GV3000 questions

[Emach 0]

A few quick questions on the GV3000. I have a 20HP, 460V unit that is currently driving me crazy. It has an encoder installed and still (in the opinion of my product engineers) has an unacceptable level of instability. This drive is very lightly loaded and I have backed the speed and torque PI values back to default values but I can't quite seem to get the drive to run perfectly smooth. Is anyone a GV3000 guru or can someone point me to a resource beyond the software manual? Addendum, my senior plant EE insists that even with an encoder connected, reported speed is based on flux not on the encoder... I find that hard to believe. The manual stays silent on how it calculates speed in FVC. Plot of the speed going from 500 to 7000 RPM. I see a +/- 10RPM ripple once I start doing 1000 RPM jumps above 2000 RPM. Ok round 3, let me refine my question a bit more. Can someone provide the torque controller block diagram? It is only shown as a black box in the software reference guide. Knowing how and where the flux current regulator comes into play in the torque controller would be handy. Thanks, Emach Edited 20 Jan 2012 by Emach