SERIES CIRCUIT OF THYRISTOR WITH OVERVOLTAGE PROTECTIVE FUNCTION

摘要

PROBLEM TO BE SOLVED: To provide a series circuit of a thyristor with an overvoltage protective function which does not operate an overvoltage protective function due to an erroneous detection even when an operating state arises that a load current is intermittently supplied. SOLUTION: The series circuit includes the plurality of thyristors 11 with overvoltage protective functions connected in series through series reactors 12 and respectively having snubber circuits 13 and 14, forward voltage detecting circuits 16 for detecting voltages respectively between main electrodes of the thyristors 11 with the overvoltage protective functions and gate control means 2 for supplying gate pulses to the thyristors 11 with the overvoltage protective functions in accordance with an ignition timing signal from a phase controller 3. The gate control means 2 outputs a protection stop command for stopping a device when any of the forward voltage detecting circuits 16 detects voltage of a prescribed threshold value or higher until a first prescribed time elapses after the phase controller 3 generates the ignition timing signal and during a period in which a second prescribed time elapses after the supply of the gate pulses. COPYRIGHT: (C)2010,JPO&INPIT