Integration of Leakage Inductance in Tape Wound Core Transformers for Dual Active Bridge Converters

Dual Active Bridge (DAB) converters are nowadays used in applications such as automotive and general energy storage interfaces, where efficient and compact isolated bidirectional DC/DC converters are required. The heart of this converter is a transformer which, in some designs, may include the required inductance to shape the current and control the energy transfer. This paper shows that for these designs, tape wound cores, usually made of amorphous or nanocrystalline materials, are not the best core option due to leakage flux which is orthogonal to the lamination layers. This flux increases losses in these types of cores. Solutions are proposed to overcome this significant drawback. Analysis developed in this paper is validated by experimental results, which show that core losses due to orthogonal flux in a tape wound core transformer can be reduced more than 6 times if an adapted leakage layer is used instead of a regular one.