METHOD AND DEVICE TO PREVENT UNCONTROLLED FIRING OF VALVE THYRISTORS

摘要

METHOD AND DEVICE TO PREVENT UNCONTROLLED FIRING OF VALVE THYRISTORS A device to prevent uncontrolled firing of valve thyristors, designed to carry out the method according to the invention for preventing uncontrolled firing of valve thyristors, and comprising an anode current monitor connected in the power circuit of a thyristor or a group of thyristors with a voltage divider placed in parallel with this thyristor or group of thyristors. The anode current monitor is connected to a timing circuit comprising a time-variable positive anode voltage bias unit whose input is electrically coupled to the center tap of the voltage divider, and a delay unit whose input is connected to the anode current monitor and output is connected to a second input of the time-variable positive anode voltage bias unit. The delay time of the delay unit is dependent on the amplitude and rate of drop of the anode current. The delay unit is meant to ensure a constant positive voltage bias over a portion of a time interval, starting from an instant when the anode current drops below a specified value. The output of the positive bias unit is electrically coupled to a circuit intended to control the thyristor or group of thyristors by means of a switch operated by a specified switching voltage.