US3857069A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ground fault circuit interrupter and module therefor
Assignee: General Electric Co
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Filing: 1973-12-20
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Granted: 1974-12-24
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Expires: 1993-12-20
Abstract
Abstract A ground fault circuit interrupter (GFCI) utilizes this oscillator operating to induce a first signal in a ground faulted neutral conductor to also inject into the differential current transformer a second signal of opposite polarity to the first. Circuit interruption is initiated when the periodically monitored transformer secondary output voltage is zero or different from zero in a predetermined polarity, indicating either a ground fault on one of the line and neutral conductors or a failure of either the current transformer, the auxiliary transformer, or the oscillator itself, thus providing a measure of fail-safe protection.
Inventors
- 👤 E Howell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 11:06
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/33; H02H3/331; H02H3/16; H02H3/17
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
148 words
A ground fault circuit interrupter comprising, in combination: A. circuit interrupter contacts for connection in the line side of a power distribution circuit including a line conductor and a neutral conductor grounded at the power source; B. means for sensing a current imbalance in the line and neutral conductors and developing an output signal proportional to any such current imbalance; C. a signal source including an auxiliary transformer for inducing a first signal on the neutral conductor effective to produce a current imbalance sensible by said sensing means in the event of a low impedance neutral conductor ground fault; D. means coupling a second signal to said sensing means effective to counteract the imbalancing effect thereon of said first signal; and E. signal processing means for processing said output signal such as to initiate circuit interrupting operation of said interrupter contacts when said output signal is substantially zero.
Claim 2
Dependent Claim
148 words
A ground fault circuit interrupter comprising, in combination: A. circuit interrupter contacts for connection in the line side of a power distribution circuit including a line conductor and a neutral conductor grounded at the power source; B. means for sensing a current imbalance in the line and neutral conductors and developing an output signal proportional to any such current imbalance; C. a signal source including an auxiliary transformer for inducing a first signal on the neutral conductor effective to produce a current imbalance sensible by said sensing means in the event of a low impedance neutral conductor ground fault; D. means coupling a second signal to said sensing means effective to counteract the imbalancing effect thereon of said first signal; and E. signal processing means for processing said output signal such as to initiate circuit interrupting operation of said interrupter contacts when said output signal is substantially zero.
Claim 3
Dependent Claim
33 words
The ground fault circuit interrupter of claim 1, wherein said signal processing means further includes means for also initiating circuit interruption when said output signal is different from zero in a predetermined polarity.
Claim 4
Dependent Claim
45 words
The ground fault circuit Interrupter of claim 2, wherein said sensing means comprises a differential current transformer having first and second primary windings for connection in series with the line and neutral conductors, respectively, and a secondary winding in which said output signal is developed.
Claim 5
Dependent Claim
22 words
The ground fault circuit interrupter of claim 3, wherein said coupling means includes a third primary winding of said differential current transformer.
Claim 6
Dependent Claim
35 words
The ground fault circuit interrupter of claim 4, wherein said coupling means further includes a secondary winding of said auxiliary transformer connected in loop circuit with said third primary winding of said differential current transformer.
Claim 7
Dependent Claim
27 words
The ground fault circuit interrupter defined in claim 2, wherein said signal processing means includes a comparator for comparing said output signal with a predetermined reference signal.
Claim 8
Dependent Claim
35 words
The ground fault circuit interrupter of claim 6, which further includes a gating circuit driven in synchronism with said signal source for periodically enabling said comparator to compare said output signal with said reference signal.
Claim 9
Dependent Claim
45 words
The ground fault circuit interrupter of claim 7, wherein said signal source further includes a signal generator connected to drive said auxiliary transformer and said gating circuit, said gating circuit including means responsive to a failure of said signal generator for continuously enabling said comparator.
Claim 10
Dependent Claim
44 words
The ground fault circuit interrupter defined in claim 6, which further includes: A. an integrator connected to integrate the outputs of said comparator; and B. a threshold detector operable when the integration of said comparator outputs exceeds a predetermined level to initiate circuit interruption.
Claim 11
Dependent Claim
148 words
A module for use in a ground fault circuit interrupter to provide fail-safe operation, said module comprising, in combination: A. means for sensing a current imbalance in the line and neutral conductors of a distribution circuit, the neutral conductor being grounded at the power source, said sensing means developing an output signal proportional to any such current imbalance; B. signal source including an auxiliary transformer for inducing a first signal on the neutral conductor effective to produce a current imbalance sensible by said sensing means in the event of a low impedance neutral conductor ground fault; C. means coupling a second signal to said sensing means effective to counteract the imbalancing effect thereon of said first signal; and D. signal processing means for processing said output signal such as to initiate circuit interruption when said output signal is substantially zero or different from zero in a predetermined polarity.
Claim 12
Dependent Claim
148 words
A module for use in a ground fault circuit interrupter to provide fail-safe operation, said module comprising, in combination: A. means for sensing a current imbalance in the line and neutral conductors of a distribution circuit, the neutral conductor being grounded at the power source, said sensing means developing an output signal proportional to any such current imbalance; B. signal source including an auxiliary transformer for inducing a first signal on the neutral conductor effective to produce a current imbalance sensible by said sensing means in the event of a low impedance neutral conductor ground fault; C. means coupling a second signal to said sensing means effective to counteract the imbalancing effect thereon of said first signal; and D. signal processing means for processing said output signal such as to initiate circuit interruption when said output signal is substantially zero or different from zero in a predetermined polarity.
Claim 13
Dependent Claim
43 words
The module defined in claim 10, wherein said sensing means comprises a differential current transformer having first and second primary windings for connection in series with the line and neutral conductors, respectively, and a secondary winding in which said output signal is developed.
Claim 14
Dependent Claim
32 words
The module defined in claim 11, wherein said coupling means includes a third primary winding on said differential current transformer and a secondary winding of said auxiliary transformer connected in loop circuit.
Claim 15
Dependent Claim
62 words
The module defined in claim 12, wherein said signal processing means includes a comparator for comparing said output signal with a predetermined reference signal, and said module further includes a gating circuit synchronized with said signal source for periodically enabling said comparator to compare said output signal with said reference signal pursuant to developing a comparator output capable of initiating circuit interruption.
Claim 16
Dependent Claim
35 words
The module defined in claim 13, wherein said comparator includes means for referencing the voltage of said output signal to a fixed voltage which exceeds the voltage of said reference signal in said predetermined polarity.
Claim 17
Dependent Claim
56 words
The module defined in claim 13, wherein said signal source further includes a signal generator conNected to drive said auxiliary transformer and said gating circuit, said gating circuit including means for continuously enabling said comparator in the event of a failure of said signal generator, thereby to develop a continuing comparator output for initiating circuit interruption.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-23 | 1978-06-24 | 1978-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-23 | 1982-06-24 | 1982-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-23 | 1986-06-24 | 1986-12-24 | $7700.00 | Window Closed / Lapsed |