17-27In the article the possibilities of improving the adjustment properties and technical characteristics of electric rolling stock with collector traction motors are considered. Semiconductor devices can improve the smoothness of the traction motors start-up due to a more even voltage increase, smooth regulation of the field current in the traction and braking modes. Variants of simplified power circuits of eight-axis direct current electric locomotives with a minimum number of switching electrical devices have been developed, allowing to reduce weight and size of the equipment, increase the reliability of power circuits operations. Circuit solutions for protecting the wheelset of an electric locomotive from boxing and skidding by enhancing the traction motors field are considered. The role of semiconductor converters in the improvement of rolling stock with a combined and dual power is noted. The ways to improve the efficiency of electric braking by collector traction motors are listed. The necessity of using adaptive microprocessor control systems for semiconductor converters for expanding their functional capabilities and realizing optimal parameters of direct current rolling stock is noted.