Improving the quality of tension regulation in the strip of the continuous hot galvanizing unit

The paper studies a system of interconnected electric drives in the operational area of the continuous hot dip galvanizing unit located in the coating shop at PJSC Magnitogorsk Iron and Steel Works (PJSC MMK). It particularly focuses on the mechanical part with elastic elements and electric drive control systems. The paper aims at studying the existing operating modes of electric drives of the main mechanisms in the operational and output areas of the galvanizing unit; identifying ways to improve the static and dynamic performance of the interconnected electric drives system; developing an improved control system that provides for the better dynamic performance with indirect strip tension control. The authors propose a new control system for the operational area electric drives with corrective speed feedback. The dynamic characteristics of the traditional and the proposed systems were studied using a mathematical model of electric drives of the analyzed section with account to their interconnection via an elastic strip. The model accounts for eight electric drives, i.e., a hot tension station, tension stations no. 3, 4, 5, 6 and a training stand. Each electric drive is modeled with account for mechanical inertia and a (speed or torque) control system. The comparative analysis of tension control quality indicators for these systems proved the advantages of the developed system. The research outcomes can be used for similar units of continuous strip processing, featuring the technological line sections with a significant length of the strip between the adjacent electric drives.