US3611038A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ground fault and high current responsive circuit breaker utilizing amplified signals
Assignee: Hydrotech Chemical Corp
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Filing: 1969-09-08
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Granted: 1971-10-05
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Expires: 1989-09-08
Abstract
Abstract This invention relates to protective circuit means wherein a differential transformer and a current transformer are interposed between the AC line and a load device connected thereto, the transformers being adapted to respond, respectively, to leakage conditions and to overload conditions in the load devices. The protective circuit includes separate sensing amplifiers respectively responsive to the leakage or overload conditions, whichever occurs at any time, to produce a fault signal, and a trip signal generator responsive to the fault signal and to open circuit breaker contacts in the AC line and so remove power from the load device in the presence of the undesirable leakage and overload conditions until they have passed. A feature of the novel circuit is a simple test circuit simulating the fault conditions.
Inventors
- 👤 Ralph E Benham
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 23:04
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/08; H02H3/10; H02H3/105; H02H3/26; H02H3/32; H02H3/33
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
422 words
A protective circuit for AC powerlines and load equipment connected thereto, said circuit comprising: a differential transformer having the lines of the AC powerline connected therethrough equally and in opposing phase polarity to form primary and secondary windings normally having current cancellation properties, and having a third winding therein to sense the presence of any inequality in the currents in said primary and secondary windings and adapted to develop an output voltage in the presence of such inequality; a first-pulse circuit connected to said third winding and having an output at which pulses are present which correspond to the output from said third winding; a first circuit sense amplifier connected to said first pulse circuit, said first sense amplifier having an output circuit in which said pulses appear; a first rectifier circuit coupled via a capacitor to the output of said first sense amplifier; a current transformer having a primary winding connected in series with one of said AC powerlines and a secondary winding adapted to produce an output current related to the current in said current transformer primary winding; a second pulse circuit connected to said secondary winding of said current transformer and having an output at which pulses are present which correspond to the output from said current transformer secondary winding; a second circuit sense amplifier connected to said second pulse circuit, said second sense amplifier having an output circuit in which said second pulses appear; a second rectifier circuit coupled via a capacitor to the output of said second sense amplifier; an FET amplifier connected to both said first and said second rectifier circuit, said FET amplifier having an output circuit and being responsive to whichever of said rectifier circuits is producing a signal, derived from respective first and second pulses applied thereto, to produce a control signal; a unijunction transistor, having an input circuit coupled to the output of said FET amplifier and being responsive to the control signal therein to produce a trigger signal when said control signal is present; and a normally conductive SCR relay circuit having a gate circuit coupled to saiD unijunction transistor and being responsive to said trigger signal to become conductive, said relay circuit having a relay therein and normally closed contacts on said relay connected in series between said AC powerline and said load equipment, whereby whenever either an unbalanced condition in said differential transformer or an excess current condition occurs in said current transformer said SCR relay circuit will be actuated to disconnect an AC powerline from said load equipment.
Claim 2
Dependent Claim
422 words
A protective circuit for AC powerlines and load equipment connected thereto, said circuit comprising: a differential transformer having the lines of the AC powerline connected therethrough equally and in opposing phase polarity to form primary and secondary windings normally having current cancellation properties, and having a third winding therein to sense the presence of any inequality in the currents in said primary and secondary windings and adapted to develop an output voltage in the presence of such inequality; a first-pulse circuit connected to said third winding and having an output at which pulses are present which correspond to the output from said third winding; a first circuit sense amplifier connected to said first pulse circuit, said first sense amplifier having an output circuit in which said pulses appear; a first rectifier circuit coupled via a capacitor to the output of said first sense amplifier; a current transformer having a primary winding connected in series with one of said AC powerlines and a secondary winding adapted to produce an output current related to the current in said current transformer primary winding; a second pulse circuit connected to said secondary winding of said current transformer and having an output at which pulses are present which correspond to the output from said current transformer secondary winding; a second circuit sense amplifier connected to said second pulse circuit, said second sense amplifier having an output circuit in which said second pulses appear; a second rectifier circuit coupled via a capacitor to the output of said second sense amplifier; an FET amplifier connected to both said first and said second rectifier circuit, said FET amplifier having an output circuit and being responsive to whichever of said rectifier circuits is producing a signal, derived from respective first and second pulses applied thereto, to produce a control signal; a unijunction transistor, having an input circuit coupled to the output of said FET amplifier and being responsive to the control signal therein to produce a trigger signal when said control signal is present; and a normally conductive SCR relay circuit having a gate circuit coupled to saiD unijunction transistor and being responsive to said trigger signal to become conductive, said relay circuit having a relay therein and normally closed contacts on said relay connected in series between said AC powerline and said load equipment, whereby whenever either an unbalanced condition in said differential transformer or an excess current condition occurs in said current transformer said SCR relay circuit will be actuated to disconnect an AC powerline from said load equipment.
