Integral Limit Reached

Keith P

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K
Join Date
May 2011
Location
Summerville, Oregon
Posts
2
I have a PLC 5 with loop controls for positioning Pins and saws in a lumber mill. Recently it has started having the Error Integral limit reached. This has not caused any failures but I would still like to know the cause of this error since I'm not real familiar with PLC 5. ☯
 
Maybe I didn't say this right.

:confused:This error is in a QB loop drive controller right out of the book integral limit reached. It turns off when integral term returns within the permitted limits. I still haven't found the limits through the book. Sorry you thought it was miss stated which it probably was but I'm still seeking the parameters and control word. THX
 
See exert from the manual. What do you have the max set for?

And a link to the manual if you don't have it.

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1771-um654_-en-p.pdf

Bit 8 – Integral Limit Reached
The integral limit reached bit turns on if the integral term of the PID algorithm
reaches the maximum specified in the parameter block. (See Chapter 7.) It turns
off when the integral term returns to within the permitted limits. Reaching the
integral limit doesn’t result in a loop fault

Integral Term Limit (words 16 and 45)
The integral term limit parameter determines the maximum value that the
integral term of the PID algorithm can obtain. You use this parameter for alarms
and/or limiting.
The integral term limit prevents the integral term from causing maximum
analog output if there is an undetected analog or hydraulic fault (e.g., if the
hydraulic pump is off).
Click to expand...
 
Last edited:
I dont know the PID block in PLC5, but it sounds to me as a safety measure to counter integrator wind-up. That this message bit starts to trigger can indicate that something has changed.
Integrator wind-up can happen if the controlling parameter has reached maximum, or there is a hardware error as described by Mickey's link.
Another cause is if there is an error in the feedback signal, for example the signal is plausible but the error means that the PID can never settle on the target value.

So I suggest you would check your controlling device(s) and your feedback signal(s).
 

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