| 摘要 |
PURPOSE:To shorten a waiting time up to the reclosing of a power source by connecting a level shifting Zener diode through a diode directly with an AC power source and commutating a thyristor conducted at the abnormal time therewith. CONSTITUTION:The resetter of a protecting circuit rectifies an AC power source 7 via diodes 16 and level-shifts it via a Zener diode 17. An electrolytic condenser 19 is charged by the current flowed through the diode 17, the voltage is divided by resistors 20, 21, and applied to a transistor (Tr)22. When a malfunction occurs in a control circuit 2 in this state to cause a thyristor 3 to be conducted, an electrolytic condenser 23 is discharged, and when an AC switch 5 is opened OFF due to the recovery, the condenser 23 is discharged to turn OFF the Tr22. Thus, when the switch 5 is reclosed, the Tr22 is immediately turned ON to cause the thyristor 3 to be reversely biased. Accordingly, the thyristor 3 is turned OFF to start the control circuit 2. |
