REGULATED-POWER DC-TO-THREE-PHASE INVERTER Russian patent published in 1998 - IPC

FIELD: converter engineering; power supply to and frequency starting of heavy-power induction motors; power supply to heavy-power synchronous motors and variable-frequency and variable-voltage resistive-inductive loads. SUBSTANCE: inverter has variable DC voltage supply, LC or C ripple filter, three-phase bridge-type voltage switch, forced switching units of main thyristors. Output current of inverter is maintained constant (at rated level) in case of its output voltage and frequency fluctuations; switching capacitor recharging circuit dispenses with filter capacitors; under rated operating conditions of inverter, additional power supply of switching capacitor does not consume power from supply mains. Two circuit arrangements (versions) are proposed. Common and essential for both of them is introduction of additional recharging circuit affording independent operation of forced switching unit in case of supply voltage fluctuations; two-step switching of main thyristors; introduction of isolating thyristors switch in forced switching unit of main thyristors ensuring off-line operation of unit; oscillatory recharging of switching capacitor; individual action on main thyristors of switch. EFFECT: simplified circuit arrangement; reduced switching loss. 2 cl, 2 dwg