Layered foil as an alternative to litz wire: Multiple methods for equal current sharing among layers

Litz wire is useful for high-frequency power but has high cost, limited thermal conductivity, and decreased effectiveness above 1 MHz. Multiple parallel layers of foil have the potential to overcome these limitations, but techniques are needed to enforce current sharing between the foil layers, as is accomplished by twisting in litz wire. Four strategies for this include already known techniques for interchanging foil layer positions, which are reviewed, and three new approaches: 1) balancing flux linkage by adjusting spacing between layers, 2) using capacitance between layers to provide ballast impedance, and 3) adding miniature balancing transformers to the foil terminations. The methods are analyzed and their scope of applicability is compared.