Compensation of a digitally controlled static power converter for the damping of rolling mill torsional vibration

A significant advance in damping of torsional vibration by the application of an additional control loop is described. The control feeds measured spindle torque into the drive current regulator, typically increasing damping by 50 to 100%, which is comparable with other damping methods reviewed. A scale model and a large full-scale mill have both been tested with the new control loop. The increased damping is required as a result of efforts to increase rolling mill production through higher speeds and bite angles, with a consequent increase in the incidence of resonant torsional vibration problems such as shudder or chatter. A large reduction in motor speed drop and recovery time is an additional benefit. Tuning of the motor speed and current regulators can be of some help in improving the damping of the drive system; however, the speed-sensor ripple and sampling delays of the digital speed regulator limit the scope for improvement