Apparatus and method for determining mis-wiring in a ground fault circuit interrupter

• US 20040037018A1
• Filed: 08/23/2002
• Published: 02/26/2004
• Est. Priority Date: 08/23/2002
• Status: Active Grant

• Current Assignee: CHE Il Electric Wiring Devices Co., Ltd.
• Original Assignee: CHE Il Electric Wiring Devices Co., Ltd.
• Inventors: Kim, Byung-Kook
• Granted Patent: US 6,850,394 B2
• Time in Patent Office: Days
• US Class Current: 361/42
• CPC Class Codes: H01R 13/6658 on printed circuit board H01R13/6666 - H01R13/6691 take precedence
• CPC Class Codes: H01R 13/7032 making use of a separate bridging element directly cooperating with the terminals
• CPC Class Codes: H01R 13/7135 with ground fault protector H01R13/7132 takes precedence
• CPC Class Codes: H02H 3/338 also responsive to wiring error, e.g. loss of neutral, break

Abstract

A GFCI mis-wiring detector includes a set of input terminals for an AC source, and a set of output terminals for an AC load. The set of output terminals are conductively connected to the set of input terminals. A GFCI circuit has one or more switches that selectively interrupt the connection between the set of input terminals and the set of output terminals when a ground fault occurs. A mis-wiring detection circuit causes the one or more switches of the GFCI circuit to open when the AC source is electrically coupled to the set of output terminals for a first time interval, even if there is no imbalance in the current flow. Additionally, a suppression circuit suppresses operation of the mis-wiring detection circuit when the AC source is electrically coupled to the input terminals for a second time interval. The second time interval is less than the first time interval.

Claims

1. A ground fault circuit interrupter for an AC electrical receptacle, comprising

first and second input terminals for conductive coupling to the hot and neutral sides, respectively, of an AC line;

first and second output terminals for conductive coupling to the hot and neutral sides, respectively, of at an AC load;

first and second conductive paths electrically connecting, respectively, the first input terminal to the first output terminal, and the second input terminal to the second output terminal;

first and second sets of electrical contacts interposed, respectively, between the first input terminal and the first output terminal on the first conductive path, and between the second input terminal and the second output terminal on the second conductive path, the first and second sets of electrical contacts having an open position that inhibits current flow and a closed position that permits current flow;

a circuit interrupter configured to cause the first and second sets of electrical contacts to open upon receiving an interrupt signal;

a ground fault detection circuit configured to detect an imbalance in current flow between the first and second conductive paths that is indicative of a ground fault condition and, when a ground fault condition is detected, to output an interrupt signal to the circuit interrupter;

a mis-wiring detection circuit configured to output an interrupt signal to the circuit interrupter when the hot and neutral sides of the AC line are conductively coupled to the first and second output terminals, even if there is no imbalance in current flow through the first and second conductive paths; and

a suppression circuit configured to suppress operation of the mis-wiring detection circuit when the hot and neutral sides of the AC line are conductively coupled to the first and second input terminals.

2. The ground fault circuit interrupter of claim 1, wherein the mis-wiring detection circuit outputs the interrupt signal to the circuit interrupter when the hot and neutral sides of the AC line are conductively coupled to the first and second output terminals for a first time interval.

3. The ground fault circuit interrupter of claim 1, wherein the suppression circuit suppresses operation of the mis-wiring detection circuit when the hot and neutral sides of the AC line are conductively coupled to the first and second input terminals for a second time interval, wherein the second time interval is less than the first time interval.

4. The ground fault circuit interrupter of claim 1, wherein the mis-wiring detection circuit is electrically coupled to the first and second output terminals both when the first and second sets of electrical contacts are in the open position and when the first and second sets of electrical contacts are in the closed position.

5. The ground fault circuit interrupter of claim 1, wherein the mis-wiring detection circuit outputs an interrupt signal to the circuit interrupter when the AC line is mistakenly conductively coupled to the output terminals, after the first and second sets of electrical contacts have transitioned from the open position to the closed position.

