Design of a 200 kW Medium-Frequency Transformer (MFT) With High Insulation Capability

This paper presents the design of a 200-kW medium-frequency transformer (MFT) based on low loss magnetic core (FINEMET® FT-3TL). Parallel-concentric winding structure is utilized to increase the current carrying capability and reduce the leakage inductance. Based on the parallel-concentric winding concept, a novel insulation structure with two-layer 3D printed bobbins is further proposed. The developed MFT achieves a power density higher than 19 kW/L. The electrical insulation system is tested at AC peak 14 kV voltage and DC 25kV voltage. In addition, the partial discharge test is conducted at AC 8.5kV peak voltage to ensure a partial discharge (PD)-free design. Finally, the MFT is applied to a medium voltage solid-state transformer (SST) to verify the design.