Patent ID: 7106162

Claim:
A current transformer, comprising: a Rogowski coil, having an opening at the center in which a conductor penetrates, comprising: a printed circuit board comprising at least 2N layers and further comprising at least 2N circuit board surfaces, whereby N is an integer greater than 2; a plurality of radial metal foils on each of 2N of the at least 2N circuit board surfaces, each metal foil extending along an axis that radiates from approximately the center of the opening; N windings, each winding formed by electrically connecting metal foils on a respective pair of circuit board surfaces with plated through holes penetrating the circuit board surfaces in a thickness direction of the printed circuit board; wherein a first winding is comprised of metal foils on a board top surface and a board bottom surface; N return circuit lines; wherein the return circuit lines are approximately circular metal foils with a center that is approximately the center of the opening; each of the return circuit lines being electrically connected with one of the N windings in series to form N winding—return circuit line pairs; wherein the N winding—return circuit line pairs are in turn connected in series with one another.