Analysis of winding losses in high frequency foil wound inductors

The design of high power and high frequency foil wound inductors is not a straightforward task. At high frequencies, additional losses occur within the foil windings due to the eddy currents induced by skin, proximity, fringing and other AC effects. In addition, the winding structure greatly affects the distribution of losses within the windings. In this paper, the various loss mechanisms of a foil winding are analyzed and quantified. Both analytical and finite element analysis tools are utilized to investigate and understand the different loss mechanisms. The results show a strong correlation between the current and field distributions within the windings where the current is always attracted to the high field regions. By shaping and controlling the field distribution in a given design, the current distribution can be improved which results in an improvement in the winding losses