The paper presents a short description of electric traction systems used on electrified railways in the world. For the proposed three-phase system of electric traction the authors consider features of operation of 6-pulse bridge rectifiers in full-phase and open-phase modes. The paper also demonstrates principal schemes and time diagrams that explain operation of 6-pulse bridge rectifiers in the open-phase mode at connection of valveside windings of a transformer «star» / «star» and «star» / «delta». On the basis of executed research the authors present relations that connect voltages, currents and power of 6-pulse bridge rectifiers in the open-phase mode for controlled and uncontrolled transformers.

The paper proposes a conceptual approach to economic efficiency substantiation of three-phase alternating current system of electric traction in comparison with one-phase alternating current system of electric traction. It is based on quasi-optimal values of indicators of electric traction system that are necessary for feasibility study and assessment of integral criterion of efficiency, for which, in turn, it is necessary to compare systems by reduced expenditures. Saving of reduced expenditures should also consider out-of-transport effect that is very important for system effect of interaction between railway transport and other enterprises.

At development of common concept of current collection for three-phase traction power supply system there is the need to select and substantiate main design parameters of catenary suspension. For this purpose, the authors have carried out analytical calculations and developed a numerical mathematical model that allows assessing catenary statics and it’s dynamics in interaction with current collector. On the basis of results of modeling, the authors have substantiated and selected all the required parameters. In particular, they have determined the permissible speed of trains and maximal length of catenary spans.