I have to to keep at the maximum effciency the running of a 250 HP mill motor that grinds animal pellets. This pellets are fed by a rotary valve that has a 1.5 HP motor controlled by the referred drive. I have a a KW transducer , EMOTRON M20 , which senses the power demanded by the 250 HP motor and its analog inverter output 20 - 4 mA is fed to the analog input of the drive in such way that when the load is low the VFD should speed up the rotary valve ( feeder ) in order to increase the load on the mill motor. this should be done automatic through the PI controller on the drive. My question is which values should I place in the PI controller at the beginning and how do I know that I have reached the optimal values ?. please think that I do not have any experience at all with PI controllers.
I would be very grateful for any help .

comapro

There is no EASY answer to your question.

P-I Controllers are the heart of a Closed Loop system (one that uses feedback eminating from the controlled variable).

Engineering students study Closed Loop Control systems in their 3rd or 4th year of studies at the University.

With no experience and undoubtedly no knowlege of the theory of Closed Loop Control systems, it is beyond the scope of this forum to impart to you the knowledge necessary to successfully 'tune' a Closed Loop P-I system. (Additionally, there is much application information that you haven't shared with us, the ommission of which gives the readers an extremely limited view and understanding of your particular system.)

Recommendation:

1. Contact the Tech Support people at the manufacturer of your system (the people that designed and built it)
for the assistance that you need.

2. You might also want to talk the the Tech. Support group at G.E., the manufacturer of your VFD, about how to adjust the P-I parameters of the drive you have

Doing so will save you a lot of screwing around time ....