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US3662218A
Expired / Lapsed
US
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Ground fault interruptor circuit
Assignee: Individual
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Filing: 1970-06-19
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Granted: 1972-05-09
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Expires: 1990-06-19
Abstract
Abstract A circuit for actuating a circuit breaker to disconnect a load from across conductors connecting the load across an input circuit which has one neutral side upon the occurrence of an imbalance in the currents flowing in the conductors. The circuit includes a differential transformer having a bifilar pair of windings wound on a toroidal core, the winding being connected in series with separate conductors of the input circuit. The permeability of the toroidal core of the transformer is quite low when the currents in the two conductors are equal or almost equal and increases greatly to decrease the inductance of a sensing winding, also wound about the core and energized with a pulsating current, upon the occurrence of an imbalance in the currents flowing in the two conductors. The circuit includes a transistor and SCR circuit responsive to the change in the inductance of the sensing winding for energizing the circuit breaker upon an increase in the inductance of the sensing winding to disconnect the load from across the two conductors. The circuit may also include a check circuit for insuring that the windings of the differential transformer are properly connected across the input circuit.
Inventors
- 👤 George A Whitlow
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 19:09
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/33; H02H11/00; H02H11/002
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
236 words
A ground fault interruptor circuit for disconnecting a load from across an input circuit of alternating current, said interruptor circuit including: a pair of conductors for connecting a load across an input circuit of alternating current; a differential transformer having a core and a pair of windings, one of said windings being connected in one of said conductors and the other of said pair of windings being connected in the other of said conductors, alternating currents flowing through each of said windings tending to induce magnetic fluxes of opposite polarities in said core whereby the permeability of said core is small when equal currents flow in said windings, said transformer including a sensing winding whose inductance varies in accordance with the permeability of said core, aid core being toroidal in form and having square loop hysteresis characteristic; electrically operable switch means between said pair of windings and said load for disconnecting said load from said conductors; and control means responsive to the inductance of said sensing winding for actuating said switch means to disconnect said load from said conductors when the inductance of said sensing winding exceeds a predetermined value, said control means including means connectible across said input circuit and operatively associated with said sensing winding for energizing said sensing winding with a pulsating direct current of the same phase and the same frequency as the current flowing in one of said pair of windings.
Claim 2
Dependent Claim
236 words
A ground fault interruptor circuit for disconnecting a load from across an input circuit of alternating current, said interruptor circuit including: a pair of conductors for connecting a load across an input circuit of alternating current; a differential transformer having a core and a pair of windings, one of said windings being connected in one of said conductors and the other of said pair of windings being connected in the other of said conductors, alternating currents flowing through each of said windings tending to induce magnetic fluxes of opposite polarities in said core whereby the permeability of said core is small when equal currents flow in said windings, said transformer including a sensing winding whose inductance varies in accordance with the permeability of said core, aid core being toroidal in form and having square loop hysteresis characteristic; electrically operable switch means between said pair of windings and said load for disconnecting said load from said conductors; and control means responsive to the inductance of said sensing winding for actuating said switch means to disconnect said load from said conductors when the inductance of said sensing winding exceeds a predetermined value, said control means including means connectible across said input circuit and operatively associated with said sensing winding for energizing said sensing winding with a pulsating direct current of the same phase and the same frequency as the current flowing in one of said pair of windings.
Claim 3
Dependent Claim
42 words
The ground fault interruptor circuit of claim 1, wherein said control means comprises a control transistor operatively associated with said sensing winding and having an emitter-collector circuit which is rendered conductive when the inductance of said sensing winding exceeds said predetermined value.
Claim 4
Dependent Claim
59 words
The ground fault interruptor circuit of claim 2, wherein said switch means includes a fourth winding and contact means movable to open position when said fourth winding is energized, and rectifier means operatively associated with said control transistor and connected in series with said fourth winding, said rectifier means being rendered conductive when said emitter-collector circuit is rendered conductive.
Claim 5
Dependent Claim
50 words
The ground fault interruptor circuit of claim 3, and a polarity check circuit operatively associated with said control transistor for rendering said emitter-collector circuit conductive when the current flowing in said sensing winding is not of the same phase as the current flowing in said one one of said windings.
References Cited (Backward Citations)
US3213321A
Cited
US3407337A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-05-09 | 1975-11-08 | 1976-05-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-05-09 | 1979-11-08 | 1980-05-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-05-09 | 1983-11-08 | 1984-05-09 | $7700.00 | Window Closed / Lapsed |