| 摘要 |
PURPOSE:To prevent an optical thyristor from being broken, by connecting together optical fibers extended from a control unit and optical fibers extended from forward voltage protecting circuit so as to limit a total number of the optical fibers in use to the smallest possible level. CONSTITUTION:An optical firing signal from a control unit 2 is sent to gates of optical thyristors LS1-LS2 through an optical fiber Y-X. While a thyristor converting device is operated, a certain thyristor is in some cases turned off due to an abnormal phenomenon. In order to turn on the thyristor immediately in such a case, a forward overvoltage protecting circuit D corresponding to the thyristor is energized to send an optical firing signal through an optical fiber Z-Y. This structure, as compared with a structure wherein a refiring signal is sent from the control unit 2, permits reducing the number of optical fibers and preventing, owing to quick generation of a refiring signal, the thyristors from being broken. Furthermore, the joint portion X of the optical fibers can be kept airtight easily. |
