High-Frequency Transformer Review and Design for Low-Power Solid-State Transformer Topology

The objectives of this paper are to review and compare the design of high-frequency transformers (HFTs) for low-power solid-state transformer (SST) converter topologies. Two different HFT design examples, a 25 kHz, 5 kVA, 440/110V amorphous shell core transformer, and a 100 kHz, 350 VA, 130/117V nanocrystalline toroid core transformer, are described. Nanocrystalline alloy magnetic core HFT yields a higher efficiency than that of the amorphous alloy magnetic core HFT at 100 kHz or higher frequencies, while at 25 kHz their efficiencies are similar but the amorphous magnetic core HFT is cheaper than the nanocrystalline magnetic core HFT for the same power ratings. The fabrication for the two HFTs and their main operational features are presented and discussed.