US3815013A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Current transformer with active load termination
Assignee: General Electric Co
•
Filing: 1973-05-31
•
Granted: 1974-06-04
•
Expires: 1993-05-31
Abstract
Abstract A current transformer and transresistance amplifier are combined; the secondary winding of the current transformer being connected to the input of the transresistance amplifier and being virtually short-circuited because of the very low input impedance of the transresistance amplifier. The transresistance amplifier, nevertheless, supplies an output voltage which is proportional to current in the primary winding of the current transformer. An output voltage is developed from the current in the secondary winding. An important advantage, among others, of the subject combination is that a current transformer having considerably lower volt-ampere capacity may be employed. A current transformer employed alone for the same purpose would have to have a much larger volt-ampere capacity.
Inventors
- 👤 M Milkovic
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 16:11
CPC Classifications
G; G01; G01R; G01R15/00; G01R15/14; G01R15/18; G01R15/183; H; H01; H01F; H01F38/00; H01F38/20; H01F38/22; H01F38/28; H01F38/32; H02; H02H; H02H3/00; H02H3/02; H02H3/05
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
51 words
In combination: a current transformer including primary and secondary windings adapted for conducting primary and secondary currents, respectively; and, a transresistance amplifier for terminating said secondary winding and serving as an active load which virtually short-circuits said secondary wiNding while supplying an output voltage proportional to the primary current, if any.
Claim 2
Dependent Claim
51 words
In combination: a current transformer including primary and secondary windings adapted for conducting primary and secondary currents, respectively; and, a transresistance amplifier for terminating said secondary winding and serving as an active load which virtually short-circuits said secondary wiNding while supplying an output voltage proportional to the primary current, if any.
Claim 3
Dependent Claim
32 words
The combination according to claim 1 further comprising means coupled with said transresistance amplifier for supplying in response to said output voltage another output voltage phase-inverted with respect to said output voltage.
Claim 4
Dependent Claim
136 words
In combination: a current transformer comprising primary and secondary windings adapted for conducting primary and secondary currents, respectively; and an operational amplifier including first and second input terminal means, output terminal means, and a feedback resistance connected between said first input terminal means and said output terminal means, said operational amplifier having a high open-loop gain and a low input resistance, measurable between said first and second input terminal means, said secondary winding being connected between said first and second input terminal means and in parallel with said low input resistance whereby there is no substantial potential difference between said first and second input terminals even when said secondary winding conducts secondary current, said operational amplifier supplying, between said output terminal means and said second input terminal means, an output voltage proportional to said primary current.
Claim 5
Dependent Claim
136 words
In combination: a current transformer comprising primary and secondary windings adapted for conducting primary and secondary currents, respectively; and an operational amplifier including first and second input terminal means, output terminal means, and a feedback resistance connected between said first input terminal means and said output terminal means, said operational amplifier having a high open-loop gain and a low input resistance, measurable between said first and second input terminal means, said secondary winding being connected between said first and second input terminal means and in parallel with said low input resistance whereby there is no substantial potential difference between said first and second input terminals even when said secondary winding conducts secondary current, said operational amplifier supplying, between said output terminal means and said second input terminal means, an output voltage proportional to said primary current.
Claim 6
Dependent Claim
44 words
The combination according to claim 3 wherein said input resistance of said operational amplifier is defined as: Ri about Rf/Ao where Ri is the input resistance, Rf is the magnitude of said feedback resistance, and Ao is the open-loop gain of said operational amplifier.
Claim 7
Dependent Claim
14 words
The combination according to claim 4 wherein Ri is not greater than 0.5 ohm.
Claim 8
Dependent Claim
72 words
The combination according to claim 3 wherein said output voltage is defined as: Vo - Is Rf - Ip Rf/K where Vo is the magnitude of the output voltage, Is is the magnitude of the secondary current, Rf is the magnitude of the feedback resistance, Ip is the magnitude of the primary current, and K Ns/Np, and Ns and Np are the number of turns on the secondary and primary windings, respectively.
Claim 9
Dependent Claim
52 words
The combination according to claim 3 wherein said output voltage is a varying voltage which may include a DC component and said combination according to claim 3 is further comprised of means connected between said output terminal means and said second terminal means for translating said output voltage without said DC component.
Claim 10
Dependent Claim
32 words
The combination according to claim 3 further comprising inverting operational amplifier means, responsive to said output voltage, for supplying another output voltage which is phase-inverted 180* with respect to said output voltage.
Claim 11
Dependent Claim
46 words
In combination: a transformer including at least one secondary winding adapted for conducting secondary current; and, operational amplifier means serving as an active load for terminating said secondary winding in a virtual short circuit while supplying an output voltage proportional to said secondary current, if any.
Claim 12
Dependent Claim
46 words
In combination: a transformer including at least one secondary winding adapted for conducting secondary current; and, operational amplifier means serving as an active load for terminating said secondary winding in a virtual short circuit while supplying an output voltage proportional to said secondary current, if any.
Claim 13
Dependent Claim
56 words
The combination according to claim 9, wherein said operational amplifier means includes input and output terminal means and a feedback resistance connected between said input and output terminal means, said output voltage being defined as: Vo - Is Rf where Vo is the output voltage, Is is the secondary current, and Rf is the feedback resistance.
Claim 14
Dependent Claim
47 words
The combination according to claim 9 wherein said output voltage is a varying voltage which may include a DC component and said combination according to claim 9 is further comprised of means coupled with said operational amplifier means for translating said output voltage without its DC component.
Claim 15
Dependent Claim
61 words
In combination: a current transformer including primary and secondary windings; a high gain amplifier including first and second input terminals between which said secondary winding is connected so that said amplifier represents a very low impedance connected across said secondary winding, said amplifier including an output terminal; and, a feedback impedance connected between said first input terminal and said output terminal.
Claim 16
Dependent Claim
61 words
In combination: a current transformer including primary and secondary windings; a high gain amplifier including first and second input terminals between which said secondary winding is connected so that said amplifier represents a very low impedance connected across said secondary winding, said amplifier including an output terminal; and, a feedback impedance connected between said first input terminal and said output terminal.
Claim 17
Dependent Claim
100 words
The combination according to claim 12 wherein the primary and secondary windings are adapted for conducting primary and secondary currents, respectively, and the very low impedance of said amplifier virtually short-circuits said secondary windings so that no substantial difference of potential exists between said first and second input terminals while substantially all of the secondary current is conducted from said first input terminal through said feedback impedance to said output terminal so that between said output terminal and said second input terminal there exists a potential difference substantially equal to the product of the secondary current and the feedback impedance.
Claim 18
Dependent Claim
62 words
The combination according to claim 13 wherein said potential difference between said output terminal and said second input terminal is a varying potential difference which may include a DC component and said combination according to claim 13 is further comprised of means connected between said output terminal and said second input terminal for translating said varying potential difference without its DC component.
Claim 19
Dependent Claim
40 words
A current transformer including a current-carrying primary and a current-carrying secondary, and a transresistance amplifier terminating said secondary in a virtual short circuit while said amplifier, in response to the secondary current, supplies an output voltage proportional to primary current.
Claim 20
Dependent Claim
40 words
A current transformer including a current-carrying primary and a current-carrying secondary, and a transresistance amplifier terminating said secondary in a virtual short circuit while said amplifier, in response to the secondary current, supplies an output voltage proportional to primary current.
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) | 1977-06-03 | 1977-12-03 | 1978-06-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-03 | 1981-12-03 | 1982-06-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-03 | 1985-12-03 | 1986-06-04 | $7700.00 | Window Closed / Lapsed |