With the development of power electronics, variable frequency drives (inverters) became common in the driving and speed control of industrial induction motors. These however do not provide lossless control since in the motor appears an injurious higher voltage as well the current and flux harmonics caused by the switching of the voltage. The dissertation presents the control algorithms which can reduce these losses of induction motors fed by simple inverters with additional switching. The time of additional switching must provide the minimum of harmonic losses for a given value of the motor fundamental voltage. The method of calculating the times of the additional switching is presented. The different control algorithms of inverter are elaborated, checked by simulation and implemented on a real device, manufactured by Procon. The comparison of the computations results of simulation with the measurements showed that the actual voltage-time functions, their spectra and values of motor harmonic losses are not far one from each other.