Analysis of characteristics of electric arc furnaces as control objects

Small-scale analysis of the operating modes of electric arc furnaces (EAFs) has been performed under conditions of basic control and disturbing effects. The influence of the nonlinearity of the current-carrying conductor on the power-transmission coefficients has been investigated for different melting-process stages. The study of the adjusting characteristics of the furnace has shown that power-transmission coefficients have a sign-alternating character during movements of electrodes with transition through zero at maximum power, which makes such a control action ineffective under the above conditions. The nonlinearity of the current-carrying conductor weakly affects the current value at the maximum power, but it reduces the arc voltage and length. The values of power-transmission coefficients comparable in arc length and current in the working range of the operating conditions show an equivalence of the controllers that stabilize the current or the arc length (arc voltage) in terms of the accuracy of controlling the arc power. It has been shown that the current-transmission coefficient during the melting stage reaches considerable values, which causes pronounced changes in the furnace conditions and occurrence of the flicker. It has been established that, to mitigate the adverse effect of the supply-voltage disturbance, it is reasonable to apply current controllers.