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Control system, electronically commutated motor system, draft inducer apparatus and method

  • US 5,075,608 A
  • Filed: 02/20/1990
  • Issued: 12/24/1991
  • Est. Priority Date: 06/24/1974
  • Status: Expired due to Term
First Claim
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1. A control system for an electronically commutated motor having a stationary assembly with a plurality of winding stages for carrying a motor current in response to application of a voltage having a magnitude subject to variations, the motor further having a rotatable assembly, and which control system is adapted to receive control pulses having a duty cycle representing a desired operating torque for the motor, the control system for use with a commutating circuit for controlling power switching devices for applying the voltage to one or more of the winding stages at a time having a duty cycle which is a function of a pulsed signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly, the control system comprising:

  • means responsive to the motor current for generating a pulse width modulated (PWM) series of pulses having a pulse repetition rate having a duty cycle which is a function of the duty cycle of the control pulses, the generating means adapted to supply the PMW series of pulses to the commutating circuit as the pulsed signal;

    means for comparing the applied voltage to a reference voltage; and

    means, responsive to the means for comparing, for increasing the duty cycle of the PWM series of pulses as a function of decreases in the applied voltage and for decreasing the duty cycle of the PWM series of pulses as a function of increases in the applied voltage whereby the operating torque of the motor is a function of the duty cycle of the control pulse and is substantially independent of variations in the magnitude of the applied voltage.

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