| 摘要 |
PURPOSE:To suppress the stationary loss of a semiconductor element without spoiling arcless breaking and high-speed breaking performance by connecting a vacuum bulb, which is turned on normally and turned off in the case of flowing an overcurrent in parallel. CONSTITUTION:A gate turning-off thyristor 1 has a 1-2V forward voltage drop, so a current flows through the vacuum bulb 5 with small resistance. If a DC short circuit accident occurs on an output side at time t1, the current flows through the vacuum bulb 5 and the current value detected by a current transformer 3a is increased and if the current value exceeds a breaking set value I0 at time t2, a control part 6 opens the vacuum bulb 5. Then the current flowing to the bulb 5 is diverted to the side of the thyristor 1 from time t3 to be decreased. Consequently, the current flows through the thyristor 1. When a current transformer 3b detects the current flowing through the bulb 5 being ceased, the control part 6 sends a signal to the thyristor 1 to break the accident current and an absorber 2 suppresses a developed voltage. |
