US3852642A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Sensing amplifier and trip circuit particularly for ground fault circuit interrupter
Assignee: Westinghouse Electric Corp
•
Filing: 1972-11-01
•
Granted: 1974-12-03
•
Expires: 1992-11-01
Abstract
Abstract Ground fault interrupter apparatus of the differential transformer type is provided with a sensing amplifier and trip circuit that includes an operational amplifier operated in a manner so that the interrupter apparatus is less sensitive to capacitive ground faults than it is to resistive ground faults. The quality of less sensitivity to capacitive ground faults is preferably obtained by applying to the operational amplifier a biasing voltage that is a half-wave rectified, unfiltered, voltage which aids in maintaining the inputs to the operational amplifier as a pure current source while using only a small number of components that is advantageous for reduced size.
Inventors
- 👤 J Engel
- 👤 R Elms
- 👤 J Misencik
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 15:12
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/33; H02H3/337
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
56 words
Electronic apparatus comprising: a source of sensed signals; amplifier means receiving sensed signals directly from said source; means to supply to said amplifier means an operating supply that is a half-wave rectified voltage; and a sold state switching device responsive to a predetermined output of said amplifier means to result in a change of conductive state.
Claim 2
Dependent Claim
56 words
Electronic apparatus comprising: a source of sensed signals; amplifier means receiving sensed signals directly from said source; means to supply to said amplifier means an operating supply that is a half-wave rectified voltage; and a sold state switching device responsive to a predetermined output of said amplifier means to result in a change of conductive state.
Claim 3
Dependent Claim
135 words
The subject matter of claim 1 wherein: said source of sensed signals in a sensing coil of a differential current transformer; said amplifier means is an operational amplifier having a pair of input terminals to which said sensed signals are applied, a pair of bias terminals to one of which said half-wave rectified voltage is supplied while the other of said bias terminals is at a relatively fixed potential, and an output terminal; and said solid state switching device is a thyristor having a pair of main terminals connected in series with a circuit element to be actuated when a highly conductive current path exists between said main terminals said thyristor also having a control terminal operatively connected to said output terminal of said operational amplifier to be responsive to predetermined magnitude output signals thereof.
Claim 4
Dependent Claim
41 words
The subject matter of claim 2 wherein: said means to supply an operating supply to said amplifier comprises an A.C. source and a diode rectifier; said thyristor is connected by said main terminals in series aiding direction with said diode rectifier.
Claim 5
Dependent Claim
136 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 A.C. electrical distribution system, and a secondary sensing winding on said core for sensing current unbalance between said primary windings; means responsive to a predetermined sensed signal on said sensing winding to result in opening of said line conductor, said means comprising amplifier means having inputs connected directly to the two ends of said sensing winding, bias means for said amplifier means comprising means to supply between two bias terminals of said amplifier means a potential difference that is periodically zero, and a solid state switching device responsive to a predetermined output of said amplifier means to energize a trip coil of a circuit breaker.
Claim 6
Dependent Claim
136 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 A.C. electrical distribution system, and a secondary sensing winding on said core for sensing current unbalance between said primary windings; means responsive to a predetermined sensed signal on said sensing winding to result in opening of said line conductor, said means comprising amplifier means having inputs connected directly to the two ends of said sensing winding, bias means for said amplifier means comprising means to supply between two bias terminals of said amplifier means a potential difference that is periodically zero, and a solid state switching device responsive to a predetermined output of said amplifier means to energize a trip coil of a circuit breaker.
Claim 7
Dependent Claim
23 words
The subject matter of claim 4 wherein: said amplifier means is an operational amplifier and said solid state switching device is a thyristor.
Claim 8
Dependent Claim
79 words
An operating circuit of an operational amplifier comprising: a sensing coil of a differential transformer connected across first and second input terminals of the operational amPlifier; means to supply a bias potential to first and second bias terminals of the operational amplifier, said bias potential between said bias terminals being periodically zero for an interval; and an averaging network, comprising an energy storage means, connected between an output terminal of the operational amplifier and one of said input terminals.
Claim 9
Dependent Claim
79 words
An operating circuit of an operational amplifier comprising: a sensing coil of a differential transformer connected across first and second input terminals of the operational amPlifier; means to supply a bias potential to first and second bias terminals of the operational amplifier, said bias potential between said bias terminals being periodically zero for an interval; and an averaging network, comprising an energy storage means, connected between an output terminal of the operational amplifier and one of said input terminals.
Claim 10
Dependent Claim
87 words
The subject matter of claim 6 wherein: said sensing coil is directly connected to said input terminals; said means to supply a bias potential comprises an alternating current supply comprising line and neutral conductors, said first bias terminal is connected to said line conductor with a half-wave rectifier therebetween and said second bias terminal is connected to said neutral conductor; and said energy storage means of said averaging network is a capacitor that is reset to zero charge during the interval in which said potential is zero.
Claim 11
Dependent Claim
47 words
The subject matter of claim 7 wherein: one side of said capacitor is directly connected to said output terminal and the other side of said capacitor is directly connected to said input terminal; said averaging network also comprising a first resistive impedance in parallel with said capacitor.
Claim 12
Dependent Claim
67 words
The subject matter of claim 8 wherein: a single series connection between said line and neutral conductors comprises a solenoid coil, said half wave rectifier and a solid state switching device; said solid state switching device having a control terminal connected to the output terminal of said operational amplifier through at least a second resistive impedance which is connected between said capacitor and said first resistive impedance.
