Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Reexamination Certificate
2001-11-07
2003-11-11
Vu, Bao Q. (Department: 2838)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
C361S042000, C361S045000
Reexamination Certificate
active
06646839
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved surge suppressor which combines a ground fault circuit interrupter with overvoltage protection for AC power lines. The surge suppressor includes a switchable device for disconnecting power from the ground fault circuit interrupter in the event the AC neutral is lost.
2. Discussion Of The Related Art
Apparatus which combine a ground fault circuit interrupter (“GFCI”) with AC overvoltage protection are known. One such apparatus is shown in U.S. Pat. No. 5,654,857 and U.S. Pat. No. 5,841,615, both issued to Bernard Gershen. These patents disclose a GFCI in combination with MOVs connected between the AC line and the AC neutral, between the AC line and ground and between the AC neutral and ground. Another such apparatus is shown in U.S. Pat. No. 6,212,048 B1 issued to Nisar A. Chaudhry, which discloses a GFCI in combination with overvoltage protection between the AC line and the AC neutral and which provides overvoltage protection for electrical equipment without using a separate ground conductor. Instead, a “virtual ground” circuit is employed which simulates the ground conductor. None of the apparatus disclosed in these patents deals with the loss of the AC neutral, which can occur if the neutral bar at the service entrance corrodes, something which occurs not infrequently in salt air environments.
SUMMARY OF THE INVENTION
The present invention combines a GFCI with AC overvoltage protection and also uses a switchable device to disconnect the power from the GFCI in the event the AC neutral is lost. The preferred embodiments employ a relay with the coil connected between the AC line and the AC neutral. The AC line and the AC neutral are connected to a set of input relay contacts. The GFCI is connected to the AC line and the AC neutral through a set of output relay contacts. Under normal operating conditions the relay is energized and power flows through the relay to the GFCI via the relay contacts. If the AC neutral is lost, the relay is deenergized and the contacts open, thereby disconnecting power from the GFCI. The GFCI preferably has one or more AC outlets for receiving three-prong AC plugs.
The subject matter which I regard as my invention is more particularly pointed out in the claims at the end of the specification. The invention, including its method of operation and its numerous advantages, may best be understood by reference to the following description taken in conjunction with the accompanying drawings wherein like numerals refer to like components.
REFERENCES:
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patent: 5600524 (1997-02-01), Neiger et al.
patent: 5654857 (1997-08-01), Gershen
patent: 5825599 (1998-10-01), Rosenbaum
patent: 5841615 (1998-11-01), Gershen
patent: 5943199 (1999-08-01), Aromin
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patent: 6118639 (2000-09-01), Goldstein
patent: 6122155 (2000-09-01), Aromin et al.
patent: 6212048 (2001-04-01), Chaudhry
Chaudhry Nisar A.
Roach Alfred J.
Morgan & Finnegan L.L.P.
TII Industries Inc.
Vu Bao Q.
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