COMMUTATION FAILURE PREVENTING CIRCUIT OF CONVERTER FOR LINEAR THYRISTOR MOTOR

摘要

PURPOSE:To prevent the commutation failure of a thyristor switching unit by applying the output of a current transformer for detecting the commutation capacitor current to a transistor connected in parallel between the gate and the cathode of a thyristor corresponding to the thyristor switching unit. CONSTITUTION:When a gate signal is applied to a thyristor 4b in case that the voltage of a commutation capacitor 6 is charged in polarity as shown and a thyristor 4a is conducted, the thyristor 4b is conducted and starts commutating. At this time a voltage similar to the current flowing through the capacitor 6 is applied by a current transformer 11 to the base electrode of a transistor 14. Since the gate and the cathode of the thyristor 4a is shortcircuitted during the commutation period in this manner, the gate signals of the thyristors 4a, 4b are not superposed during the commutation period, thereby preventing the commutation failure.