傳統(tǒng)意義上，PLC主、備切換經(jīng)常采用繼電器方式，這種方式安全可靠，但是，備用PLC無法獲得主用PLC中的某些狀態(tài)量，如模擬量、掃查量等；如果主用PLC中的程序帶有順序標(biāo)志位，或者需要保持外圍設(shè)備的繼電器,一旦進(jìn)行主、備切換，程序?qū)o法繼續(xù)正常運(yùn)行、外圍設(shè)備將有可能停運(yùn)。本文針對GE Fanuc系列90-30 PLC利用網(wǎng)絡(luò)技術(shù)提出了一套解決方案，有效地解決了PLC主、備切換中容易產(chǎn)生的問題，并應(yīng)用于實(shí)際工程中，獲得了不錯的效果。

主、備切換；網(wǎng)絡(luò)技術(shù)；繼電器
Abstract: Traditionally, the switch of PLC between master and slave always uses relay, it is reliable and secure, however, slave PLC can not acquire status variables with this method, such as analogue values, digital input status, and so on; if there were some sequence flags or must keep relays of peripheral equipment, program can not run as usual, and peripheral equipment may be stopped when the switch completed. This paper provides a set of method, which is used in GE Fanuc Series 90-30 PLC with network technology; it can solve problems produced by the switch, and acquires good result in real project.
Keyword: switch between master and slave; network technology; relay

1、前言 2、傳統(tǒng)主、備切換方式的原理及弊端 3、新方法原理 4、傳統(tǒng)方法與新方法的比較 5、實(shí)際項(xiàng)目應(yīng)用 6、結(jié)論 7、參考文獻(xiàn) 詳細(xì)情況，請下載本手冊