Web handling sometimes requires two or more motors to control one section of a machine. Speed and torque must be balanced or controlled between these drives.
- A center driven unwind may be able to provide more tension without core slip if both ends of the core are driven.
- Calenders often have 2 or more rollers which must operate nipped or unnipped.
- Coaters may involve nipped rollers with 2 motors.
- Center/Surface winders need 2 or more motors with sophisticated load sharing (torque split) based on winding roll diameter.
- Paper Machine forming sections and press sections often require several driven rollers in order to provide enough total torque to the section.
Modern system drives incorporated load sharing schemes to coordinate speed and control torque to each motor. This may require peer to peer communications between the drives with dedicated copper or fiber optic cables.
The drives may operate as independent speed regulators when the motors are mechanically independent. When the drives are mechanically tied together by nip web or fabric, one drive is selected as the speed master. Other drives are configured as followers of the master drive. If torque control is very sensitive, the master drive's speed regulator controls all the motors in that section.