Control System for Electric Drives of Plate Straightening Machines

The essential quality parameter of rolled products is the flatness along the rolled stock length. The profile defects of the rolled stock, produced at the modern plate mill 5000, frequently occur in the course of intense cooling implied by the thermomechanical rolling technology. To eliminate them, the mill lines include cold straightening machines. The authors show typical flatness defects caused by the occurrence of longitudinal, central and edge waves. Further, the paper characterizes a cold straightening machine installed at the mill 5000 and provides the parameters of electric engines of straightening rollers. The key drawback of the design algorithm for electric drives’ control is setting engine constant moments regardless of the thickness and character of the defects in the rolled stock processed. This causes overloading of the electric and mechanical systems of certain rollers and unsatisfactory product quality. To eliminate the drawback, the authors developed a method for individual setting of engine moments closely coupled in the course of sheet processing. The authors present a functional block diagram for the control system to implement the method. The rationale is provided for the digital setting of moment controllers switched on the inputs of speed controllers. The authors conducted simulation modelling and comparative analysis of engine speeds and moments at the design and proposed settings. The paper provides the analysis of oscillograms obtained before and after the introduction of the control system developed. Its technical and economic feasibility was confirmed during operation.