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Stall protection circuit for an electronically commutated motor

  • US 5,017,846 A
  • Filed: 04/05/1990
  • Issued: 05/21/1991
  • Est. Priority Date: 04/05/1990
  • Status: Expired due to Fees
First Claim
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1. A control circuit for a system including 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 and having a rotatable assembly associated with the stationary assembly in selective magnetic coupling relation therewith for rotation at a motor speed in response to a magnetic field generated by the winding stages, a commutating circuit for the motor responsive to a control signal for applying the voltage to one or more of the winding stages at a time to commutate the winding stages in a preselected sequence to rotate the rotatable assembly, and tachometer pulse signal generating means for generating a pulsed signal representative of the rotational speed of the rotatable assembly and having a duty cycle, said control circuit comprising:

  • first means for inhibiting application of the motor voltage to the winding stages in response to the tachometer pulse signal when the motor speed is below a preset minimum speed; and

    second means for inhibiting application of the motor voltage to the winding stages in response to the tachometer pulse signal when the duty cycle of the tachometer pulse signal is outside a preselected acceptable range whereby application of the motor voltage to the winding stages is inhibited when the motor is stalling as indicated by the motor speed being below the preset minimum speed or as indicated by the duty cycle of the tachometer pulse signal being outside the preselected acceptable range.

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