To guarantee good efficiency, all transformers of the WE-FB series are optimized for a very low leakage inductance. High leakage inductances cause high voltage spikes on the switch and therefore need to be reduced by a snubber network. The losses generated in the snubber are related to the height of the voltage spike. This means lower leakage inductance causes a lower voltage peak and therefore lower losses. The low leakage inductance is achieved by full flat layers and split windings. Wire is selected to fill the layers. When needed, multiple strands are used to fully fill the layer. As an example, Picture 1 shows the winding build of 750311675. With this structure, the typical leakage inductance of 760311675 is 130nH at 100kHz.