Litz Wire Configurations for Charging Applications: A Field Study

Inhalt:
This paper shows various optimisation approaches for high frequency litz wire designs, used in the transformer of a resonant 22 kW DC stage for chargers. For this purpose, designs are made with different wire diameter for high cost versus low cost, alternative conductor materials, bundle variants and higher filling factor. Possibilities and complexity of litz wire designs are shown and a brief insight in eddy current losses and the possibility to predict them in a litz wire is given. The efficiency of the various transformer setups is focussed on experimental validation. A high power measurement routine is implemented to compare with low power measurements of a conventional impedance-analyzer. As a result of the paper, the different litz wire designs are compared in cost, weight, complexity and efficiency.