DC=TO-THREE-PHASE-AC VOLTAGE CHANGER (OPTIONS) Russian patent published in 1996 - IPC

FIELD: converter engineering; devices incorporating non-regulated dc voltage supply, dc voltage changer, LC filters at changer input and output, and three-phase bridge voltage inverter with forced thyristor switching assemblies and designed for power supply and frequency-starting of heavy-power induction motors. SUBSTANCE: there are two different circuit arrangements for attaining desired effect. Common for both and rather essential are the following features: double-stage switching of main thyristors of inverter, forced switching unit of isolating thyristors ensuring its off-line operation, use of switching voltage capacitor built around capacitor of dc changer input filter as additional charging source which provides for pre-charging switching capacitor by means of auxiliary thyristors, and voltage across it independednt of varying voltage in inverter power circuit, individual action on main thyristors. EFFECT: improved forced switching assembly of main thyristors of inverter to raise high switching stability of inverter at its constant output current with varying frequency and voltage at inverter output and wide voltage regulation range for inverter power circuit without using additional source of switching capacitor charge. 2 cl, 4 dwg