Speed Coordination System for Electric Drives of a Plate Mill Stand: Theory and Development

This paper briefly analyzes the technology behind the upward bending of the frontend of the strip leaving the reversing stand of a plate mill. It emphasizes the importance of more precise speed coordination of motors driving the horizontal rolls. The paper further presents the results of testing a variety of speed and load parameters. It concludes that the upper roll and the lower roll differ significantly in motor torque. This difference is attributable to the significant dynamic deviations in speed that are observed when the rolls nip the metal strip, and to the fact that the load distribution controller (LDC) is slow. The paper showcases the author-developed method for motor speed coordination during frontend bending. It proposes a control system featuring a switching structure. The paper further shows the structure of a model that simulates connected roll drives. Simulations prove more precise speed control during frontend bending. This finding has been confirmed by experimentation. The method has been implemented as an algorithm on Mill 5000. The paper concludes with recommendations on its adoption in plate mills.