Frequency-dependent inductance and winding loss model for gapped foil inductors

Abstract

For comprehensively optimizing high-frequency foil wound inductors, the calculation of the increased inductance and the additional eddy current losses due to a two-dimensional fringing field caused by air gaps in the center leg is mandatory. This paper proposes an analytical model to accurately calculate the inductance and the additional eddy current losses in gapped inductors with foil windings. The analytical field expressions are combined into closed form conduction loss and inductance formulas and are verified by measurements. The frequency dependency of the inductance due to the shielding effect of the foil conductors is discussed.