The paper presents a refined method for calculation of critical currents flowing through thyristors of a thyristor-reactor switching device aimed at voltage regulation at traction substations on railways electrified with direct current. The method considers overcurrent of thyristors in a dynamic mode of operation that occur in result of discharge of accumulated energy in inductive elements of the device. The authors have calculated critical currents flowing through thyristors of the switch being a part of the perspective converter transformer TRSNP-12500/10 that has a 14 % range of voltage regulation.

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.

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