Modeling Litz-wire winding losses in high-frequency power inductors

The parasitic effects in stranded, twisted, and Litz wire windings operating at high frequencies are studied. The skin and proximity effects that cause the winding parasitic resistance of an inductor to increase with the operating frequency are considered. An expression for the AC resistance as a function of the operating frequency is given. The measured and calculated values of the inductor AC resistance and quality factor are plotted versus frequency and compared. The theoretical results were in good agreement with those experimentally measured.