Regarding S7-PLC redundancy issues
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Dear colleagues, my company recently upgraded the PLC system in the main factory building to a redundant system; an ET200M was installed in each remote I/O station, and the number of CPUs was increased to two. After using this system for some time, we encountered frequent problems such as equipment failing to start or stop properly, as well as false alarms. Upon examining the program simulations, it turned out that certain components were set to a active state when they shouldn’t have been – there were errors in the program, even though no actual signals were present on the peripherals. I would appreciate any advice you can offer. Thank you.
It seems your description still isn’t clear enough. Is it set because of an external signal?
No signal is available from the outside. If the setting occurs due to an external signal, then that’s normal; but since there is no external signal, the PLC starts giving incorrect readings, producing erroneous outputs, and making unauthorized settings
What PLC is being used? Could you provide more details? It seems that the two systems aren’t synchronized properly
I’m not sure if a 300PLC is being used; if so, it’s necessary to determine which one is the master station and to check whether the programs for the two stations are identical. Monitor to see if there are any issues with the program
300 can only provide soft redundancy, which has no practical significance; the 400 system features hard redundancy, so the problem you mentioned hardly exists.
Yes, ours uses soft redundancy – we simply add an additional CPU and IM153 unit – but after implementation it starts to malfunction frequently and give false alarms. Please help analyze the reasons. Thank you
It’s most likely due to inconsistencies in the updates of redundant data; detailed configuration information and software programs from your end are needed to analyze the specific cause