OPTIMAL AIR-GAP DESIGN IN HIGH-FREQUENCY FOIL WINDINGS

High-frequency ac losses are normally induced in transformer and induc tor windings due to skin, proximity, fringing, and other ac effects. I n 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 magnetic motive force (mmf), Fri nging 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 will be investigated. In particul ar, three air-gap designs-lumped, discretely distributed, and uniforml y distributed-will be investigated and evaluated. Both one-dimensional (1-D) and finite-element analyses (FEA's) are used to investigate the different design structures.