The paper deals with a drive system of experimental fully electric airplane VUT 051 RAY with rated power 55 kW. The requirements on accumulator capacity and its weight were defined according to a precisely specified flight profile. The whole design process of traction inverter is presented. Drive train system of electric airplane was completely tested, before its final installation into fuselage of airplane. Measured parameters gained by testing are presented too. Finally, the results of first flight are presented.