I have AC800M PM864 Controller-> CI854 (Redundant Configuration) and 12nodes of CI840.
I have Problems in my CEX bus(As per Controller Log..-For this Problem, we have already sought our Regional ABB Support and they are expected to attend problem shortly).
Due to this problems in CEX bus, frequent switchover happens between Primary and secondary CI854 and at this time entire plant operations go off and things become normal after 2 minutes. So as of now, we would like to know the alternatives.
My doubts are:
1) Among the 12 nodes (CI840), only 2 nodes are critical for Plant operations. I would like to take these nodes through Module Bus (using Cluster Module). Is this the correct alternative? is Module bus more reliable than CEX bus?
2) The Node which i would like to communicate through Module bus is approx. 50metres from controller. So if i lay an Optical fiber cable(single Mode) from controller to Cluster module, will the communication work?
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I would suggest you also wait for the answer from ABB as the behaviour you have is not normal and should not really happen. The CEX bus should be as reliable as the modulebus. According to your questions I can answer the following.
1) The idea of having the critical IO nodes on the modulebus cluster will with no doubt make your system more robust from this CEX bus issue you are having. Of course to do so you would have to consider other cluster modems (TB840) and also change the hw architecture in control builder, but as idea I find it interesting. What you have to know if you use modulebus this will use a portion of the controller to do the communications, and how much load it will have in the controller depends on the cycle time, task times, etc.
modulebus is propietary protocol and is directly handled by the controller.
2) If using modulebus and no special FO repeater (TB825) then you would need a special fiber optic to be used (HSC a expensive type of fiber), if you wish to use the single-node fiber then only with this special repeater interface it would work. Both hw connections would work.
Your other option is to simply remove the Redundant CPU's and configure the AC800M without redundancy. This may help you troubleshoot where the CEX bus problems are coming from.
You may find a big jump in CPU load if you move all of this IO from profibus to Modulebus, so monitor the CPU load.
No, the CEX bus should be reliable. On earlier versions of AC800M reduncdancy there did seem to be excessive problems with switching over and we found it better to run non-redundant CPU's. However, I have not used a redundant AC800M CPU for several years and I believe these problems should have been resolved.