I was asked to look at the tuning parameters for a generator oil cooler control loop for a GE Frame 7. It is being controlled by an ISA_PID MK-VI block. I searched for help files on the internet without success.

The plant is in another state and I haven't worked on a MK-VI for nearly 20 years.

Specifically I need to know how the proportional gain is scaled. The PG pin of the block is set for 5.4%/%. I'm thinking that for every % error there is a 5.4% output response. i.e. a gain of 5.4. That seems really high, but the trends I've seen look like the response is way too fast.

There is a pin labeled DA. It is currently set for 10. Any idea what that might be? The DG pin, I'm assuming is derivative gain, is set for 0. Would the derivative gain units be seconds or minutes?

Thanks so much,
Mully

 

Mully,

The best place to look for information about a block used in Mark VI application code would be to right-click on the block in Toolbox and then click on 'Block Help.' That would pull up a Help file for the block which will describe all of the inputs and outputs and the function of the block. [NOTE: GE is now using a LOT of macros, which is great for them, but there is no 'Block Help' for the macros.]

The only other thing I can add is that if I'm not mistaken there are two methods to implementing integrals--one is straight-forward, and the other is an inverse something-or-other. GE has historically used the inverse something-or-other method, which can make tuning difficult if one doesn't know that little tidbit of information.

I don't have access to Toolbox at this writing, or I'd try to find out something about the block and post it here; sorry. Maybe you could ask the tech's at the other site to right-click on the block and pull up the 'Block Help' and either do a screen copy/copies and send them to you, or print it to a .pdf file and send it to you--or take photos with their Smartphone and send them to you.

 

Sorry - I don't have access to a Mk VI either or its PID function, but I would like to have an image of the ISA_PID symbol could you cut a paste one from any docs to [email protected]. I'm writing SAMA logic for a Mk VI and need to make the PID acceptable to the end users. This would help me. The GE9030s use DG in seconds*100, the proportional gain is x100.