6. The ground fault circuit interrupter of claim 1, further comprising a mis-wiring notification mechanism for providing notification that a mis-wiring has occurred when the mis-wiring detection circuit outputs an interrupt signal and the circuit interrupter causes the first and second sets of electrical contacts to open.

7. The ground fault circuit interrupter of claim 6, wherein the mis-wiring notification mechanism is a reset switch mechanically interconnected to the first and second sets of electrical contacts, and further wherein the notification of a mis-wiring occurs when the reset switch moves into a position indicative of a fault and cannot be reset.

8. The ground fault circuit interrupter of claim 1, further comprising a manual reset switch connected to the first and second sets of electrical contacts, the reset switch for selectively closing the first and second sets of electrical contacts after they have been opened by the circuit interrupter upon receiving an interrupt signal.

9. The ground fault circuit interrupter of claim 8, wherein the reset switch cannot close the first and second sets of electrical contacts for a substantial length of time while a mis-wiring exists.

10. The ground fault circuit interrupter of claim 1, further comprising a test switch for selectively electrically connecting the first conductive path to the second conductive path in a manner that results in a current imbalance indicative of a ground fault condition in order to test proper operation of the ground fault circuit interrupter.

11. A ground fault circuit interrupter (GFCI) mis-wiring detector, comprising:

a GFCI comprising;

a set of input terminals for an AC source;

a set of output terminals for one or more AC loads;

an electrical interconnection between the set of input terminals and the set of output terminals;

a set of switches interposed between the set of input terminals and the set of output terminals on the electrical interconnection for selectively interrupting the electrical interconnection, a portion of the electrical interconnection extending between the set of input terminals and the set of switches, and another portion of the electrical interconnection extending between the set of switches and the set of output terminals;

a ground fault detection circuit to detect a ground fault condition at one or more of the one or more AC loads;

a switch actuator to open the set of switches when a ground fault is detected;

a mis-wiring detection circuit configured to cause the switch actuator to open the set of switches when the AC source is mis-wired to the set of output terminals, even if there is no ground fault detected; and

a set of mis-wiring detection circuit contacts electrically coupling the mis-wiring detection circuit to a set of output nodes, the set of output nodes including the set of output terminals and the portion of the electrical interconnection between the set of switches and the set of output terminals.

12. The GFCI mis-wiring detector of claim 11, further comprising:

a suppression circuit electrically coupled to a set of input nodes, the set of input nodes including the set of input terminals and the portion of the electrical interconnection between the set of input terminals and the set of switches, the suppression circuit configured to suppress operation of the mis-wiring detection circuit when the AC source is correctly wired to the set of input terminals.

13. The GFCI mis-wiring detector of claim 12, wherein the mis-wiring detection circuit causes the switch actuator to open the set of switches when the AC source is mis-wired to the set of output terminals after a first time interval, and further where in the suppression circuit suppresses operation of the mis-wiring detection circuit when the AC source is correctly wired to the set of input terminals after a second time interval, the second time interval being shorter than the first time interval.

14. The GFCI mis-wiring detector of claim 12, wherein the mis-wiring detection circuit and the suppression circuit are communicatively coupled but electrically isolated when the set of switches are open.

15. The GFCI mis-wiring detector of claim 14, wherein the electrical isolation and communicative coupling between the mis-wiring detection circuit and the suppression circuit are achieved using an opto-isolator.

16. The GFCI mis-wiring detector of claim 11, further comprising a mis-wiring notification mechanism for providing notification that a mis-wiring has occurred when the mis-wiring detection circuit has caused the switch actuator to open the set of switches.

17. A ground fault circuit interrupter (GFCI) mis-wiring detector, comprising:

a set of input terminals for an AC source;

a set of output terminals for an AC load, the set of output terminals conductively connected to the set of input terminals;

a GFCI circuit including one or more switches for selectively interrupting the connection between the set of input terminals and the set of output terminals when a ground fault occurs;

a mis-wiring detection circuit for causing the one or more switches of the GFCI circuit to open when the AC source is electrically coupled to the set of output terminals for a first time interval, even if there is no imbalance in the current flow; and

a suppression circuit for suppressing operation of the mis-wiring detection circuit when the AC source is electrically coupled to the input terminals for a second time interval, the second time interval being less than the first time interval.

