PI Loop with a CLICK PLC

[VFDtech]

Working on a program using the Koyo CLICK PLC...

Need to develop a PI loop to maintain water pressure on a booster pump system with a 0-200 PSI (4-20) feedback signal. This includes 3 individual pumps that also will have Lead/Lag switchable inputs between all three pumps (ABC, BCA,CAB) scenario with will rotate at some given time (ex. every 48 hours). The pumps will be driven by VFDs. Initially I need a decent PI loop with a fairly aggressive Gain and short I-time. Ex. Gain = 10.0 , I-time = 3 Secs. The twist is if any one of the VFDs should experience a fault or loss of power (a digital input will be provided from each drive), then the next pump drive needs to be activated in its place. The lead pump will control by the PI loop; the Lag pump(s) will be controlled by the lead pump by an Analog output off the Lead. Again back to the twist, in the event of a lag or even lead pump vfd failure, it needs to switch not only the digital start command, but also the analog output to the follower (lag).

This is an example of a PID program someone designed.

http://openbookproject.net/books/soc...oc/design.html

Scroll second to the bottom thread entitled

"PID control programs for Automation Direct "CLICK" PLC"

Just wanted to confirm the layout. It might be useable.


Here is another example of a PID loop designed with a CLICK PLC

http://www.youtube.com/watch?v=f8J1_ClCf6k

 

[xJAyx]

This sounds like 2 different problems to me. The pump failure and the pressure control can be handled separately.

As for the PI loop, are you stuck with the Click PLC? There are plenty of low cost PLCs with built in PID functions. The link is broken, si I can't say wether that would work or not.

For the lag pumps, how are they "controlled by the lead pump by an Analog output off the Lead"? To me I would suggest that you just run all of the analog signals to the VFDs from your PLC and it will be easier to rotatate which is the lead and which are the lag pumps.