| 摘要 |
PURPOSE:To reliably protect by providing a protecting circuit in which the protecting level of an overvoltage approaches a normal time voltage, thereby shortening the protecting operation delay time. CONSTITUTION:The voltage of a capacitor 19 becomes equal to the voltage of a main thyristor except when the voltage of a main thyristor 10 becomes lower than the voltage of the capacitor. Accordingly, a natural breakover element 21 can be turned ON without delay time to the excess voltage. The capacitor 19 also becomes a supply power source of a gate pulse of the thyristor 10. Then, the gate voltage of the thyristor 10 is limited to the prescribed voltage or lower by a Zener diode 22, the current is limited by a resistor 20 and a gate pulse shaper 17 to generate the optimum gate pulse, thereby reliably turning ON the thyristor 10 and bypassing the excess energy. |
