| 摘要 |
PROBLEM TO BE SOLVED: To detect short-circuiting in direct-current power supply and provide protection therefrom by interrupting gate signals of a plurality of self-arc- extinguishing elements when both of gate reverse voltage detectors for the self-arc-extinguishing elements, which are alternately on/off-controlled, output zero. SOLUTION: The outputs (1), (2) of gate reverse voltage detectors RVGKP, RVGKN for GTO thyristors GP, GN are connected with a NAND circuit NAND 1, and the output (3) of NAND1 is connected through an inverter circuit INV with an OR circuit OR that interrupts gate start signals. If either of the GTO thyristors GP or GN is damaged for some reason, a direct-current power supply short circuit that brings both GP and GN in conduction occurs. The accident is detected by NAND1, and a start signal to the gate stop circuit GST is interrupted by the inverter circuit INV through the OR circuit OR. That is, a gate signal to other phases is stopped, and the influence of the accident is thereby prevented from spreading. |
