Design and Testing of a Compact Dry Insulated Medium Frequency Transformer Prototype for Medium Voltage Applications

Input series output parallel modular converters as a Solid-State Transformer for interfacing Medium Voltage to Low Voltage requires many compact insulated medium frequency transformers. High efficiency and power density for such transformers are the key drivers for applications in datacenter and EV charging. Combining high compactness and low losses in a medium voltage insulated medium frequency transformer is challenging when the insulation medium is air. Apart from the electromagnetic components, the insulation design related to the termination plays a huge volume in such MV class MFT. In this paper, the design, prototyping and testing of a cast resin 12 kV class insulated medium frequency transformer with 99.5% efficiency and a power density higher than 5kW/l including terminations is presented. Dielectric performances are demonstrated experimentally at rated conditions. An accurate calorimetric based loss measurement method and a full load test procedure are also presented.