US3710190A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fault current protective circuit for a load supplied from single or polyphase systems
Assignee: BBC Brown Boveri AG Switzerland
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Filing: 1972-02-07
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Granted: 1973-01-09
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Expires: 1992-02-07
Abstract
Abstract The protective circuit has a summation current transformer whose secondary winding has an auxiliary AC voltage applied thereto and is connected in series with a release, such as the operating coil of a circuit breaker. The auxiliary AC voltage has the same frequency as a main''s phase and is generated by a voltage source having a low internal resistance. The secondary winding of the transformer is dimensioned so that its impedance, with the transformer core magnetically unsaturated, is at least of the same order as the impedance of the release, and the internal resistance of the auxiliary voltage source, with the transformer core magnetically saturated, is low relative to these impedances. The auxiliary voltage source may be part of a voltage divider connected between one phase and either a neutral conductor or another main, and the voltage divider may comprise a condenser and a resistance. The release may be designed as a relay which is pre-polarized by an electromagnet excited by rectification from the same phase as the auxiliary AC voltage. Various additional circuit modifications may be made.
Inventors
- 👤 F Dankward
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 18:55
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/33; H02H3/332
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
126 words
In a fault current protective circuit for loads supplied from single or polyphase systems, and including a summation current transformer with a transformer core and whose secondary winding has an auxiliary AC voltage applied thereto and is connected in series with a release, the improvement comprising, in combination, said auxiliary AC voltage having the same frequency as a mains phase, and being generated by a voltage source having a low internal resistance; the secondary winding of said summation current transformer being dimensioned so that its impedance, with said transformer core magnetically unsaturated, is at least of the same order as the impedance of said release; the internal resistance of said auxiliary voltage source, with said transformer core magnetically saturated, being low relative to said aforementioned impedances.
Claim 2
Dependent Claim
126 words
In a fault current protective circuit for loads supplied from single or polyphase systems, and including a summation current transformer with a transformer core and whose secondary winding has an auxiliary AC voltage applied thereto and is connected in series with a release, the improvement comprising, in combination, said auxiliary AC voltage having the same frequency as a mains phase, and being generated by a voltage source having a low internal resistance; the secondary winding of said summation current transformer being dimensioned so that its impedance, with said transformer core magnetically unsaturated, is at least of the same order as the impedance of said release; the internal resistance of said auxiliary voltage source, with said transformer core magnetically saturated, being low relative to said aforementioned impedances.
Claim 3
Dependent Claim
32 words
In a fault current protective circuit, the improvement claimed in claim 1, in which said auxiliary voltage source comprises part of a voltage divider connected between one phase and the neutral conductor.
Claim 4
Dependent Claim
23 words
In a fault current protective circuit, the improvement claimed in claim 2, in which said voltage divider comprises a condenser and a resistance.
Claim 5
Dependent Claim
25 words
In a fault current protective circuit, the improvement claimed in claim 2, in which said release is a relay; and an electromagnet pre-polarizing said relay.
Claim 6
Dependent Claim
33 words
In a fault current protective circuit, the improvement claimed in claim 4, in which said electromagnet is excited by rectification from the same phase as that to which said voltage divider is connected.
Claim 7
Dependent Claim
72 words
In a fault current protective circuit, the improvement claimed in claim 1, including an impedance network connected to said mains and to a neutral or to another main and creating an artificial neutral point; and an additional auxiliary control winding on said transformer core connected to taps of said impedance network in a manner such that, in case of a phase failure, a current activating the fault current protective circuit will flow.
Claim 8
Dependent Claim
41 words
In a fault current protective circuit, the improvement claimed in claim 1, in which the load has a separate protective conductor; said separate protective conductor being connected to an auxiliary ground through an additional auxiliary control winding on said transformer core.
Claim 9
Dependent Claim
32 words
In a fault current protective circuit, the improvement claimed in claim 1, including additional auxiliary control windings on said transformer core operable to activate said protective circuit by other fault indicating currents.
Claim 10
Dependent Claim
24 words
In a fault current protective circuit, the improvement claimed in claim 8, in which said auxiliary control windings are responsive to currents from thermocouples.
Claim 11
Dependent Claim
46 words
In a fault current protective circuit, the improvement claimed in claim 6, including a pair of diodes connected in parallel with each other, with opposed polarity, in series between a tap and said auxiliary control winding and serving as a threshold value switch preventing false releases.
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) | 1976-01-09 | 1976-07-10 | 1977-01-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-09 | 1980-07-10 | 1981-01-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-09 | 1984-07-10 | 1985-01-09 | $7700.00 | Window Closed / Lapsed |