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Control system for an electronically commutated motor

  • US 4,449,079 A
  • Filed: 08/27/1982
  • Issued: 05/15/1984
  • Est. Priority Date: 04/17/1980
  • Status: Expired due to Term
First Claim
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1. A system for controlling the energization of an electronically commutated motor having a stationary assembly with a plurality of winding stages and also having a rotatable assembly associated in magnetic coupling relation with the stationary assembly upon the energization of the motor, the system comprising:

  • means responsive to the angular position of the rotatable assembly for providing commutation signals;

    a plurality of commutation switching means for connection with the winding stages, respectively;

    means for applying the commutation signals in sequence to said commutation switching means to control the conductivity thereof;

    circuit means for dissipating energy generated by the commutation of the winding stages and including a first common point connected to one terminal of each of the winding stages, and first diode means for separate connection between the other terminal of each of the winding stages and a second common point;

    said commutation switching means being connected between a third common point and the other terminal of each of the winding stages;

    an energy return circuit including capacitor means for connection between said first and second common points;

    first impedance means, first transistor means and second diode means for connection in series combination between said first and second common points;

    voltage divider means and second transistor means for connection in series combination substantially between said second and third common points, said voltage divider means including second and third impedance means for connection at a fourth common point;

    means responsive to the voltage at said fourth common point for controlling the conductivity of said first transistor means;

    means for deriving a control signal representative of the actual angular velocity of the rotatable assembly; and

    means for applying the control signal to said second transistor means to decrease the conductivity thereof whenever the actual angular velocity of the rotatable assembly exceeds an externally determined variable limit with the decreased conductivity of said secnd transistor means being effective to increase the conductivity of said first transistor means and whereby energy generated upon the commutation of the winding stages is stored in said capacitor means for subsequent dissipation and a negtive torque is variably applied to the rotatable assembly in proportion to the amount by which the actual velocity exceeds the variable limit.

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