Forward biased thyristor over voltage protection cct. - has non-linear resistance element acting as over voltage sensor between anode and gate

摘要

The overload protection circuit for forward biased thyristors consists of two non-linear elements whose resistances change from high to low values. The first element acts as an overvoltage detector and is coupled in series with a protective resistor which limits the current through the same. The series combination is coupled by a capacitor across the main thyristor requiring protection. The capacitor is bridged by another resistor which stabilises the first element. The second non-linear element connects the main thyristor gate to the junction between the capacitor and the first protective resistor. In normal operation a voltage divider or an attenuator keeps the main thyristor anode/cathode voltage at a given value.