Minimum loss multilayer electrical winding for induction heating

Claim 1

A multilayer electrical winding disposed about an axis, comprising: at least two layers respectively including a first plurality of ampere turns in one of said layers and a second plurality of ampere turns in another of said layers; the ampere turns of each plurality being formed with a single conductor having radially of said axis a common thickness and longitudinally of said axis a common width; the common thicknesses and widths of said pluralities being selected to form respective monotone progressions in opposite directions as defined from the outside of said winding toward the inside thereof; with the common thicknesses thereof being such that for the first layer b i /δ has a value selected between 1.5 and 1.65; that for the second layer b i /δ has a value selected between 0.65 and 0.8, where b i is the layer thickness for the layer of rank i in said winding and δ is the effective depth of current penetration radially of said winding; and with the ratio w i /w 1 being selected between 1.2 and 1.45, where w 1 is the width of the conductor in the first layer, and w i is the width of the conductor of rank i; thereby to minimize resistance and eddy current losses in said at least two windings; with the conductors of two adjacent layers being connected at a common and adjacent end.