The Design and Construction of Transformers for a 50 kW Three-Phase Dual Active Bridge DC/DC Converter

Fast charger stations are one of the key components towards more electric transport systems. The size and cost of high power chargers are demanding more improvement while a high level of efficiency are required. Consequently, the main methodology to achieve these specifications is to increase the system operating frequency, if the losses in the magnetic materials and semiconductors can handle that. A 50 kW compact and efficient fast charger station is designed and constructed in Chalmers University of Technology, Sweden. The charger structure is an active three- phase PWM converter followed by a three-phase dual active bridge DC/DC converter. The SiC high-power modules and nanocrystalline magnetic materials are utilized to achieve a higher frequency operating point. Three single-phase Y-Y connected transformers are are designed, constructed and partially verified in the circuit in which the leakage inductance of the transformers are used as the energy storage devices. Design considerations as well as simulation and measurement results are presented in this paper. The maximum error between the calculated, simulated and measured values is less than 2.5 %.