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Moorthy

Jazz: Pid with cascading function

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Dear Gentlemen,

 

I'm rather new to Unitronics. Worked with Vision 230 couple of months on some simple control system. Now am working with Jazz-10-UA24Z.

Making  constant pressure boosting pump set control system. 2 pumps in parallel configuration which run on vfds, Feedback from a pressure transducer on the discharge manifold as PV, input. Analogue out from plc to vfds as speed reference, paralleled. I've got the pid part sorted out. Can anyone assist on

1. How to incorporate the cascading function to the program?

 

Thanks,

Moorthy.

 

 

  

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if by cascading you mean lead/lag function then there are several ways to do this but one way is:

 

you tell the system to hold a particular pressure.  Run pump 1 only ........ if pump 1 has to run greater than 90% of capacity for more than a programed amount of time then bring pump 2 on line to help pump 1.  If the combination of pump 1 and 2 runs for less than say 40% of capacity for a programmed amount of time then turn pump 2 off and let lead pump (pump 1) handle all of the load.

 

Automatically switch which pump is the lead pump when both pumps stop to equalize run time.  Or automatically switch after a certian amount of time.  If switching on the fly, then make sure that lag pump is brought up to speed before shutting down lead pump to smooth out switchover transition.

 

Thanks

Keith

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Hi Guru,

 

Thanks for the reply. You've the cascading part right. Perfect.

 

What I meant is if there are any function blocks in U90 that could represent cascading one way or another? Since I'm new to U90 haven't got a chance to fully explore it.

 

Thanks again,

Moorthy

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I am unaware of any pre-built function blocks that will do the cascading you want.  You have to write it out long hand in the nets with timers and compare blocks to make the lead lag control you want.

 

Good Luck

Keith

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