Ground fault circuit interrupter

• US 20030189804A1
• Filed: 04/04/2002
• Published: 10/09/2003
• Est. Priority Date: 04/04/2002
• Status: Active Grant

• Current Assignee: Power Electronics & Systems, Inc.
• Original Assignee: Power Electronics & Systems, Inc.
• Inventors: Kampmeyer, Roy A.
• Granted Patent: US 6,804,094 B2
• Time in Patent Office: Days
• US Class Current: 361/42
• CPC Class Codes: H01H 83/04 with testing means for indicating the ability of the switch or relay to function properly
• CPC Class Codes: H02H 3/05 with means for increasing reliability, e.g. redundancy arrangements for logic circuits H03K19/003
• CPC Class Codes: H02H 3/33 using summation current transformers H02H3/347 takes precedence

Abstract

A ground fault circuit interrupter for use on a circuit having an AC power source electrically connected to a load circuit via hot and neutral lines. The ground fault circuit interrupter having at least a pair of switching components forming part of the circuit for opening the circuit upon occurrence of a ground fault. The switching components are electronic semiconductors, preferably MOSFETs, which permit substantially instantaneous switching. In addition, preferably the ground fault circuit interrupter includes a pair of redundant switching channels so that failure of any one component does not prevent the ground fault circuit interrupter from properly opening the circuit upon detection of a ground fault.

Claims

1. A ground fault circuit interrupter for use on a circuit including an AC power source and a load electrically connected via hot and neutral lines, comprising a switching component forming part of the circuit for opening the circuit upon occurrence of a ground fault, said switching component being an electronic semiconductor which permits substantially instantaneous switching.

2. A ground fault circuit interrupter according to claim 1, wherein said electronic semiconductor is a MOSFET.

3. A ground fault circuit interrupter according to claim 2, wherein said interrupter includes a pair of MOSFET switching components, wherein said pair comprises a single channel of said interrupter, and wherein each of said MOSFET switching components of said pair forms a part of the circuit on the hot line of the circuit.

4. A ground fault circuit interrupter according to claim 3, wherein said interrupter includes a pair of identical and redundant channels.

5. A ground fault circuit interrupter according to claim 3, wherein a first of said pair of said MOSFET switching components is connected in series across its drain and source to the hot line of the circuit, and wherein a second of said pair of said MOSFET switching components is connected across its drain and source adjacent and in series with said first MOSFET switching component in the hot line of the circuit.

6. A ground fault circuit interrupter according to claim 5, wherein said sources of said pair of MOSFET switching components are disposed such that they face each other.

7. A ground fault circuit interrupter according to claim 6, wherein each of said MOSFET switching components has a diode connected across its drain and source, whereby, during a normal non-fault condition, current flows in a path from drain to source through one of said pair of MOSFET switching components while current flows in a path from source to drain of said opposite MOSFET switching component through its diode, and during a ground fault condition, both MOSFET switching components prevent any flow of current through the drain to source paths.

8. A ground fault circuit interrupter according to claim 7, wherein said diodes are disposed back to back so that current flowing in a given direction on the hot line is blocked from passing through one of said diodes and is permitted to flow through the other of said diodes.

9. A ground fault circuit interrupter according to claim 2, wherein said MOSFET switching element of said interrupter opens the circuit to clear a ground fault within 16 milliseconds after initial occurrence of the ground fault and within one single AC fault current sine wave length of a 60 Hz sine wave.

10. A ground fault circuit interrupter according to claim 9, wherein said MOSFET switching element of said interrupter opens the circuit to clear a ground fault within 8 milliseconds after initial occurrence of the ground fault and within a half of one single AC fault current sine wave length of a 60 Hz sine wave.

11. A ground fault circuit interrupter according to claim 4, wherein each channel includes an amplifier for amplifying an AC ground fault current signal, a rectifier for full wave rectifying said AC ground fault current signal after it has been amplified, and a comparator for comparing said amplified and rectified AC ground fault current signal to a preset ground fault threshold level to determine whether a ground fault exists on the circuit.

12. A ground fault circuit interrupter according to claim 11, further comprising a pair of redundant ground fault current sensors each for independently generating said AC ground fault current signal according to ground fault current flowing through the circuit, wherein one sensor transmits its generated signal to one of said channels of said interrupter and the other sensor transmits its generated signal to the other of said channels of said interrupter.

13. A ground fault circuit interrupter according to claim 11, wherein each channel includes a separate driver for each of said MOSFET switching elements, and wherein said drivers interconnect to the gates of said MOSFET switching elements and to said comparator, whereby, when a shutdown signal is received from said comparator indicating the presence of a ground fault, said drivers place the MOSFET switching elements in an off condition in which no current in any of said MOSFET switching elements is permitted to flow from drain to source.

14. A ground fault circuit interrupter according to claim 13, further comprising an overcurrent detector for sensing load current on the hot line, for comparing the current relative to an overcurrent threshold value of said interrupter, and for transmitting a shutdown signal to said drivers.

15. A ground fault circuit interrupter according to claim 12, further comprising a test circuit for simulating a ground fault relative to said sensors to test the operation of said interrupter.

16. A ground fault circuit interrupter for protecting a circuit including an AC power source and a load electrically connected via hot and neutral lines, wherein the improvement comprising:

a channel having a pair of MOSFET switching components forming part of the circuit for opening the circuit upon occurrence of a ground fault, each of said pair of MOSFET switching components being connected in series across its drain and source to the hot line of the circuit, and said sources of said pair of MOSFET switching components being adjacent and disposed back to back; and

each of said MOSFET switching components having a diode connected across its drain and source, and said diodes being disposed in a back-to-back relation;

whereby, during a normal non-fault condition, current flows in a path from drain to source through one of said pair of MOSFET switching components while current flows in a path from source to drain of said opposite MOSFET switching component through its diode, and during a ground fault condition, both MOSFET switching components are placed in an off condition and prevent any flow of current through the drain to source paths.

17. A ground fault circuit interrupter according to claim 16, wherein said interrupter includes a pair of identical and redundant channels.

18. A method of providing ground fault protection to a circuit including an AC power source and a load electrically connected via hot and neutral lines, comprising the steps of:

electrically connecting each of a pair of MOSFETs in series across its drain and source to the hot line of the circuit, said sources of said pair of MOSFETs being disposed back to back, each of said MOSFETs having a diode connected across its drain and source, and said diodes being disposed in a back-to-back relation;

during a normal non-ground fault operating condition, permitting current to flow in a path from drain to source through one of said pair of MOSFETs while permitting current to flow in a path from source to drain of said opposite MOSFET via its diode; and

when a ground fault is detected, substantially instantaneously driving both MOSFETs into an off condition to prevent any flow of current within the MOSFETs through the drain to source paths.

19. A method according to claim 18, wherein said MOSFETs clear a ground fault within 16 milliseconds after initial occurrence of the ground fault and within one single AC fault current sine wave length of a 60 Hz sine wave.

20. A method according to claim 19, further comprising the steps of:

sensing for a differential in current flowing through the hot and neutral lines;

generating an AC ground fault current signal corresponding to said differential sensed during said sensing step;

amplifying said AC ground fault current signal;

full wave rectifying said AC ground fault current signal;

comparing said AC ground fault current signal, after said amplifying and rectifying steps, to a preset stored ground fault threshold level to determine whether a ground fault exists on the circuit; and

sending a shutdown signal to drivers of said pair of MOSFETs when a ground fault is detected, to place the MOSFETs in a non-conducting off condition.