No abstract

In this paper, a systematic procedure is presented, how to predict the AC resistance of litz-wire windings considering air gap fringing fields. For this purpose, an equivalent complex permeability model is derived for hexagonally packed wires. It is shown, how finite element method (FEM) can be used to determine the real as well as the imaginary part of the complex permeability with the copper filling factor as a parameter. A further FEM-model is deduced to describe the air gap fringing fields of gapped inductors. Accordingly, the exact proximity losses of the litz-wire winding are determined correctly and the AC resistance of practical inductors can be predicted over a wide frequency range with high accuracy. This offers the opportunity to optimize such components. Finally, the influence of various parameters on the copper losses is investigated and verified by means of experimental data drawn from impedance measurements.

Improving power density is a permanent challenge of R&D in power electronics. A survey of modern power electronic circuits shows that further optimization has to be based on the passives and particularly on the inductive components. State-ofthe-art inductors (e.g. in LC, LCL and dU/dt filters) contribute a lot to space, weight, losses and cost as well. In this paper, a new generation of power inductors is presented. The thermal management of these components has been optimized using FEM and extensive thermal measurements. Thus, much higher electrical current densities have become possible at the same hotspot temperature, which is finally equivalent to higher energy density and smaller component size.

In this paper, a practical method is presented, how to adjust the inductance curve of a nonlinear (saturable) inductor with respect to a desired shape. For these purposes, a nonlinear model was developed based on finite element method (FEM). It is shown how a highly efficient construction with low stray fields and maximum package density can be achieved. Different prototype inductors were realized to illustrate the practical capability for active power factor correction (PFC) applications. All simulation is verified by means of experimental data drawn from electrical measurements.

A practical method is presented: how to adjust the inductance curve of a nonlinear (saturable) inductor with respect to a desired shape. For this purpose, a nonlinear model was developed based on finite element method (FEM). It is shown how a highly efficient construction with low stray fields and maximum package density can be achieved. Different prototype inductors were realized to illustrate the practical capability of photovoltaic (PV) inverters as well as active power factor correction (PFC) applications. All simulations are verified by means of experimental data drawn from electrical measurements.