Design of series inductances for high-power dc-dc converters

Galvanically isolated dc-dc converters require a certain series inductance in the ac link. Since it complicates the design process, the stray inductance of the transformer might not be designed sufficiently. This paper designs dedicated inductors to be operated in the medium-frequency ac link of a high-power dc-dc converter rated for 5 MW to increase the effective stray inductance. Different core materials are evaluated in terms of efficiency, power density and costs for an operation frequency of 1 kHz. Comparatively, air coils are designed for this particular application. Finally, the inductors are related to the medium-frequency transformer operated in the same converter in terms of weight and volume. The design procedure and material comparisons can be very well extended to other applications.