| 摘要 |
PURPOSE:To attain an alarm output at power-down, to reduce the cost and to improve the reliability by providing a relay having a closed contact when no power interruption or no output instruction exists at an output section so as to eliminate the need for an accessory circuit. CONSTITUTION:In closing a contact 1 with a target with the operation of a protective relay 1 and giving a signal of a contact 1 to an input section 3 of a programmable controller (PC) 2, the PC 2 reads this signal via a port connected with the contact 1 and applies a prescribed processing attended with an input signal according to a program. An exciting circuit of an auxiliary relay 5 is connected to a specific port of an output section 4 and the contact 1 is connected to a DC line N via a contact 5b of a relay 5, then the contact 1 is closed and a target current flows through the contact 5b and a target current adjusting resistor 7 to operate the target of the contact 1. On the other hand, the input signal to the PC 2 is processed by a program and the PC 2 activates the relay 5 according to the program. Then the contact 5b is opened to cut off the target current of the contact 1.
|
