Power inductors made by powder metallurgy

Power inductors to replace those constructed from laminations may be made by powder metallurgical methods. High-quality atomized iron powder is first oxidized in potassium dichromate solution and then annealed at low temperature after pressing. The low permeability of the material necessitates some changes in the design of the inductor to accommodate extra magnetic material, but these are compatible with powder die design. A gap in the magnetic circuit reduces the harmonic distortion to levels well below the limits of IEC 82 [1]. The work is based on studies of small toroids which are described by a simple theory.