Abstract: Converter inverters, such as are used in the operation of alternating current machines, have turn-off reverse-conducting GTO thyristors in the bridge arms. Parallel to each GTO thyristor there is provided a series circuit composed of a turn-off load-shedding capacitor with a turn-off load-shedding diode. The common junction points of the respective turn-off load-shedding capacitors and diodes are connected in series to a choke via at least one capacitor load-shedding diode. The inductance of the choke is 2 to 3 times as large as the inductance of the circuit. The reverse-conducting GTO thyristors are directly connected in series, without the series connection of a choke. There thus arises a damping circuit of the GTO thyristor, which is very simple and, at the same time, feed back ring-around energy.

Abstract: A static converter circuit has a voltage summing transformer (Tr-Tr13) with several part transformers (Tr1-Tr13) the static-converter-side winding of which are connected via one four-quadrant actuator each to a direct-voltage link circuit. The four-quadrant actuators are single-phase bridge circuits with one GTO thyristor each and a diode, which is antiparallel thereto, per bridge branch. The static-converter-side windings of the part transformers can be short circuited in each case by means of an alternating-current circuit breaker with antiparallel-connected thyristors. Each part transformer has a separate core. The power-system-side windings of the power transformers are connected in series and are connected at their ends to a railroad power system with 162/3-Hz. The direct-voltage link circuit is connected via power-system-commutated static converters and a static converter transformer to a national power system with 50 Hz.