US3818338A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetizing current compensating circuit
Assignee: Lorain Products Corp
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Filing: 1972-09-21
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Granted: 1974-06-18
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Expires: 1992-09-21
Abstract
Abstract A circuit for eliminating the effect of magnetizing current flow on load current measurements made through transformers. A current indicating network provides an output voltage proportional to both the magnetizing and load components of the current through a transformer without substantially affecting the magnitude of the voltage across or current through that transformer. A compensating current generating circuit generates a current which is equal in magnitude and opposite in phase to the magnetizing current flow through the transformer over a wide band of frequencies. This compensating current is applied to the current indicating network in cancelling relationship to the magnetizing current component of the current through the transformer to render the output voltage indication independent of magnetizing current flow so that the load current component can be accurately measured.
Inventors
- 👤 C Chambers
- 👤 F Kiko
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 17:51
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/02; G01R33/025; G01R19/00; G01R19/0092
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
113 words
In a circuit for improving the accuracy of current measurements made through transformers, in combination, a transformer having a primary winding, current indicating means for generating a voltage which varies in accordance with the current through the primary winding of said transformer, means for connecting said current indicating means to said transformer, compensating current generating means for generating a current having a magnitude substantially equal to the magnetizing current component of the current through said primary winding and having substantially a 180* phase displacement from said magnetizing current component, and means for connecting said compensating current generating means to said current indicating means to cancel the effect of said magnetizing current component thereupon.
Claim 2
Dependent Claim
113 words
In a circuit for improving the accuracy of current measurements made through transformers, in combination, a transformer having a primary winding, current indicating means for generating a voltage which varies in accordance with the current through the primary winding of said transformer, means for connecting said current indicating means to said transformer, compensating current generating means for generating a current having a magnitude substantially equal to the magnetizing current component of the current through said primary winding and having substantially a 180* phase displacement from said magnetizing current component, and means for connecting said compensating current generating means to said current indicating means to cancel the effect of said magnetizing current component thereupon.
Claim 3
Dependent Claim
22 words
A circuit as set forth in claim 1 including means for connecting said generating means across the primary winding of said transformer.
Claim 4
Dependent Claim
32 words
A circuit as set forth in claim 1 in which said generating means includes an operational amplifier having a feedback network adapted to cause said amplifier to exhibit an inductive voltage-current characteristic.
Claim 5
Dependent Claim
178 words
In a circuit for improving the accuracy of current measurements made through a load supplying transformer, in combination, a transformer having a primary winding and a secondary winding, means for connecting a load across said secondary winding, means for connecting an energizing source to said primary winding, current indicating means having input means and output means, said indicating means serving as means for generating a voltage at the output means thereof which is substantially proportional to the algebraic sum of the currents applied to the input means thereof, means for connecting said input means to said primary winding to conduct current through said primary winding, compensating current generating means having input means and output means, said generating means serving as means for generating from said output means a current which is substantially equal and opposite to the magnetizing component of current through said primary winding, means for connecting the input means of said generating means to said primary winding and means for connecting the output means of said generating means to the input means of said indicating means.
Claim 6
Dependent Claim
178 words
In a circuit for improving the accuracy of current measurements made through a load supplying transformer, in combination, a transformer having a primary winding and a secondary winding, means for connecting a load across said secondary winding, means for connecting an energizing source to said primary winding, current indicating means having input means and output means, said indicating means serving as means for generating a voltage at the output means thereof which is substantially proportional to the algebraic sum of the currents applied to the input means thereof, means for connecting said input means to said primary winding to conduct current through said primary winding, compensating current generating means having input means and output means, said generating means serving as means for generating from said output means a current which is substantially equal and opposite to the magnetizing component of current through said primary winding, means for connecting the input means of said generating means to said primary winding and means for connecting the output means of said generating means to the input means of said indicating means.
Claim 7
Dependent Claim
39 words
A circuit as set forth in claim 4 in which said indicating means includes an operational amplifier having an inverting input and an output, a resistor and means for connecting said resistor between said output and said inverting input.
Claim 8
Dependent Claim
54 words
A circuit as set forth in claim 4 in which said generating means includes an operational amplifier having an inverting input and an output, resistance-capacitance means for causing said operational amplifier to exhibit an inductive voltage-current characteristic and means for connecting said resistance-capacitance means to the output and inverting input of said operational amplifier.
Claim 9
Dependent Claim
138 words
In a circuit for improving the accuracy of current measurements made through a load supplying transformer, in combination, a transformer including a primary winding and a secondary winding, means for connecting a load across said secondary winding, current indicating means for producing an output which varies in accordance with the current throuGh said primary winding, means for connecting said primary winding and said current indicating means in series across a source of voltage, compensating current generating means for generating a current which is substantially equal to the magnetizing component of the current through said primary winding, means for connecting said compensating current generating means to said primary winding and means for applying the current produced by said generating means to said indicating means to cancel the effect of the magnetizing component of the current through said primary winding.
Claim 10
Dependent Claim
138 words
In a circuit for improving the accuracy of current measurements made through a load supplying transformer, in combination, a transformer including a primary winding and a secondary winding, means for connecting a load across said secondary winding, current indicating means for producing an output which varies in accordance with the current throuGh said primary winding, means for connecting said primary winding and said current indicating means in series across a source of voltage, compensating current generating means for generating a current which is substantially equal to the magnetizing component of the current through said primary winding, means for connecting said compensating current generating means to said primary winding and means for applying the current produced by said generating means to said indicating means to cancel the effect of the magnetizing component of the current through said primary winding.
Claim 11
Dependent Claim
31 words
A circuit as set forth in claim 7 in which said current indicating means is arranged to have a negligible effect upon the voltage across and current through said primary winding.
Claim 12
Dependent Claim
58 words
A circuit as set forth in claim 7 in which said generating means comprises an operational amplifier having an inverting input, an output, a first resistor connected between said input and output, a capacitor connected in parallel with said first resistor and second and third resistors connected to the inverting input and output of said operational amplifier, respectively.
Claim 13
Dependent Claim
39 words
A circuit as set forth in claim 7 in which said indicating means includes an operational amplifier having an inverting input and an output, a resistor, and means for connecting said resistor between said output and said inverting input.
References Cited (Backward Citations)
US2954523A
Cited
US3497793A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-17 | 1977-12-17 | 1978-06-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-17 | 1981-12-17 | 1982-06-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-17 | 1985-12-17 | 1986-06-18 | $7700.00 | Window Closed / Lapsed |