In this final paper, an idling test of an asynchronous motor powered by a frequency converter was performed, with the aim of determining the losses incurred. The second chapter discusses asynchronous motors in general and their basic characteristics, such as the principle of operation, the design of asynchronous motors, and the construction itself. The third chapter discusses frequency converters, with special emphasis on indirect frequency converters with a DC voltage intermediate circuit that was used in this experiment and sinusoidal PWM modulation that controls the commutator switches of this indirect converter. The fourth chapter deals with the description of the idling test of an asynchronous motor, i.e. what can be determined from the idling test, and the experimental determination of idling losses.