Claim 13
Dependent Claim
105 words
An operating circuit of an operational amplifier in a sense amplifier and trip circuit of a ground fault interrupter for an alternating current systems comprising: means to supply sensed signals to be amplified to first and second input terminals of said operational amplifier; means to supply a bias potential to first and second bias terminals of the operational amplifier; and an averaging network, comprising an energy storage means, connected between an output terminal of the operational amplifier and one of said input terminals; and means to reset said energy storage means to zero periodically in synchronism with the line voltage of the alternating current system.
Claim 14
Dependent Claim
105 words
An operating circuit of an operational amplifier in a sense amplifier and trip circuit of a ground fault interrupter for an alternating current systems comprising: means to supply sensed signals to be amplified to first and second input terminals of said operational amplifier; means to supply a bias potential to first and second bias terminals of the operational amplifier; and an averaging network, comprising an energy storage means, connected between an output terminal of the operational amplifier and one of said input terminals; and means to reset said energy storage means to zero periodically in synchronism with the line voltage of the alternating current system.
Claim 15
Dependent Claim
47 words
The subject matter of claim 10 wherein: said means to reset said energy storage means is provided by said means for supplying potential to said bias terminals being a bias potential that is periodically zero for an interval sufficient to permit said energy storage means to reset.
Claim 16
Dependent Claim
93 words
Ground fault interrupter apparatus, exhibiting reduced sensitivity to capacitive ground faults as compared with resistive ground faults and suitable for economical and compact fabrication, comprising: a differential current transformer having a magnetic core for association with primary windings that are conductors of an electrical system to be protected by the apparatus and also having a sensing element for sensing current unbalance between the primary windings; an amplifier having at least one input terminal connected with said sensing element; bias supply means for supplying to said amplifier a bias potential that is periodically zero.
Claim 17
Dependent Claim
93 words
Ground fault interrupter apparatus, exhibiting reduced sensitivity to capacitive ground faults as compared with resistive ground faults and suitable for economical and compact fabrication, comprising: a differential current transformer having a magnetic core for association with primary windings that are conductors of an electrical system to be protected by the apparatus and also having a sensing element for sensing current unbalance between the primary windings; an amplifier having at least one input terminal connected with said sensing element; bias supply means for supplying to said amplifier a bias potential that is periodically zero.
Claim 18
Dependent Claim
40 words
Ground fault interrupter apparatus in accordance with claim 12 wherein: said bias supply means comprises a rectifier for half-wave rectifying AC line voltage and the half-wave rectified potential produced by said rectifier is supplied to said amplifier free of filtering.
Claim 19
Dependent Claim
38 words
Ground fault interrupter apparatus in accordance with claim 12 wherein: said sensing element has a pair of output terminals; and said amplifier has a pair of input terminals connected respectively to said output terminals of said sensing element.
Claim 20
Dependent Claim
21 words
Ground fault interrupter apparatus in accordance with claim 14 wherein: said sensing element is a sensing coil wound on said core.
Claim 21
Dependent Claim
33 words
Ground fault interrupter apparatus in accordaNce with claim 14 wherein: said input terminals of said amplifier and said output terminals of said sensing element are directly conductively connected without any appreciable impedance therebetween.
Claim 22
Dependent Claim
68 words
Ground fault interrupter apparatus in accordance with claim 14 wherein: said amplifier input terminals include an inverting input terminal and a non-inverting input terminal; said amplifier further having a pair of bias terminals, one of said bias terminals being maintained at a reference potential level, the other of said bias terminals being supplied from said bias supply means with potential that is periodically at said reference potential level.
Claim 23
Dependent Claim
55 words
Ground fault interrupter apparatus in accordance with claim 17, wherein: said amplifier has an output terminal; a feedback network is connected between said output terminal of said amplifier and one of said input terminals of said amplifier, said feedback network comprising a capacitor that is reset to zero charge when said bias potential is zero.
Claim 24
Dependent Claim
35 words
Ground fault interrupter apparatus in accordance with claim 13 wherein: said amplifier has an output terminal; and a solid state switch is provided having a control terminal connected with said output terminal of said amplifier.
Claim 25
Dependent Claim
56 words
Ground fault interrupter apparatus in accordance with claim 19 wherein: said solid state switch is in a circuit branch connected between conductors of an electrical system to be protected by the apparatus in series with said rectifier and with a solenoid trip coil of a circuit breaker to be tripped upon occurrence of a ground fault.
Claim 26
Dependent Claim
31 words
Ground fault interrupter apparatus in accordance with claim 20 wherein: said solid state switch has a rectifying characteristic and is in said circuit branch in series aiding direction with said rectifier.
Claim 27
Dependent Claim
56 words
Electronic apparatus comprising: an amplifier having a pair of input terminals, an output terminal, and a pair of bias terminals; a source of sensed signals connected across said pair of input terminals; a source of bias potential connected to one of said bias terminals, said source of bias potential supplying a potential that is periodically zero.
Claim 28
Dependent Claim
56 words
Electronic apparatus comprising: an amplifier having a pair of input terminals, an output terminal, and a pair of bias terminals; a source of sensed signals connected across said pair of input terminals; a source of bias potential connected to one of said bias terminals, said source of bias potential supplying a potential that is periodically zero.
Claim 29
Dependent Claim
20 words
The subject matter of claim 22 wherein: the other of said bias terminals is maintained at a reference zero potential.
Claim 30
Dependent Claim
24 words
The subject matter of claim 22 wherein: said source of sensed signals is connected directly to said input terminals with no appreciable impedance therebetween.
References Cited (Backward Citations)
US3213321A
Cited
US3407337A
Cited
US3550030A
Cited
US3621334A
Cited
US3683208A
Cited
US3673502A
Cited
US3700966A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-02 | 1978-06-03 | 1978-12-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-02 | 1982-06-03 | 1982-12-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-02 | 1986-06-03 | 1986-12-03 | $7700.00 | Window Closed / Lapsed |