18. The GFCI mis-wiring detector of claim 17, wherein the mis-wiring detection circuit is electrically coupled to the set of output terminals, even when the switches have interrupted the connection between the set of input terminals and the set of output terminals.

19. The GFCI mis-wiring detector of claim 17, wherein the suppression circuit is electrically coupled to the set of input terminals.

20. The GFCI mis-wiring detector of claim 17, wherein the mis-wiring detection circuit includes a first charging circuit, the time constant of the charging circuit at least partially affecting the first time interval.

21. The GFCI mis-wiring detector of claim 17, wherein the suppression circuit includes a second charging circuit, the time constant of the charging circuit at least partially affecting the second time interval.

22. The GFCI mis-wiring detector of claim 17, wherein the mis-wiring detection circuit and the suppression circuit are communicatively coupled but electrically isolated from each other when the one or more switches are open.

23. The GFCI mis-wiring detector of claim 22, wherein the electrical isolation and communicative coupling between the mis-wiring detection circuit and the suppression circuit are achieved using an opto-isolator.

24. The GFCI mis-wiring detector of claim 17, further comprising a mis-wiring notification mechanism for providing notification that a mis-wiring has occurred when the mis-wiring detection circuit causes the one or more switches of the GFCI circuit to open.

25. An integral AC receptacle and ground fault circuit interrupter (GFCI) for protecting the receptacle, comprising:

a housing;

a plurality of receptacle outlets mounted within the housing, each receptacle for receiving an AC cord plug from an AC load;

a set of output terminals for optionally connecting the AC receptacle in parallel with a remote AC receptacle for which ground fault protection is desired;

an electrical backplane adjacent to the housing for electrically interconnecting the plurality of receptacle outlets and the set of output terminals;

a set of input terminals for connecting to an AC source;

a GFCI circuit, interposed between the set of input terminals and the electrical backplane, the GFCI circuit establishing an interruptable electrical connection therebetween, the GFCI circuit including;

a set of switches for interrupting the electrical connection between the set of input terminals and the electrical backplane;

a solenoid for actuating the set of switches and thereby selectively interrupting the electrical connection between the set of input terminals and the electrical backplane;

at least one detector for sensing an imbalance in current flow between hot and neutral sides through the AC receptacle that is indicative of a ground fault;

a ground fault detection chip that, based on the imbalance in current flow sensed by the at least one detector outputs a SCR-triggering signal;

a SCR for controlling operation of the solenoid that, upon receipt of the SCR-triggering signal from the ground fault detection chip, causes the solenoid to energize; and

a rectifier for providing power to the GFCI circuit;

a GFCI wiring detector, the detector comprising;

an opto-isolator including a phototransistor and a LED;

a long-delay circuit electrically coupled to the LED of the opto-isolator, and to the electrical connection between the set of switches and the output terminals, the long-delay circuit including a charging circuit that begins charging when the AC source is electrically connected to the set of output terminals and, after a first time interval, actuates the phototransistor of the opto-isolator, causing;

the ground fault detection chip to output a SCR-triggering signal, even if there is no imbalance in current flow;

the SCR to trigger;

the solenoid to energize;

the set of switches to be actuated; and

the electrical connection to be interrupted in response to the mis-wiring;

a short-delay circuit electrically coupled to the phototransistor of the opto-isolator, and to the electrical connection between the set of switches and the input terminals, the short-delay circuit including a charging circuit that begins charging when the AC source is electrically connected to the set of input terminals and, after a second time interval, causes operation of the long-delay circuit to be suppressed by;

actuating a shunt-to-ground transistor; and

correspondingly, providing a circuit ground input to the phototransistor;

wherein the second time interval is shorter than the first time interval.

