Bus bars of complex cross section were designed in order to achieve desirable characteristics for use with high power switching devices. High permeability material was introduced between the copper bus bars, to increase non-linear rise of the bars' resistance with frequency. Micro genetic algorithm (μGA) was used to search for the most suitable combination of parameters. The main goal was to design bus bars with adequately adapted resistance and inductance at 10 kHz and 50 Hz simultaneously. The frequency dependant resistance and inductance were calculated utilizing 2D FEM software.