Claim 3
Dependent Claim
57 words
In the protective circuit defined in claim 1, a test circuit connected between said current transformer primary and a point of reference potential and including a pair of normally open switches for manually connecting said test circuit to said protective circuit to simulate either a leakage or overload condition to check the operation of the protective circuit.
Claim 4
Dependent Claim
73 words
In the protective circuit defined in claim 1, a regulated power supply having positive and negative voltage outputs connected to said first and second integrated circuit sense amplifiers and having an output potentiometer control across the output of said power supply, said potentiometer having an arm connected in common to said first and second rectifier circuits to provide an adjustable bias level to said rectifier circuits for setting the conductive operational level thereof.
Claim 5
Dependent Claim
232 words
A protective circuit for AC powerlines and load equipment connected thereto, said circuit comprising: a differential transformer, the AC powerlines being wound thereon in phase opposition as balanced primary and secondary windings, and having a tertiary winding adapted to develop a voltage signal indicative of the condition of unbalance in the AC current through said primary and secondary windings; a current transformer having a primary winding in series with one of said AC powerlines following said differential transformer and a secondary winding adapted to develop a current indicative of the current in said primary of said current transformer; a first-sensing circuit connected to said tertiary winding; a second-sensing circuit connected to said secondary winding of said current transformer, said first- and second-sensing circuits each including amplifier means; a normally inoperative control signal generator; an enabling amplifier connected to said control signal generator and to both said sensing circuits and adapted to be responsive to whichever of said sensing circuits is receiving current from said differential transformer or said current transformer to develop an enabling signal applied to said control signal generator so that said generator is rendered operative; and a circuit-interrupting means connected in said AC powerline and coupled to said sensing circuits, said interrupting being responsive to said control signal to interrupt the AC line connection to the load equipment in the presence of said leakage or said excess current conditions.
Claim 6
Dependent Claim
232 words
A protective circuit for AC powerlines and load equipment connected thereto, said circuit comprising: a differential transformer, the AC powerlines being wound thereon in phase opposition as balanced primary and secondary windings, and having a tertiary winding adapted to develop a voltage signal indicative of the condition of unbalance in the AC current through said primary and secondary windings; a current transformer having a primary winding in series with one of said AC powerlines following said differential transformer and a secondary winding adapted to develop a current indicative of the current in said primary of said current transformer; a first-sensing circuit connected to said tertiary winding; a second-sensing circuit connected to said secondary winding of said current transformer, said first- and second-sensing circuits each including amplifier means; a normally inoperative control signal generator; an enabling amplifier connected to said control signal generator and to both said sensing circuits and adapted to be responsive to whichever of said sensing circuits is receiving current from said differential transformer or said current transformer to develop an enabling signal applied to said control signal generator so that said generator is rendered operative; and a circuit-interrupting means connected in said AC powerline and coupled to said sensing circuits, said interrupting being responsive to said control signal to interrupt the AC line connection to the load equipment in the presence of said leakage or said excess current conditions.
Claim 7
Dependent Claim
101 words
In the protective circuit defined in claim 4, a test circuit connected across the AC line at the output connection of the primary of said current transformer to the load equipment connected thereto, and from said output connection to said secondary winding of said current transformer at the connection thereof to said second-sensing circuit, said test circuit including respective normally open switches between said output connection and the respective current transformer connections thereof, said switches being respectively manually operative to apply a simulated overload or unbalance signal condition to energize said relay thereby to test the operation of said protective circuit.
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) | 1974-10-04 | 1975-04-05 | 1975-10-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-10-04 | 1979-04-05 | 1979-10-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-10-04 | 1983-04-05 | 1983-10-05 | $7700.00 | Window Closed / Lapsed |