Comparison between numerical and analytical methods of AC resistance evaluation for Medium Frequency Transformers: Validation on a prototype

In the future, Medium Frequency Transformers (MFT with a frequency range 5 kHz to 100 kHz) will be major components in DC-DC converter applications, for both Medium Voltage Direct Current (MVDC) and High Voltage Direct Current (HVDC) networks. Importantly, the corresponding power losses should be accurately calculated in order to reach performance targets (very high efficiency). This paper reviews the most known analytical models which are used to calculate the medium frequency resistance for several winding technologies. In order to qualify these models in a future design flow, we compare the analytical model results with measurements and 3D finite element (3DFE) electromagnetic simulations. The adopted design flow-chart has been tested on a 17 kHz - 180 kVA prototype transformer that will be used in a Dual Active Bridge (DAB).