Zero current state of converter - is generated with controllable main rectifiers in three-phase bridge connected to load

摘要

During normal operation firing pulses with a duration of over 60 electrical degrees are passed to the main rectifiers. The converter receives at first a command signal to reduce the current to zero and subsequently the firing pulses for the main rectifiers are shifted in the direction of the highest inverter supply. A zero current message is formed which introduces further measures in particular the quenching of the firing pulses for the main rectifiers. At the earliest value of the command signal for reducing the current, the duration of the firing pulses for the main rectifiers is reduced to a value under 60 electrical degrees.