An Improved Calculation Method of High-frequency Winding Losses for Gapped Inductors

For the inductor with air gap, the magnetic field distribution in winding window is quite complex due to the air-gap fringing effects of the core. The Dowell model which is effectively used in the calculation of AC winding losses in transformers is no longer valid for gapped inductors. In this paper, the air-gap is equivalently replaced by surface current with certain geometry and current density distribution. And then, mirror-image method is utilized to deal with the boundary effect of magnetic core with high permeability. Most important, an novel analytic method is also proposed to improve the calculation speed and accuracy of high-frequency losses of round conductor within wider frequency range. Finally, the method proposed is verified by FEM (finite element method) simulation.It keeps very low error, which is less than 8%, when the ratio of wire diameter to skin depth reaches 4.5.

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