1,114,425. Thyristor circuits. LICENTIA PATENT - VERWALTUNGS - G.m.b.H. 5 July, 1965 [3 July, 1964], No. 28464/65. Heading H3T. [Also in Division H2] In a circuit for supplying a load with three phase current from a D.C. source via six power thyristors and inductances, each thyristor is shunted by an auxiliary thyristor in series with a quenching capacitor, and two resistors are provided for charging the capacitors in the two halves of the circuit. In Fig. 5 the power thyristors 1, 13, 14, 15, 16, 17 have their auxiliary thyristors 5 and quenching capacitors 6 in series with diodes 5b. The capacitors resonate with inductors 8 and the presence of resistors 10, 18 and diodes 5b, 7b ensures that the capacitors can charge up to the full supply voltage U, and that leakage through the auxiliary thyristors 5 when the power thyristors are on for a long time will not reduce the capacitor voltage too much for efficient quenching. The supply of charging current through resistors 10, 18 is further controlled by extra thyristors 7a and diodes 12a. The three-phase pulsed output is taken via centre-taps of transformers to points R, S, T. The voltage across a-b or a-c can be used to check that the three capacitors are charged sufficiently in the reverse direction. The arrangement of the capacitor, auxiliary thyristors, diodes, resistor and inductance may be varied (Figs. 1-4, not shown). An extra resistor (10) may be present for aiding charging of the capacitor in the opposite half-cycle to charging through resistor 9. The load may be a motor.