Litz wire in the MHz range: Modeling and improved designs

Abstract

Although conventional litz-wire design and modeling indicates that it has little benefit for frequencies much beyond where skin depth equals the strand diameter, we investigate this region of operation more closely, including the effect of the effective complex permeability of the winding region with different winding and inductor geometries, and the effect of the configuration of strands within a litz bundle. We show that the benefit of litz wire extends to higher frequencies than was indicated by previous models with some field geometries and show that a “hollow” litz wire structure in which strands are confined to the outer perimeter of a dielectric core is superior to conventional litz in many high-frequency designs.