Utilizing stray capacitances of a litz wire

In power electronics applications, litz wire is widely used for reducing ohmic losses due to skin- and proximity effect eddy currents. Litz wire also introduces stray capacitance that can be utilized in the design of such devices as niters and inverting, matching and balun transmission line transformers (TLTs). This paper focuses on a set of solutions that is obtained through finite element modeling for predicting the per unit length capacitance as a function of the fractional thickness of the strand insulation, its relative permittivity, and the number of strands used in a litz wire conductor. A simple statistical approach is used to account for the unknown distribution of strand position along the lengths of litz bundles, and measured results of prototype samples are presented. Prototype structures are built using litz wire and their frequency dependent characterization is presented.