Dual-mode ground-fault/leakage-current interrupter (GFCI/LCDI) interrupter and self-test/end-of-life (STEOL)
A dual-mode ground-fault/leakage-current interrupter (GFCI/LCDI) is disclosed. The device uses a single differential sense transformer around line and neutral to detect ground-fault (differential) conditions, and a cord-shield path to detect conductor-to-shield leakage and shield-integrity (open/high-resistance) faults. Shield continuity is supervised by detector-domain circuitry that, upon a fault, drives an isolated trigger coupler (ITC) to a common trip stage (e.g., SCR-latched) that opens the interrupter contacts. An optional grounded-neutral detection load (GNDL) on the load side enables detection of downstream neutral-to-ground bonds without a second transformer eliminating high frequency cross talk. A self-test/end-of-life (STEOL) module injects simulated faults, coordinates with the relay state, and, upon persistent failure, places the device in an end-of-life condition that prevents power delivery. The architecture reduces parts count, improves noise immunity, and unifies trip behavior for both GFCI and LCDI events.
1 . A dual-mode ground-fault and leakage-current interrupter (DMGI) for interrupting current between supply terminals and load terminals via line and neutral conductors, comprising:
switching circuitry operable between a closed state connecting the supply terminals to the load terminals and an open state disconnecting the supply terminals from the load terminals;
series-connected shield conductors surrounding the line and neutral conductors;
a single sense transformer encircling the line and neutral conductors, the single sense transformer producing secondary signals in response to current imbalances;
fault detection circuitry coupled to the single sense transformer and operable to detect both ground fault conditions and conductor-to-shield leakage conditions based on the secondary signals;
shield monitoring circuitry for detecting open or high-resistance conditions in the series-connected shield conductors; and
a first bi-stable electronic latch circuit responsive to the fault detection circuitry and the shield monitoring circuitry to actuate the switching circuitry to the open state.
2 . The DMGI as in claim 1 wherein the shield monitoring circuitry comprises:
a second power supply comprising:
a sense supply, wherein the sense supply is connected to the series-connected shield conductors surrounding the line and neutral conductors;
a sense return;
an open shield (OS) detector coupled to the sense supply via the series-connected shield conductors;
an OS trigger connected to the OS detector;
an isolated trigger coupler (ITC) having an input side and an output side, wherein the ITC input side is connected between the sense supply and the OS trigger and ITC output side is connected between the line conductor and the first bi-stable electronic latch circuit.
3 . The DMGI as in claim 2 wherein the second power supply comprises a bridge rectifier power supply.
4 . The DMGI as in claim 2 wherein the OS detector comprises an npn transistor.
5 . The DMGI as in claim 2 wherein the OS trigger comprises an SCR.
6 . The DMGI as in claim 2 wherein the ITC comprises an optocoupler.
7 . The DMGI as in claim 2 wherein the ITC comprises a micro relay.
8 . The DMGI as in claim 1 further comprising a grounded neutral detection load (GNDL).
9 . The DMGI as in claim 8 wherein the GNDL comprises an LED circuit.
10 . The DMGI as in claim 8 wherein the GNDL comprises a capacitive network circuit.
11 . The DMGI as in claim 1 further comprising:
a self test module, the self test module comprising:
a simulated ground fault generator for simulating a self test ground fault;
a relay synchronized switch connected to the simulated ground fault generator, wherein the relay synchronized switch disables fault detection circuitry during self test;
an auto-monitoring logic module connected to the simulated ground fault generator, wherein the auto-monitoring logic module determines if self test fails; and
an end-of-life switch operable to disconnect the supply terminals from the load terminals upon a self test failure signal from the auto-monitoring logic module.
12 . A dual-mode ground-fault and leakage-current interrupter (DMGI) for interrupting current between supply terminals and load terminals via line and neutral conductors, comprising:
switching circuitry operable between a closed state connecting the supply terminals to the load terminals and an open state disconnecting the supply terminals from the load terminals;
series-connected shield conductors surrounding the line and neutral conductors;
a single differential-current sense transformer encircling the line and neutral conductors and producing a secondary signal representative of current imbalance;
ground-fault detection circuitry coupled to the secondary signal and configured to generate a ground-fault trip signal when a ground-fault criterion is satisfied;
leakage-current detection circuitry configured to detect conductor-to-shield leakage and shield-integrity faults and to generate a leakage trip signal;
shield-monitoring circuitry configured to detect open or high-resistance conditions in the series-connected shield conductors; and
a bi-stable electronic latch circuit operatively coupled to the switching circuitry and configured, in response to either the ground-fault trip signal or the leakage trip signal, to place the switching circuitry in the open state, wherein the bi-stable electronic latch circuit is responsive to the shield-monitoring circuitry.
13 . The DMGI of claim 12 wherein the shield-monitoring circuitry comprises:
a sense supply and a sense return forming a detector-domain power source;
an open-shield (OS) detector coupled to the sense supply through the series-connected shield conductors;
an OS trigger driven by the OS detector; and
an isolated trigger coupler (ITC) having an input side connected between the sense supply and the OS trigger and an output side referenced to a trip/actuation return, the TTC being operative to convey a control state to the bi-stable electronic latch circuit.
14 . The DMGI of claim 13 wherein the ITC comprises an optocoupler.
15 . The DMGI of claim 12 further comprising a grounded-neutral detection load (GNDL) connected across the load-side line and neutral.
16 . The DMGI of claim 15 wherein the GNDL comprises an LED indicator circuit.
17 . A dual-mode ground-fault and leakage-current interrupter (DMGI) for interrupting current between supply terminals and load terminals via line and neutral conductors, comprising:
switching circuitry operable between a closed state connecting the supply terminals to the load terminals and an open state disconnecting the supply terminals from the load terminals;
a single differential-current sense transformer encircling the line and neutral conductors and producing a secondary signal representative of line/neutral current imbalance;
ground-fault detection circuitry coupled to the secondary signal and configured to generate a ground-fault trip signal when a ground-fault criterion is satisfied;
a leakage/continuity detection function associated with a flexible cord set, the function including series-connected shield conductors respectively surrounding the line and neutral conductors and shield-monitoring circuitry configured to detect open or high-resistance shield conditions and/or conductor-to-shield leakage, the shield-monitoring circuitry comprising:
a sense supply and sense return forming a detector-domain power source;
an open-shield (OS) detector coupled to the sense supply through the series-connected shield conductors;
an OS trigger driven by the OS detector, and
an isolated trigger coupler (ITC) having an input side connected between the sense supply and the OS trigger and an output side referenced to a trip/actuation retum, the ITC being operative to convey a control state to a trip stage and thereby provide a leakage trip signal;
a bi-stable electronic latch circuit operatively coupled to the switching circuitry and configured, in response to either the ground-fault trip signal or the leakage trip signal, to place the switching circuitry in the open state;
a grounded-neutral detection load (GNDL) connected across the load-side line and neutral conductors; and
a self-test module comprising:
a simulated ground-fault generator;
a relay-synchronized switch configured to temporarily suppress normal ground-fault detection during self-test;
an auto-monitoring logic module configured to determine whether self-test fails; and
an end-of-life switch operable to disconnect the supply terminals from the load terminals in response to a self-test failure indication.
18 . The DMGI of claim 17 , wherein the grounded-neutral detection load (GNDL) comprises an LED indicator circuit.