Circuitry ascertaining start of switch-over time - connects outputs of two OR=gates and via AND=gate for star points of antiparallel thyristor bridges of rectifier or inverter

摘要

An inverter circuit for supply of electrical motors has a thyristor based bridge network (2) arranged in two groups (GR1, GR2). Opto-couplers provide signals to a circuit that allows determination of the start of the switching period. The opto-couplers connect Cu a pair of logic inverters (3,41) providing inputs to a logic circuit (8,10,14,15) supplied by a flip flop (7) set and reset by OR-gate signals (4,6). The OR-gates respond to the firing signals applied to the thyristors. The output gate (15) signals the start of the switching period. ADVANTAGE - Fastest possible switchover is surely detected currentless state.