Method and apparatus for detecting and compensating measurement errors due to transformer saturation in a meter
First Claim
1. A current measurement circuit comprising:
- an integrator circuit having a first input, and an output;
a first transformer including a first winding about a magnetic core, the magnetic core including an opening through which a conductor carrying measurement current passes, the first winding having a first terminal and a second terminal, the first winding configured to generate a first current based on a first flux in the magnetic core;
a second transformer including second and third windings, each of the second and third windings having a first terminal and a second terminal, the first terminal of the second winding coupled to receive the first current from the first terminal of the first winding, the second terminal of the second winding coupled to the second terminal of the third winding, the first terminal of the third winding coupled to the first input of the integrator circuit; and
a current measurement unit operably coupled to measure the current through the second winding of the second transformer;
wherein the output of the integrator circuit is operably coupled to provide an error current to the second transformer.
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Accused Products
Abstract
A current measurement circuit includes an integrator, first and second transformers, and a current measurement unit. The first transformer includes a first winding about a magnetic core. The magnetic core has an opening through which a current to be measured passes. The first winding is configured to generate a first current based on a first flux in the magnetic core. The second transformer includes second and third windings. The second winding is coupled to receive the first current from the first winding. The second winding has a terminal coupled to the third winding. The third winding is coupled to a first input of the integrator circuit. The output of the integrator circuit is operably coupled to provide an error current to the second transformer. The current measurement unit measures the current through the second winding of the second transformer.
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Citations
20 Claims
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1. A current measurement circuit comprising:
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an integrator circuit having a first input, and an output; a first transformer including a first winding about a magnetic core, the magnetic core including an opening through which a conductor carrying measurement current passes, the first winding having a first terminal and a second terminal, the first winding configured to generate a first current based on a first flux in the magnetic core; a second transformer including second and third windings, each of the second and third windings having a first terminal and a second terminal, the first terminal of the second winding coupled to receive the first current from the first terminal of the first winding, the second terminal of the second winding coupled to the second terminal of the third winding, the first terminal of the third winding coupled to the first input of the integrator circuit; and a current measurement unit operably coupled to measure the current through the second winding of the second transformer; wherein the output of the integrator circuit is operably coupled to provide an error current to the second transformer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 20)
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8. A circuit arrangement in a utility meter, comprising:
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a voltage measurement circuit configured to generate a voltage measurement signal; a current measurement circuit comprising an integrator circuit, a first transformer, and a second transformer, the integrator circuit having a first input and an output, the first transformer including a first winding about a magnetic core, the magnetic core including an opening through which a conductor carrying measurement current passes, the first winding having a first terminal and a second terminal, the first winding configured to generate a first current based on a first flux in the magnetic core, the second transformer including second and third windings, each of the second and third windings having a first terminal and a second terminal, the first terminal of the second winding coupled to receive the first current from the first terminal of the first winding, the second terminal of the second winding coupled to the second terminal of the third winding, the first terminal of the third winding coupled to the first input of the integrator circuit; and a current measurement unit operably coupled to generate a current measurement signal by measuring the current through the second winding of the second transformer; an analog-to-digital conversion (A/D) circuit operably coupled to receive the voltage measurement signal and the current measurement signal and generate digital voltage and current measurement signals therefrom; a processing circuit configured to generate energy consumption information based at least in part on the digital voltage and current measurement signals. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A current measurement circuit comprising:
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an integrator circuit having a first input and an output; a first transformer including a first winding about a magnetic core, the magnetic core including an opening through which a conductor carrying measurement current passes, the first winding having a first terminal and a second terminal, the first winding configured to generate a first current based on a first flux in the magnetic core; a second transformer having a non-magnetic core that extends around the conductor, and including second and third windings, each of the second and third windings having a first terminal and a second terminal, the first terminal of the second winding coupled to receive the first current from the first terminal of the first winding, the second terminal of the second winding coupled to the second terminal of the third winding, the first terminal of the third winding coupled to the first input of the integrator circuit; and a current measurement unit operably coupled to measure the current through the second winding of the second transformer; wherein the output of the integrator circuit is operably coupled to provide an error current to the second transformer. - View Dependent Claims (17, 18, 19)
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Specification