US3736468A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ground fault interrupter apparatus
Assignee: Westinghouse Electric Corp
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Filing: 1971-06-30
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Granted: 1973-05-29
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Expires: 1991-06-30
Abstract
Abstract A differential transformer for sensing the fault current in a ground fault interrupter includes a magnet toroid with the power leads extending through it in a co-axial arrangement to provide single turn primary conductors. Stray current resulting from uneven placement of the power conductors within the toroid is thereby avoided; the relation of each of the coaxial conductors to the toroid is the same. Single turn coaxial conductors are highly advantageous in providing a miniaturized differential transformer with which there may be employed new miniature trip circuits of solid state components providing good noise immunity, high input impedance, inverse time delay and temperature compensation.
Inventors
- 👤 J Reeves
- 👤 G Bogel
- 👤 F Thompson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 01:25
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/33; G; G06; G06F; G06F11/00; G06F11/07; G06F11/08; G06F11/10; G06F9/00; G06F9/06; G06F9/30; G06F9/32; G06F9/321; H03; H03K; H03K21/00
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
136 words
A ground fault interrupter of the differential transformer type comprising: a toroidal magnet core having a center aperture; at least two primary conductors and means connecting said primary conductors between an alternating current source and a load, said at least two primary conductors extending through said aperture in said core and comprising only a single turn on said core, said at least two primary conductors being coaxial at least over the length thereof in said aperture; a secondary winding around said core; trip circuit means connected with said secondary winding for developing an electrical actuating signal only upon occurrence of a ground fault of a predetermined magnitude; and circuit brEaker means connected to be responsive to said actuating signal from said trip circuit to open the current path through at least one of said primary conductors.
Claim 2
Dependent Claim
136 words
A ground fault interrupter of the differential transformer type comprising: a toroidal magnet core having a center aperture; at least two primary conductors and means connecting said primary conductors between an alternating current source and a load, said at least two primary conductors extending through said aperture in said core and comprising only a single turn on said core, said at least two primary conductors being coaxial at least over the length thereof in said aperture; a secondary winding around said core; trip circuit means connected with said secondary winding for developing an electrical actuating signal only upon occurrence of a ground fault of a predetermined magnitude; and circuit brEaker means connected to be responsive to said actuating signal from said trip circuit to open the current path through at least one of said primary conductors.
Claim 3
Dependent Claim
103 words
The subject matter of claim 1 wherein: said trip circuit comprises a solid state switching device having a pair of terminals connected to cause actuation of said circuit breaker means when a highly conductive current path exists between said main terminals, said solid state switching device also having a control terminal, at least a first solid state amplifying device resistively biased to a point just into its cut-off characteristic and having supplied thereto a signal from said secondary winding to supply a firing signal to the control terminal of said switching device only upon occurrence of a predetermined signal from said secondary winding.
Claim 4
Dependent Claim
89 words
The subject matter of claim 2 wherein: said trip circuit comprises a rectifier means to rectify AC line voltage; said first solid state amplifying device has resistive bias means including a temperature compensated resistive element; a second solid state amplifying device is connected to receive the output of said first solid state amplifying device only upon a predetermined time delay inversely related to the magnitude of said output, the output of said second solid state amplifying device being connected to said control terminal of said solid state switching device.
Claim 5
Dependent Claim
26 words
The subject matter of claim 3 wherein: said solid state switching device is a thyristor and said first and second solid state amplifying devices are transistors.
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) | 1976-05-28 | 1976-11-27 | 1977-05-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-05-28 | 1980-11-27 | 1981-05-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-05-28 | 1984-11-27 | 1985-05-29 | $7700.00 | Window Closed / Lapsed |