to a sudden decrease in the conduction angle resulting from a yarn strand breakage. The control signal may be employed to stop current supply to the motor.

Abstract: Method and apparatus for closed-loop microprocessor control of an electric motor having one or more phase windings and commutation of the phases by rotor/stator position sensors to provide improved efficiency in motor operation wherein the conduction angle of a phase energization of the motor at a given speed of operation is measured, the phase advance adjusted in a positive or negative direction to obtain a subsequent conduction angle, and the two sequential conduction angles compared. Based on the comparison, further phase advance and comparison of sequentially measured conduction angles is carried out, in positive or negative directions of phase advance, to maintain a minimum conduction angle and improve operating efficiency of the motor.

Abstract: A variable reluctance motor having improved means for detecting the relative position of the rotor and stator during rotation of the rotor whereby signals may be employed to commutate the motor, comprising sensed means on the rotor including four sets of elements, each set located within an arcuate length of 90.degree. and each set having two sensed portions with leading edges in the direction of rotation being separated by alternating arcuate lengths of 30.degree. and 60.degree.. Sensing means comprising two sensors arcuately separated by 30.degree. times n wherein n is 1, 2, 4, or 5 are located adjacent the path of rotation of the sensed elements. In a preferred embodiment, the sensed means is a permanent ring magnet having unequal alternating arcuate North and South pole lengths, and the sensing means are two Hall effect sensors. Commutation of a three-phase motor having four rotor poles and six stator poles can thus be effected with the use of only two sensors.