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In this work, a process for automated FEM based transformer design is presented. The entire design procedure is performed with the open source toolbox FEMMT from the department LEA at Paderborn University. In terms of providing the required functionality, an approximation for stranded wires, a method for inductance calculation from field solutions, core loss models and an analytical reluctance model have been contributed to the toolbox. All functions are directly integrated into the Git repository. Further, an exemplary design process for a transformer with dedicated leakage path is run through. By applying goal parameters, such as the transformer ratio, mutual and stray inductance as well as the current wave forms, a loss optimization for a wide input feature space is shown. Combining fast preliminary analytical and precise FEM based calculations, enables a fast investigation of a certain feature space. Moreover, a combination of initial global and subsequently local grid search approaches leads to a self converging optimization.To validate the designed magnetic component, a laboratory prototype of the designed integrated transformer is assembled and put into operation in a Dual Active Bridge (DAB) converter. The bidirectional DAB is a part of an Uninterruptible Power Supply (UPS), that is capable of smart grid actions, by feeding back power to the mains. With the prototype converter a peak-efficiency of more than 96 % is achieved.