A Fourier-Based Semi-Analytical Model for Foil-Wound Solid-State Transformers

Abstract

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Hybrid Foil-Litz Windings for Highly Efficient and Compact Medium-Frequency Transformers

“…3; the geometrical quantities are summarized in Table 1. Similarly to [31], the FEM model is analyzed by a second-order discretization, using triangular and rectangular elements in the nonconducting and conducting regions, respectively; the mesh is refined in the conductor regions using at least three layers of elements within the H penetration depth. To reduce the mesh size, the insulation distance between the turns is neglected.…”

“…The analyses on standard foil windings presented in [15], [23], [31] show that D hv,c introduces in H a component perpendicular to the foil, with magnitude H ⊥ , which leads to a strong concentration of current in the edges of the conductor. This is evaluated considering the case D hv,c = 30 mm and f = 20 kHz: the contour plot in Fig.…”

“…4 shows that H ⊥ is 1.7 times the maximum magnetic field intensity in the ideal case with D hv,c = 0 mm, i.e., H 0 = N t I/h e , where I is the current in the turn and h e the electrical height of the winding. This leads to a peak in the current density magnitude J that is more than 10 times the case when f = 0 Hz, i.e., J dc = I/h f w f [15], [31].…”

Mitigation of Circulating Currents in Parallel Foil Windings for Medium Frequency Transformers

“…Foil conductors, on the contrary, show improved effective conducting cross-section area and heat dissipation, enabling higher power density designs, and reduced manufacturing cost. However, the frequency-dependent losses in foil conductors are higher due to the current concentration in the corners of the foil crosssections [3]. This phenomenon is eliminated in litz windings by twisting or trans-positioning [4].…”

Design Trade-Off Analysis of Dry-Type Medium Frequency Transformers with Parallel Foil Windings

“…Although a comparably inexpensive choice is foil conductors, using foil in higher frequencies requires a careful design approach to avoid excessive ac losses. The current density concentration in the corners of rectangular cross-sections of foils brings additional eddy loss in the windings [5]. While twisting and trans positioning techniques are used in litz windings to reduce the proximity effect in medium frequency operating points, these techniques are not practical due to the high aspect ratio of the foil conductors.…”