Electro-Thermal Co-Design of a Cooling System-Integrated High-Frequency Transformer

This paper presents electro-thermal design optimization of a high-frequency planar transformer with an integrated thermal management system involving a liquid-cooled chamber for combined core and winding cooling. The designed transformer is for a 10 kW, 600V to 800 V, 1 MHz dual-active-bridge converter, working as the dc-dc stage of high power-density on-board electric vehicle chargers. Effect of design variables like number of turns of the transformer and cooler height on the transformer's electrical parameters such as leakage inductance, ac resistance and parasitic capacitance is estimated. The dependence of converter efficiency on these parameters is estimated using simulations and analyses and potential trade-offs of the design are investigated. Similarly, thermal modeling is used to characterize the thermal performance of different designs, evaluated on the basis of the required coolant temperature to maintain the transformer winding and core at a specified temperature. Based on a combination of the preceding analyses, optimal designs are identified which simultaneously ensure good electrical and thermal performance.