26. The integral AC receptacle and GFCI of claim 25, further comprising a manual reset switch connected to the set of switches of the GFCI circuit, and further wherein notification of a mis-wiring occurs when the manual reset switch trips and cannot be reset.

27. The integral AC receptacle and GFCI of claim 25, wherein the charging circuit of the long-delay circuit and the charging circuit of the short-delay circuit begin charging even if there is no AC load connected to the receptacle and no current flow through the hot and neutral sides of the AC receptacle.

28. A ground fault circuit interrupter (GFCI) mis-wiring detector, comprising:

a GFCI comprising;

input connection means for electrically connecting the GFCI to an AC source;

output connection means for electrically connecting the GFCI to one or more AC loads;

ground fault circuit interrupter means including;

an electrical interconnection conductively coupling the input connection means and the output connection means;

switching means interposed between the input connection means and the output connection means on the electrical interconnection for selectively interrupting the electrical interconnection, a portion of the electrical interconnection extending between the input connection means and the switching means, and another portion of the electrical interconnection extending between the switching means and the output connection means.

ground fault detection means for detecting an imbalance in current flow between the input connection means and the output connection means indicative of a ground fault condition at one or more of the one or more AC loads;

switching control means for opening the switching means in response to the detection of a ground fault condition;

mis-wiring detection means for causing the switching control means to open the switching means when the AC source is electrically connected to the output connection means, even if there is no detected ground fault condition; and

mis-wiring detection contact means electrically coupling the mis-wiring detection means to a set of output nodes, the set of output nodes comprising the output connection means and the portion of the electrical interconnection extending between the switching means and the output connection means.

29. The GFCI mis-wiring detector of claim 28, further comprising:

suppression means electrically connected to a set of input nodes, the set of input nodes comprising the input connection means and the portion of the electrical interconnection extending between the switching means and the input connection means, the suppression means for suppressing operation of the mis-wiring detection means when the AC source is electrically connected to the input connection means.

30. The GFCI mis-wiring detector of claim 29, wherein the mis-wiring detection means causes the switching control means to open the switching means when the AC source is mis-wired to the output connection means after a first time interval, and further where in the suppression means suppresses operation of the mis-wiring detection means when the AC source is correctly wired to the input connection means after a second time interval, the second time interval being shorter than the first time interval.

31. The GFCI mis-wiring detector of claim 28, wherein the mis-wiring detection means and the suppression means are communicatively coupled but electrically isolated when the switching means are open.

32. The GFCI mis-wiring detector of claim 28, further comprising a mis-wiring notification means for providing notification that a mis-wiring has occurred when the mis-wiring detection means has caused the switching control means to open the switching means.

33. A method of detecting a mis-wiring of a ground fault circuit interrupter (GFCI), the the GFCI including a set of input terminals for electrical connection to an AC source and a set of output terminals for electrical connection to an AC load, and the GFCI further including a detector for detecting a ground fault condition and a set of switches that when closed permit an electrical current to flow between the set of input terminals and the set of output terminals, and when open prevents the flow of the electrical current between the sets of input terminals and the set of output terminals, the method comprising:

attaching the AC source to a set of terminals selected from a group consisting of the set of output terminals and the set of input terminals;

closing the set of switches to apply the AC source to both a mis-wiring detection circuit and a suppression circuit;

generating an interrupt signal output from the mis-wiring detection circuit after the AC source has been electrically connected to the set of outputs for a first time interval, the interrupt signal opening the set of switches;

generating a suppression signal output from the suppression circuit after the AC source has been electrically connected to the set of inputs for a second time interval, wherein the second time interval is shorter than the first time interval, the suppression signal suppressing the interrupt signal; and

detecting a mis-wiring of the AC source to the input terminals by opening the set of switches in response to an unsuppressed interrupt signal that is generated before the second time interval elapses and a suppression signal is generated, and that is caused by the mis-wiring detection circuit remaining connected to the AC source when the set of switches is open.