PLC故障分析一例

An Example of PLC Fault Analysis

对西门子S5 - 115U型PLC出现的一例隐性故障进行了详细分析和探讨。故障现象 1:PLC的CPU启动慢 ,且运行后无法通过网络传输数据 ;故障现象 2 :PLC中的 1块I/O模板上有 2个输出点在PLC启动后就置位 ,不受逻辑控制。经分析 ,发现故障I/O模板使PLC启动缓慢 ,也影响了PLC在运行过程中的总线通讯 ,使PLC的I/O寻址发生错误 ,更换故障模板后一切恢复正常。并由此得出如下有关S5 - 115U型PLC的经验 :故障诊断功能不完善 ;当I/O模板出现问题时 ,有可能对CPU的启动产生影响 ,也有可能使CP1430的启动出错 ,而且不一定是显示问题的I/O模板出了故障 ;CP1430的通讯组态程序可以存储在FLASH -RAM卡中 ,也可以存储在CP1430自带的RAM中等 。

An example of covered fault of Siemens S5-115U PLC was analyzed and discussed in detail. The symptom 1, CPU of PLC started up slowly and data could not be transferred by network after running. The symptom 2, two output points in an I/O module of PLC were set immediately after starting up, and failed to be controlled logically. It was found that the PLC starting up slowly was caused by fault I/O module, which influenced the bus communication as well, while PLC was running, and led to wrong address. PLC could back to normal once the fault module was replaced. Some experiences about S5-115U PLC were obtained: the function of fault diagnosing was unperfect. An fault I/O module would influence the starting up of PLC, and might misfuction the starting up of CP1430, and it was not necessarily the I/O module where the symptoms emerged had problems. The communication configuration program of CP1430 could be stored in FLASH-RAM, or in RAM of CP1430, among others. Those experiences were good for maintenance.