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Digital logic control system for three-phase submersible pump motor

  • US 4,021,700 A
  • Filed: 06/04/1975
  • Issued: 05/03/1977
  • Est. Priority Date: 06/04/1975
  • Status: Expired due to Term
First Claim
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1. A digital logic control system for controlling the coupling of a three-phase AC power supply, having a predetermined power line frequency, to a three-phase submersible pump motor to regulate the operation thereof, comprising:

  • coupling means for coupling the three-phase AC power supply to the submersible pump motor to energize and effect rotation of the motor;

    a clock pulse source, coupled to said AC power supply, for producing precisely timed clock pulses periodically recurring at the power line frequency;

    monitoring means for monitoring the three phase currents drawn by the pump motor from the AC power supply;

    a pulse counting timer coupled to said clock pulse source and, when operable, counting down from a preset starting state to a final state and thereby providing, a predetermined time delay interval;

    means, controlled by said monitoring means and responsive to the detection of an underload condition in which the amplitude level of at least one of the phase currents falls below a preset normal amplitude range, for rendering said pulse counting timer operable thereby to count said clock pulses and advance from its starting state to its final state;

    underload protection means, controlled by said timer and operable at the termination of said predetermined time delay interval when said timer reaches its final state, for interrupting said coupling means to decouple the pump motor from the AC power supply;

    a pulse counting timing device coupled to said clock pulse source and, when operable, counting down from a preset starting state to a final state, and thereby providing, a given time delay interval;

    means, controlled by said monitoring means and responsive to the sensing of an overload condition wherein the amplitude level of at least one of the phase currents exceeds said normal amplitude range, for rendering said pulse counting timing device operable thereby to count said clock pulses and progress from its starting state to its final state;

    overload protection means, controlled by said timing device and operable at the conclusion of said given time delay interval when said timing device reaches its final state, for interrupting said coupling means to decouple the pump motor from the AC power supply;

    a pulse counting timing mechanism coupled to said clock pulse source and, when operable, counting down from a preset starting state to a final state, and thereby providing, a certain time delay interval;

    means controlled by said underload protection means for rendering said timing mechanism operable, when the pump motor has been shutdown due to an underload condition, thereby to count said clock pulses and advance from its starting state to its final state;

    re-enabling means, controlled by said timing mechanism and operable when said certain time delay interval has elapsed after the pump has been shutdown, for automatically reconnecting the AC power supply to the pump motor to effect re-energization thereof;

    and means for inhibiting the operation of said re-enabling means when the shutdown occurs in response to an overload conditon.

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