Variable inductor modeling revisited: The analytical approach

This paper presents the modeling of variable inductors (VI) following an analytical procedure. Usually, in a VI a dc magnetic flux is injected into the structure in order to provide a bias level that allows for magnetic permeability modulation. The ac magnetic flux is superposed to this dc level, thus making it possible that a variable inductance can be seen from the ac windings. Under the assumption that the ac magnetic flux amplitude is much smaller than the bias level, it is possible to analyze the VI by applying the superposition principle to the equivalent reluctance circuit of the structure. This procedure is illustrated in this paper for a double-E based VI. The proposed methodology is supported by both simulation and experimental results for a particular VI.