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Safety drive circuit for pump motor

  • US 5,076,761 A
  • Filed: 06/26/1990
  • Issued: 12/31/1991
  • Est. Priority Date: 06/26/1990
  • Status: Expired due to Fees
First Claim
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1. A motor drive circuit for utilizing power from an alternating current source to drive a direct current motor which is mechanically coupled to a liquid pump, comprising:

  • a) a circuit breaker connected to said alternating current source, said circuit breaker having a plurality of circuit disconnecting inputs;

    b) a direct current power supply connected to said circuit breaker and to said motor;

    c) a motor drive circuit connected to said motor, said motor drive circuit having at least two control inputs;

    d) a pressure set circuit connected to one of said at least two control inputs, said pressure set circuit having means for presetting a desired pump output pressure;

    e) a pressure sensing circuit connected to another of said at least two control inputs, said pressure sensing circuit having means for sensing said pump liquid pressure;

    f) means for sensing the current passing into said power supply from said alternating current source, including means for disconnecting said circuit breaker if the sensed current exceeds a predetermined limit;

    g) means for sensing the voltage of said alternating current source, including mean for activating one of said circuit breaker disconnecting inputs if the sensed voltage exceeds a predetermined limit;

    h) means for sensing the current through said motor, including means for activating one of said circuit breaker disconnecting inputs if the sensed current exceeds a predetermined limit;

    i) means connected to said pressure sensing circuit for sensing a predetermined maximum pressure, including means for activating one of said circuit breaker disconnecting inputs if the predetermined maximum pressure is sensed; and

    j) means for sensing the difference between the preset pressure setting and the sensed output pressure and generating a difference signal, and means for comparing this difference signal with a signal representative of motor current, including means for activating one of said circuit breaker disconnecting inputs if the compared signals exceed a predetermined limit.

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