Electric energy meter having a mutual inductance current transducer

Claim 1

An AC electric energy meter having an electronic measuring circuit processing analog signals responsive to current and voltage components of an alternating current electric energy quantity supplied by conductors of a power line distribution system and to be measured for producing electronic signals representative of quantized amounts of electric energy consumption, said meter comprising: a housing adapted for series connection of said meter with at least two of said power line distribution system conductors carrying separate current flows of said electric energy quantity to be measured; a voltage sensing transducer connected in parallel with said power line distribution system conductors for producing a voltage responsive analog voltage signal proportional to said voltage component; current sensing transducer means comprising first and second current conductors each connected serially with one of said power line distribution system conductors for series connection with each of the separate current flows of said current component, each of said current conductors effectively forming a single turn primary winding for producing magnetic flux variations responsive to the magnitude and rate of changes of the separate current flow therein; said current sensing transducer means further comprising secondary winding means comprising first and second toroidal windings each separately receiving one of said current conductors, each of said toroidal windings being wound on separate non-magnetic cores so as to include multiple turns each wound with a substantially rectangular cross section having a longer side substantially parallel to the single turn primary winding formed by said current conductors with the center openings of said toroidal windings being each mounted on separate non-magnetic cylindrical mounting sleeves carried by said current conductors so that said toroidal windings are inductively coupled to said magnetic flux variations of the associated current conductor through an effectively non-magnetic air gap space, and said toroidal windings further comprising lead wire conductors connected so that said secondary winding means produces a current responsive analog voltage signal linearly proportional to the sums of the time derivatives of the separate current flows in each of said current conductors throughout a ratio of combined current variations of at least four hundred to one with both of said voltage and current responsive analog voltage signals being effective for connection to high impedance and low level signal inputs of said electronic measuring circuit.