Patent US3699391A successfully refreshed from Google Patents.
US3699391A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Reactor fault relay
Assignee: United States Department of the Interior
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Filing: 1971-09-02
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Granted: 1972-10-17
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Expires: 1991-09-02
Abstract
Abstract A relay for protecting three-phase, wye-connected circuits by monitoring neutral voltage. To prevent relay operation during normal unbalanced conditions, the current input to each phase is monitored, and relay operation enabled only when three currents are present.
Inventors
- 👤 Larry E Eilts
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 17:57
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/34; H02H3/353; H02H3/16; H02H3/162; H02H3/165
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
96 words
An electrical circuit for preventing damage to a three phase wye-connected circuit having three input leads and a common neutral point, comprising: means for detecting the voltage at the neutral point and generating a first control signal in response to a change in neutral voltage, means for detecting current flow in the three input leads and producing a second control signal only when current is flowing in each of the three leads, means for disconnecting the three phase circuit from a power supply in response to the simultaneous occurrence of the first and second control signals.
Claim 2
Dependent Claim
96 words
An electrical circuit for preventing damage to a three phase wye-connected circuit having three input leads and a common neutral point, comprising: means for detecting the voltage at the neutral point and generating a first control signal in response to a change in neutral voltage, means for detecting current flow in the three input leads and producing a second control signal only when current is flowing in each of the three leads, means for disconnecting the three phase circuit from a power supply in response to the simultaneous occurrence of the first and second control signals.
Claim 3
Dependent Claim
77 words
An electrical circuit is claimed in claim 1 in which: the means for detecting the voltage at the neutral point and generating a first control signal includes a transformer for isolating neutral voltage signals, a variable gain amplifier in series with the transformer for varying the intensity of the neutral voltage signals, and a rectifier in series with the amplifier for converting neutral voltage signals to the first control signal for input to the means for disconnecting.
Claim 4
Dependent Claim
86 words
An electrical circuit as claimed in claim 1 in which: the means foR detecting current flow in the three input leads and producing a second control signal includes a transformer associated with each input lead for producing a representative voltage output in response to the presence of current flow in each lead, an amplifier for modifying the level of each representative voltage output, and a summer for producing the second control signal in response to the combined representative voltage outputs from all of the three leads.
Claim 5
Dependent Claim
58 words
An electrical circuit as claimed in claim 1 in which: the means for disconnecting the three phase circuit from a power supply includes a transistor switching circuit and a circuit breaker system, the switching circuit operating to suppress the effect of the first control signal upon the circuit breaker system unless the second control signal is simultaneously received.
Claim 6
Dependent Claim
202 words
An electrical circuit as claimed in claim 1 in which: the means for detecting the voltage at the neutral point and generating a first control signal includes a transformer for isolating neutral voltage signals, a variable gain amplifier in series with the transformer for varying the intensity of the neutral voltage signals, and a rectifier in series with the amplifier for converting neutral voltage signals to the first control signal for input to the means for disconnecting, the means for detecting current flow in the three input leads and producing a second control signal includes a transformer associated with each input lead for producing a representative voltage output in response to the presence of current flow in each lead, an amplifier for modifying the level of each representative voltage output and a summer for producing the second control signal in response to the combined representative voltage outputs from all of the three leads, and the means for disconnecting the three phase circuit from a power supply includes a transistor switching circuit and a circuit breaker system, the switching circuit operating to suppress the effect of the first control signal upon the circuit breaker system unless the second control signal is simultaneously received.
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) | 1975-10-17 | 1976-04-17 | 1976-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-17 | 1980-04-17 | 1980-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-17 | 1984-04-17 | 1984-10-17 | $7700.00 | Window Closed / Lapsed |