| 摘要 |
PURPOSE:To replace a burned-out lamp safely without putting out other lamps by detecting overvoltage upon blowout of a lamp at the secondary of a CT then repeating short circuit/opening at the secondary of the CT and continuing short circuit upon elapse of predetermined time. CONSTITUTION:Upon burnout of a lamp L1 at the secondary of a CT1, overvoltage produced at the secondary of the CT1 is detected and a contact 14a is turned ON by means of a relay shown on the drawing. Consequently, a relay 19 is energized and self held at the contact 19a, and timers T1, T3 (T1<T3) are started through the contacts 19b, 19c. Contact 15a is turned ON to start a timer T2 upon elapse of time T1, and a contact 16a is turned ON to fire a thyristor 10 through a thyristor firing circuit 13 so as to short-circuit the CT1. The contact 16b is turned OFF to de-energize the timer T1 upon elapse of time T2 so as to turn the contacts 15a, 16a OFF. The thyristor 10 is also turned OFF to open the secondary of the CT1. Opening/short circuit are repeated, and the contact 18a is turned ON, upon elapse of time T3, to keep firing of the thyristor 10 so as to shirt-circuit a CT2 continuously. By such arrangement, only a burned-out lamp can be replaced without putting out other lamps. |
