| 摘要 |
PURPOSE:To reliably turn OFF a thyristor without damage by providing a gamma- limiter which produces a pulse at the prescribed maximum delay phase angle and a pulse lock circuit for interrupting the normal firing control pulse. CONSTITUTION:A firing control pulse controlled in phase by a phase control unit 21 is inputted to gamma-limiter 22 corresponding to the necessary reactor current to compensate the generated reactive power in a reactive power control unit 20 of a controller 19. This limiter 22 always outputs a pulse at the maximum delay phase angle predetermined even when the firing control pulse phase control signal is maximum throttle command. A pulse lock circuit 23 operates corresponding to the forcible firing signal, and interrupts the firing control pulse transmitted to the thyristor of reverse phase to the thyristor, to which the forward overvoltage is applied at least by one cycle. |
