3BSE003644R1 ABB

Most of the faults in the PLC control system are checked out by the PLC program.Some faults can directly display the cause of the alarm on the screen;some have alarm information on the screen,but do not directly reflect the cause of the alarm;some faults do not generate alarm information,but some actions are not executed.In the latter two cases,tracking the operation of the PLC program is an effective method for diagnosing the fault.For simple faults,information can be displayed according to the status of the program through the PLC,monitoring the status of related inputs,outputs and flags,and tracking the operation of the program,while for complex faults,a programmer must be used to track the operation of the program.If a water pump does not work,check and find that the corresponding PLC output port is 0,so by checking the program,it is found that the hot water pump is still controlled by the water temperature.If the water temperature is not enough,the PLC has no output.

PLC控制系统出现的绝大部分故障都是通过PLC程序检查出来的。有些故障可在屏幕上直接显示出报警原因;有些虽然在屏幕上有报警信息，但并没有直接反映出报警的原因;还有些故障不产生报警信息，只是有些动作不执行。遇到后两种情况，跟踪PLC程序的运行是确诊故障的有效方法。对于简单故障可根据程序通过PLC的状态显示信息，监视相关输人、输出及标志位的状态，跟踪程序的运行，而复杂的故障必须使用编程器来跟踪程序的运行。如某水泵不工作，检查发现对应的PLC输出端口为0，于是通过查看程序发现热水泵还受到水温的控制，水温不够PLC就没有输出，把水温升高后故障排除。