The main drives of the excavator EKG-8 are made according to the G-D system and have a control scheme based on the electromachine and magnetic amplifiers (scheme with EMU-PMU cascade). This scheme, as tests have shown, has a number of drawbacks.At present, in connection with the transition to mass production of excavators EKG-8 there is a need to develop simpler and better automatic control schemes. Promising in this respect are control schemes of electric drives of the excavator built on the basis of magnetic amplifiers (MU). When developing such schemes, it is very important to correctly build the excitation circuit of the generator, as it largely determines the structure and parameters of the control circuit as a whole and, ultimately, the properties of the drive.