US 5,479,095 AGranted

Method and apparatus for measurement of AC and DC electrical current

AssigneePower Corporation of America

InventorsJan K. Michalek, Ebrahim B. Shahrodi

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Abstract

The present invention involves measurement of an electrical current by means of a current transformer having the current to be measured passing in an axial direction through the current transformer, and the voltage induced thereby in the windings of the current transformer are used to produce a first voltage. A Hall effect is used in series with the current transformer to produce a second voltage measurement corresponding to the current measured by the Hall effect sensor. When the two measurements agree to within a predetermined value (typically 5% of the root-mean-square current values measured by each sensor) then the current transformer reading is used as the more accurate. Otherwise, the Hall effect current sensor is used as the more accurate current measurement.

Claims5

Dependent claims

An apparatus for measuring electrical current comprising:

a) a current transformer having the current to be measured passing axially therethrough and producing a first voltage corresponding to a first measured value of said current;
and,
b) a Hall effect current sensor having said current to be measured passing axially therethrough, in series with the passage of said current through said current transformer, and producing a second voltage corresponding to a second measured value of said current;
and,
c) a comparison device receiving substantially simultaneously said first and said second voltages and selecting a selected voltage from said first and said second voltages, said device comparing said first and second measured current values wish each other and with a predetermined error limit, and said device selecting said first voltage if said measured currents agree to within said predetermined error limit, and selecting said second voltage otherwise;
and,
d) a switch directing said selected voltage to an output terminal.

4 more elements

Dependencies are inferred from the claim text.