The analysis was made on the assumption that motor efficiencies were optimal for set load torque characteristics. Linear relationship were assumed to obtain in the motor magnetic circuit, while neglecting the extra losses due to conventional supply and to friction and windage losses. Standard equivalent circuit of induction motor was used to calculate the influence of fundamental and higher harmonics in assessing invertor impact on control laws. The calculation of rotor losses took the deep bar effects into account. It showed out that, in invertor supply, control laws for induction motors retain the same form as in power feeding from sources with a sinusoidal voltage.