Optimal design and experimental validation of a Medium-Frequency 400kVA power transformer for railway traction applications

This paper presents the application of a Medium-Frequency (MF) Transformer design methodology applied to a 400kVA transformer intended for railway traction multi-voltage applications. First, a full-scale prototype operating at a moderate frequency (<;1kHz), based on a silicon-steel transformer and a Dual Active Bridge (DAB) has been developed and experimentally verified. Then, in order to reduce the volume and weight of the system, a second full-scale prototype has been designed based on a higher operation frequency (>;5kHz), a nanocrystalline transformer and a Series Resonant Converter (SRC), which has evolved towards a LLC Resonant Converter. A major volume and weight reduction (more than 85%) has been achieved between both designed transformers.