US4063301A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Half-wave detector for alternating current static switches
Assignee: CGEE ALSTHOM NORTH AMERICA Inc
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Filing: 1976-08-09
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Granted: 1977-12-13
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Expires: 1996-08-09
Abstract
Abstract A circuit for monitoring conduction of a phase controlled, alternating current switch, e.g., a thyristor switch, looks at the voltage across the switch. This voltage has a high dv/dt whenever the switch stops and starts conducting current. The voltage detected from across the switch is processed as follows: it is differentiated to produce a train of voltage spikes of very short time duration and some lesser voltages; the lesser voltages are removed; the spikes are then amplified and extended in time duration; and finally the time extended spikes are integrated. The integrated voltage is a train of alternate positive and negative voltages averaging zero during normal switch operation. However, when the switch conducts one of the half cycles only, the integrated voltage rises in one polarity sense depending upon the half cycle conducted. A control circuit becomes operative upon the integrated voltage attaining a predetermined value to initiate a control function such as de-energize the switch.
Inventors
- 👤 Ronald William Lye
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 02:54
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/10; H02H7/12
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
184 words
A circuit for monitoring conduction of a phase controlled, alternating current switching device comprising means for detecting the voltage across said switching device; a differentiator for differentiating said voltage to obtain a train of positive and negative voltage pulses of short time duration and other voltages of lesser peak values, each rapid change of said voltage in one direction producing a pulse of one polarity and each rapid change in the other direction producing a pulse of the other polarity; a threshold circuit for passing voltage pulses in excess of said lesser peak values; an amplifier for amplifying the voltage pulses passed by said threshold circuit; an extender circuit for lengthening the time duration of said amplified pulses; an integrator for integrating said time lengthened pulses and putting out alternate positive and negative voltages averaging zero in value during normal operation of said switching device and during abnormal operation when the switching device conducts half-waves of one polarity only putting out an incrasing voltage of one polarity only; and means responsive to a predetermined value of said increasing voltage for initiating a control function.
Claim 2
Dependent Claim
184 words
A circuit for monitoring conduction of a phase controlled, alternating current switching device comprising means for detecting the voltage across said switching device; a differentiator for differentiating said voltage to obtain a train of positive and negative voltage pulses of short time duration and other voltages of lesser peak values, each rapid change of said voltage in one direction producing a pulse of one polarity and each rapid change in the other direction producing a pulse of the other polarity; a threshold circuit for passing voltage pulses in excess of said lesser peak values; an amplifier for amplifying the voltage pulses passed by said threshold circuit; an extender circuit for lengthening the time duration of said amplified pulses; an integrator for integrating said time lengthened pulses and putting out alternate positive and negative voltages averaging zero in value during normal operation of said switching device and during abnormal operation when the switching device conducts half-waves of one polarity only putting out an incrasing voltage of one polarity only; and means responsive to a predetermined value of said increasing voltage for initiating a control function.
Claim 3
Dependent Claim
54 words
A circuit according to claim 1 wherein said control function initiating means comprises a pair of rectifiers connected in parallel in the same polarity sense between the output of said integrator and a relay driver; an inverter connected between one of said rectifiers and said integrator output; and a relay operated by said driver.
Claim 4
Dependent Claim
21 words
A circuit according to claim 2 wherein said relay is operative to de-energize said switching device upon said abnormal operation thereof.
Claim 5
Dependent Claim
31 words
A circuit according to claim 2 wherein said relay driver comprises means for blocking voltage below a predetermined value and an amplifier for amplifying the voltages let through the blocking means.
Claim 6
Dependent Claim
47 words
A circuit according to claim 1 wherein said voltage detecting means comprises a potential transformer having its primary winding connected across said switching device; and a buffer having its input connected to the secondary winding of said transformer and its output to the input of said differentiator.
Claim 7
Dependent Claim
18 words
A circuit according to claim 5 wherein said buffer includes means for reducing the voltage to said differentiator.
Claim 8
Dependent Claim
14 words
A circuit according to claim 1 wherein said extender circuit is a capacitor circuit.
Claim 9
Dependent Claim
132 words
A circuit for monitoring conduction of a phase controlled, alternating current switching device comprising a potential transformer having its primary winding connected across said switching device; a voltage reducing buffer having its input connected to the secondary winding of said potential transformer; a differentiator having its input connected to the output of said buffer; a threshold circuit having its input connected to the output of said differentiator; an amplifier having its input connected to the output of said threshold circuit; a signal extender having its input connected to the output of said amplifier; an integrator having its input connected to the output of said signal extender; a rectifier having its input connected to the output of said integrator; and a relay driver having its input connected to the output of said rectifier.
Claim 10
Dependent Claim
132 words
A circuit for monitoring conduction of a phase controlled, alternating current switching device comprising a potential transformer having its primary winding connected across said switching device; a voltage reducing buffer having its input connected to the secondary winding of said potential transformer; a differentiator having its input connected to the output of said buffer; a threshold circuit having its input connected to the output of said differentiator; an amplifier having its input connected to the output of said threshold circuit; a signal extender having its input connected to the output of said amplifier; an integrator having its input connected to the output of said signal extender; a rectifier having its input connected to the output of said integrator; and a relay driver having its input connected to the output of said rectifier.
Claim 11
Dependent Claim
31 words
A circuit according to claim 8 wherein said switching device comprises a plurality of thyristors that are phase controlled to control current flow in a reactor in a static var controller.
Claim 12
Dependent Claim
31 words
A circuit according to claim 3 wherein said relay driver comprises means for blocking voltage below a predetermined value and an amplifier for ampliflying the voltages let through the blocking means.
References Cited (Backward Citations)
US3646398A
Cited
US4001671A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-12-12 | 1981-06-13 | 1981-12-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-12-12 | 1985-06-13 | 1985-12-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-12-12 | 1989-06-13 | 1989-12-13 | $7700.00 | Window Closed / Lapsed |