AC800F Export Variables no update
We have a Freelance system (version 2013) with AC800F controllers and in two opportunities we have experimented a issue with the exchange variable between controllers. the variables that are sent, exported, to other controller are not update. The issue has been solved after to do a re-init (Power off- Power on) the controllers and do a "whole station". But I need a explain why it happen. The issue happen with analog and digital variables. In one case only a toggle of the controller was enough to solve the issue for the digital variables, but it didn't for analog ones. I think that the issue begin with a power fail in the controllers, but it doesn't explain why the variable communication between controller is not working properly.
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Of coarse I made support requests to ABB, but the results were not really satisfying.
At the first time the ABB support suspected the "load selected" function to be the root issue (that's why they removed this in 2013). They suggested "load whole station" to solve this issue, what I had already done.
The second time they suggested to just remove the buffer batteries and power cycle the faulty controller, but this failed due an unrelated reason. "Load while station" again...
I guess the secondary controller got it's latcom receive function corrupted somehow in the past, but no one note because it's the secondary and all is working fine.
Then we had a redundancy toggle and the error appears. If we do toggle back all is fine. If we toggle again the error appears again.
I would suggest you to write a support request to ABB. Maybe your case does lead them to find the real root of this dangerous issue.
Answers
There is a Technical Bulletin 3BDD011838D0251 with the title "Freelance: Stop of Lateral Communication after cold start or redundancy fail over"
It describes your situation. Though it claims that the problem does not exist with versions higher than V8.1 it gives some good advice how the problem can be avoided and also names a Tool that can determine, whether your system has that hidden issue or not. I'm not sure that the tool works with newer Freelance versions. Let me check with R&D.
Which version are you running? Freelance 2013, 2013SP1 or Freelance 2016?
The Technical bulletin and the Tool are available in MyControlSystem, provided you have a valid Sentinel agreement. Let me know if you can download the bulletin.
3BDD011838D02513BDD011838D02513BDD011838D0251
Here is the support feedback:
I my case, I think that the issue arises because the customer changed the task cycle time in one of the tasks, what could increase the Red Link Load to 100%.
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Regarding the LATCOM issue
Generally:
Firstly, I would like to confirm that “Load whole station” was the correct action – to load completely both controllers if LATCOM issues are observed.
(Load whole station mean short production stop, and starting with initial values.)
It is NOT needed to Power off-on the controllers before “load whole station “.
As the load whole stations was done, currently I cannot further analyze the issue, as the controller were newly loaded, and lost some important information from logs for further analysis (in the time of latcom problems).
One of the reasons for the latcom issues is/was that some changes were not loaded properly to some of the controller.
(This is seen also in PB - 3BDD011838D0301_A function “load selected objects“ was in past causing similar inconsistency which led to Latcom problems.)
For better identification of Latcom issue can be: put Latcom variables (PSx.Psy.RcvErr, PSx.Psy.SendErr) to call alarm/message
If latcom issue is again observed - we recommend:
To save the controller diagnostic logs from affected controllers
1. In the Freelance Engineering please perform the “Check all” procedure of the complete project tree.
If some loading “arrow” will appear by some controller, please load “changes“ to that controller(s).
2. If “load changes” not helpful to the latcom -then “load whole station(s)“
In the past we had some cases with Latcom, since version F2016 we have no Latcom cases reported, also with this version latcom improvements were done. (PRC23788)
Additionally:
In this case I have found controller diagnostic logs – I can see that A251 controller has 100% Red link load, and this is the potential cause of the Latcom issue. Recommended limit is to keep Red link load under 80%. If 100% - unexpected behavior can occur.
RedLink Load is a sum of:
1. Task cycle time
2. Objects
3. Process variables
4. CPU load
How to reduce Red link load
· increase TASK cycle time
· or decrease the amount of transported variables (Variables with Export attribute, or process image)
· or/and use non-redundant TASK instead of redundant TASK in the redundant station (if acceptable, because after redundancy toggle variables starts with initial values)
· or/and distribute part of the configuration to another controller.
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Regards,
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