I am facing issue in dc drive 590+ dc integrator. My application is on coating machine where a roll is rotated through drive and it runs with constant speed in standalone condition. But as per process need the roll is closing nip with another roll which is just above it (means both rolls are in common vertical plane) the speed variation starts. I decoupled motor and checked tacho generator, motor condition. It was fine. I also performed autotuning and I expect that P,I values in speed loop are also correct. Another observation is that the load of the motor after nip closing is raising more than past condition when it was all normal.
Am I missing something ?