DCS800 Speed fluctuation at Field Weakening
Hi, I am working in a paper Mill. I am having strange issue on DCS 800 drive. I am getting erratic encoder feedback at certain speed with load and even using with the speed error filter and filter time, still motor actual speed fluctuates 4-6 rpm whereas Encoder speed varies from 40-50 rpm at 1700rpm motor speed. Is there any other way I can filter the encoder feedback. I am using earthing at one end of the encoder cable. Changed the motor, encoder & cable and issue still remains the same. Did the speed tuning and adjust KP & Ti and did the field weakening tune. Motor speed looks good up to base speed- variation starts more at field weakening region. I checked motor speed at no load and looked good.
Motor application: Forward Drive running as Master with Couch As Follower.
Motor: Siemens 302KW, 800A, 1480 base speed, field current 12.5
Any suggestion would be appreciated.
I suggest to check circumference speed of each roll which is in mechanical contact with Master drive by felt etc.
The best way is measuring with speed meter attached directly at roll circumference with no paper at machine. Circumference speed must match at all rolls if draw is set zero.
The aim of measurement is to align speed of all drives at no load and to avoid oscillation between drives in mechanical contact.