US3930187A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ground fault interrupter with means protecting against a grounded neutral condition and with a test circuit for testing performance
Assignee: Westinghouse Electric Corp
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Filing: 1973-11-20
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Granted: 1975-12-30
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Expires: 1993-11-20
Abstract
Abstract In a ground fault interrupter of the differential transformer type having a means for protection against a grounded neutral condition, which means is located on the supply side of the differential transformer, there is provided a test circuit branch connected between a first point on the load side of the differential transformer to the line conductor and on the supply side of the differential transformer to the neutral conductor. This arrangement provides the capability to test performance of the differential transformer and also the means for protection against the grounded neutral condition.
Inventors
- 👤 John J Misencik
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 19:32
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/33; H02H3/331
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
307 words
Ground fault interrupter apparatus comprising: a differential current transformer including a magnetic core, a plurality of primary windings on said core, each being one of the line and neutral conductors of an AC electrical distribution system connected between a supply and at least one load, and a secondary sensing winding on said core for sensing current unbalance between currents in said primary windings, said neutral conductor being grounded at a supply terminal thereof; means responsive to a predetermined sensed signal on said sensing winding to open at least one of said line conductors; grounded neutral protection means responsive to a fault to ground from the neutral conductor on the lOad side of the differential transformer to produce a current imbalance in said differential current transformer, said grounded neutral protection means being associated with the neutral conductor on the supply side of said differential current transformer; test means to test the ability of the apparatus to trip upon occurrence of either line to ground fault conditions or neutral to ground fault conditions, said test means comprising a circuit branch connected from a first point on a line conductor on the load side of said differential current transformer and a second point electrically proximate the neutral conductor on the supply side of said differential current transformer, said circuit branch including a normally open test switch that is closable to cause unbalanced currents in said primary windings; said grounded neutral protection means comprising an additional transformer having a second magnetic core, a primary winding on said second magnetic core connected between the line and neutral conductors, the neutral conductor of the system being a secondary winding on said second core; and said second point to which said test circuit branch is connected is located adjacent said primary winding of said additional transformer on the side thereof opposite the neutral conductor.
Claim 2
Dependent Claim
307 words
Ground fault interrupter apparatus comprising: a differential current transformer including a magnetic core, a plurality of primary windings on said core, each being one of the line and neutral conductors of an AC electrical distribution system connected between a supply and at least one load, and a secondary sensing winding on said core for sensing current unbalance between currents in said primary windings, said neutral conductor being grounded at a supply terminal thereof; means responsive to a predetermined sensed signal on said sensing winding to open at least one of said line conductors; grounded neutral protection means responsive to a fault to ground from the neutral conductor on the lOad side of the differential transformer to produce a current imbalance in said differential current transformer, said grounded neutral protection means being associated with the neutral conductor on the supply side of said differential current transformer; test means to test the ability of the apparatus to trip upon occurrence of either line to ground fault conditions or neutral to ground fault conditions, said test means comprising a circuit branch connected from a first point on a line conductor on the load side of said differential current transformer and a second point electrically proximate the neutral conductor on the supply side of said differential current transformer, said circuit branch including a normally open test switch that is closable to cause unbalanced currents in said primary windings; said grounded neutral protection means comprising an additional transformer having a second magnetic core, a primary winding on said second magnetic core connected between the line and neutral conductors, the neutral conductor of the system being a secondary winding on said second core; and said second point to which said test circuit branch is connected is located adjacent said primary winding of said additional transformer on the side thereof opposite the neutral conductor.
Claim 3
Dependent Claim
38 words
The subject matter of claim 1 wherein: a current limiting resistor is connected in series with said primary winding on said second core on the line side of said second point for connection of said test circuit branch.
Claim 4
Dependent Claim
44 words
The subject matter of claim 1 wherein: said means responsive to a predetermined sensed signal comprises a circuit breaker having a trip coil, and said primary winding connected between the line and neutral conductors is connected to the line conductor through said trip coil.
Claim 5
Dependent Claim
198 words
In ground fault interrupter apparatus of the differential transformer type which includes a means for protection against disablement upon occurrence of a grounded neutral conductor on the load side of the differential transformer, the improvement comprising: said grounded neutral protection means being associated with the neutral conductor on the supply side of the differential transformer and a test circuit branch is connected from a first point on a line conductor on the load side of the differential current transformer to a second point electrically proximate the neutral conductor on the supply side of the differential current transformer and said test circuit branch comprises a normally open test switch that when closed conducts a current through said grounded neutral protection means as well as causing current imbalance in said differential current transformer; said grounded neutral protection means comprising a core through which the neutral conductor passes as a single turn secondary winding, said core having a primary winding that is in an intermediate circuit branch connected between the line and neutral conductors on the supply side of the apparatus, and said second point being located between the primary winding and a current limiting resistor in the intermediate circuit branch.
Claim 6
Dependent Claim
198 words
In ground fault interrupter apparatus of the differential transformer type which includes a means for protection against disablement upon occurrence of a grounded neutral conductor on the load side of the differential transformer, the improvement comprising: said grounded neutral protection means being associated with the neutral conductor on the supply side of the differential transformer and a test circuit branch is connected from a first point on a line conductor on the load side of the differential current transformer to a second point electrically proximate the neutral conductor on the supply side of the differential current transformer and said test circuit branch comprises a normally open test switch that when closed conducts a current through said grounded neutral protection means as well as causing current imbalance in said differential current transformer; said grounded neutral protection means comprising a core through which the neutral conductor passes as a single turn secondary winding, said core having a primary winding that is in an intermediate circuit branch connected between the line and neutral conductors on the supply side of the apparatus, and said second point being located between the primary winding and a current limiting resistor in the intermediate circuit branch.
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) | 1978-12-29 | 1979-06-30 | 1979-12-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-29 | 1983-06-30 | 1983-12-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-29 | 1987-06-30 | 1987-12-30 | $7700.00 | Window Closed / Lapsed |