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Manually set ground fault circuit interrupter

  • US 5,418,678 A
  • Filed: 09/02/1993
  • Issued: 05/23/1995
  • Est. Priority Date: 09/02/1993
  • Status: Expired due to Term
First Claim
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1. A ground fault circuit interrupter requiring manual setting following connection to a power source or termination of a power source interruption, comprising:

  • first and second input terminals for connection to the line and neutral terminals, respectively, of an AC power source;

    first and second output terminals for connection to the line and neutral terminals, respectively, of an AC load;

    first and second conductive paths extending, respectively, between said first input terminal and said first output terminal and between said second input terminal and said second output terminal;

    a relay comprising a relay coil and first and second relay contact sets, said first and second relay contact sets being connected in said first and second conductive paths, respectively, in order to selectively connect said input terminals to said output terminals when said contact sets are in a closed position and to selectively disconnect said input terminals from said output terminals when said contact sets are in an open position;

    a relay coil circuit for selectively energizing said relay coil in response to a control signal in order to maintain the first and second relay contact sets in a closed position, and for selectively de-energizing the relay coil in response to the absence of said control signal in order to maintain the first and second relay contact sets in an open position;

    a source for producing said control signal;

    a current sensing circuit for producing a trip signal in response to an imbalance in the current flow through said first and second conductive paths that is indicative of a ground fault condition at an AC load connected to said first and second output terminal;

    a load power sensing circuit coupled to at least one of said first and second output terminals for producing a load power signal when power is being made available at said first and second output terminals;

    a trip circuit connected to said current sensing circuit, said load power sensing circuit and said relay coil circuit for opening and closing said relay contact sets, said trip circuit including an input for receiving said control signal, a controlled switching device responsive to said load power signal for applying said control signal to said relay coil circuit in order to maintain said relay contact sets in a closed position when power is being made available at said first and second output terminals and for removing said control signal from said relay coil circuit in order to open said relay contact sets when power is not being made available at said output terminals, a switching circuit responsive to said trip signal for removing said control signal from said relay coil circuit in order to open said relay contact sets in response to a ground fault condition, and a manual reset switch for restoring said control signal to said relay coil circuit and thereby closing said relay contact sets following termination of a ground fault condition, said manual reset switch also serving as a manual set switch for closing said relay contacts following connection of said ground fault circuit interrupter to an AC power source or following termination of an AC power source interruption.

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