Emerson Electric Company

David E Gee

J Stephen Thorn

A control system for a multi-phase brushless permanent magnet motor has circuitry for periodically generating signals representing the relative position of the rotor with respect to the stator, circuitry for decoding the periodically generated signals to determine the presence of the rotor at one of a plurality of predetermined rotary positions with respect to the stator, and circuitry for generating an interrupt signal in response to the presence of the rotor at one of the plurality of predetermined rotary positions with respect to the stator. Electrically controllable switches are connected to the phase windings to control the flow of current therethrough. A microprocessor is responsive to the interrupt signal for controlling in a closed loop manner the switches to commutate the phase windings of the motor a predetermined time after receipt of the interrupt signal. The microprocessor is also responsive to the speed of the motor to start the motor in a open loop mode and to shift commutation to the closed loop mode once the motor reaches a predetermined speed.

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Florissant, MO, United States of America

David E Gee