Optimal air gap design in high frequency foil windings

High frequency AC losses are normally induced in transformer and inductor windings due to skin, proximity, fringing and other AC effects. In addition, the winding structure greatly affects the distribution of losses within the windings. Air gaps are usually placed in the core of magnetic devices to support the high magneto motive force. Fringing fields can cause additional AC winding losses and care must be taken to minimize the additional losses. In this paper, the effect of air gap design on the induced losses is investigated. In particular, three air gap designs: the lumped, the discretely distributed, and the uniformly distributed air gap designs are investigated and evaluated. Both one-dimensional and finite element analyses are used to investigate the different design structures.