Patent US3671809A successfully refreshed from Google Patents.
US3671809A
Expired / Lapsed
US
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Ground fault detector including magnetic amplifier bridge means
Assignee: GTE Sylvania Inc
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Filing: 1971-11-01
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Granted: 1972-06-20
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Expires: 1991-11-01
Abstract
Abstract A protective device for detecting abnormal leakage current to ground in an electrical circuit energized through two or more conductors connected to an AC source, one of the conductors being grounded at the source. The device comprises a magnetic amplifier having a pair of reactor cores upon which a plurality of gate windings are arranged to form a balanced inductance bridge. An oscillator is connected across the bridge to apply a carrier signal at a frequency many times higher than the frequency of the AC source, and the bridge output is connected through a peak detector and amplifier to drive the solenoid of a circuit breaker. Each supply line conductor of the monitored circuit is wound about both the reactor cores with the sense of each windings being arranged to provide a net magnetic flux of zero when equal currents are flowing through each conductor. In this manner the magnetic amplifier provides at the bridge output a null signal during normal current conditions and an error signal voltage in the presence of a current imbalance between the conductors.
Inventors
- 👤 John T Ryan
- 👤 Jeffrey D Ingalls
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 08:19
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/33
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
215 words
Means for detecting a current imbalance between a plurality of electrical conductors having respective input terminals for connection to a source of AC power and respective output terminals for connection to a load, said detecting means comprising, in combination, core means of magnetically permeable material, a plurality of windings on said core means arranged to form a balanced inductance bridge, each of said conductors passing through two portions of said core means so as to provide control windings on both of said core portions, the sense of each of said control windings being arranged so that when the same current flows through each of said conductors the total magnetomotive force produced in said core means is balanced out so that the net magnetic flux in the core means is approximately zero, said balanced inductance bridge having a pair of input terminals and a pair of output terminals, and an oscillator connected across the input terminals of said bridge, said oscillator having a frequency of operation substantially higher than the frequency of said AC source, and said detecting means being operative to provide at said bridge output terminals a null signal when the same current flows through each of said conductors and an error signal voltage in the presence of a current imbalance between said conductors.
Claim 2
Dependent Claim
215 words
Means for detecting a current imbalance between a plurality of electrical conductors having respective input terminals for connection to a source of AC power and respective output terminals for connection to a load, said detecting means comprising, in combination, core means of magnetically permeable material, a plurality of windings on said core means arranged to form a balanced inductance bridge, each of said conductors passing through two portions of said core means so as to provide control windings on both of said core portions, the sense of each of said control windings being arranged so that when the same current flows through each of said conductors the total magnetomotive force produced in said core means is balanced out so that the net magnetic flux in the core means is approximately zero, said balanced inductance bridge having a pair of input terminals and a pair of output terminals, and an oscillator connected across the input terminals of said bridge, said oscillator having a frequency of operation substantially higher than the frequency of said AC source, and said detecting means being operative to provide at said bridge output terminals a null signal when the same current flows through each of said conductors and an error signal voltage in the presence of a current imbalance between said conductors.
Claim 3
Dependent Claim
33 words
Detecting means according to claim 1 further including means coupled to the output terminals of said bridge for responding to a predetermined voltage thereacross and thereby indicating a current imbalance between said conductors.
Claim 4
Dependent Claim
29 words
Detecting means according to claim 1 wherein said core means forms two saturable reactor cores, and each of said conductors provides control windings on both of said reactor cores.
Claim 5
Dependent Claim
79 words
Detecting means according to claim 3 wherein said core means, said bridge windings and said control windings comprise a magnetic amplifier, said bridge windings are the gate windings of said magnetic amplifier, and in the presence of a current imbalance between said conductors the output of said oscillator functions as a carrier and the unbalanced currents through said control windings function as a modulating signal to provide a modulated error signal voltage at the output terminals of said bridge.
Claim 6
Dependent Claim
20 words
Detecting means according to claim 4 further including a voltage peak detector coupled to the output terminals of said bridge.
Claim 7
Dependent Claim
119 words
Detecting means according to claim 4 wherein the windings forming said inductance bridge comprise first, second, third and fourth gate windings each having approximately the same number of turns, said first and fourth gate windings are wound on one of said reactor cores, said second and third gate windings are wound on the other of said reactor cores, said first and second gate windings are serially connected in the same sense across said bridge input terminals, said third and fourth gate windings are serially connected in the same sense across said bridge input terminals, and said bridge output terminals comprise the junction of said first and second gate windings and the junction of said third and fourth gate windings.
Claim 8
Dependent Claim
60 words
The combination of claim 1 wherein said detecting means comprises a ground fault detector, one of said conductors is adapted to be grounded at said AC power source, and said ground fault detector is operative to provide an error signal voltage at said bridge output terminals in response to an abnormal leakage current to ground from one of said conductors.
Claim 9
Dependent Claim
32 words
The ground fault detector of claim 7 wherein said core means comprises a pair of saturable reactor cores, and each of said conductors provides control windings on both of said reactor cores.
Claim 10
Dependent Claim
41 words
The ground fault detector of claim 8 further including current interrupting-means coupled to the output terminals of said bridge for disconnecting said load from said source of AC power in response to an error signal voltage at said bridge output terminals.
Claim 11
Dependent Claim
54 words
The ground fault detector of claim 9 wherein said current interrupting means comprises a voltage peak detector coupled to said bridge output terminals, a solenoid coupled to the output of said peak detector, and a circuit breaker switch connected in an ungrounded one of said conductors and adapted to be actuated by said solenoid.
Claim 12
Dependent Claim
32 words
The ground fault detector of claim 10 wherein said peak detector comprises a voltage doubler and filter, and said interrupting means further includes an amplifier coupled between said doubler-filter and said solenoid.
Claim 13
Dependent Claim
180 words
The ground fault detector of claim 11 wherein said reactor cores, said bridge windings and said control windings comprise a magnetic amplifier, the windings forming said inductance bridge comprise, first, second, third and fourth gate windings each having approximately the same number of turns, said first and fourth gate windings are wound on one of said reactor cores, said second and third gate windings are wound on the other of said reactor cores, said first and second gate windings are serially connected in the same sense across said bridge input terminals, said third and fourth gate windings are serially connected in the same sense across said bridge input terminals, said bridge output terminals comprise the junction of said first and second gate windings and the junction of said third and fourth gate windings, and in the presence of a current imbalance between said conductors the output of said oscillator functions as a carrier and The unbalanced currents through said control windings function as a modulating signal to provide a modulated voltage error signal at the output terminals of said bridge.
Claim 14
Dependent Claim
36 words
The ground fault detector of claim 7 wherein said AC power source has a frequency of approximately 60 hertz and said oscillator has an operating frequency selected from a range of 400 hertz to 2500 hertz.
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) | 1975-06-20 | 1975-12-20 | 1976-06-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-20 | 1979-12-20 | 1980-06-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-20 | 1983-12-20 | 1984-06-20 | $7700.00 | Window Closed / Lapsed |