DEVELOPMENT AND ANALYSIS OF THE ELECTRIC ARC MODEL IN ELECTRIC-ARC FURNACE WITH OPTIMIZATION OF ELECTRODES MOVEMENT

V elektroobločni peči je primarni vir energije toplota, ki nastane pri gorenju obloka med elektrodami in jeklenim odpadkom v obločni peči. Pri električnem obloku gre za električno razelektritev skozi pline med dvema elektrodama (anodo in katodo), ki ju napaja izvor napetosti. V elektro-obločni peči gori med vložkom in grafitno elektrodo električni oblok, za katerega je značilen stolpec plazme visoke temperature (prisotnost negativnih nosilcev naboja – elektronov in ionov, ter pozitivnih nosilcev naboja – ionov). Za samo delovanje obločne peči je daleč najpomembnejši fizikalni pojav prevodnega stolpca obloka med elektrodama. Plazma v stolpcu obloka pri atmosferskem tlaku in velikem toku je vedno v termodinamičnem ravnovesju. Visok tlak in visoke temperature na elektrodah povzročijo močan prenos toplotne energije in s tem taljenje in izparevanje elektrodnega materiala. Večina avtorjev je obravnavala obločno peč kot električno nadomestno vezje, kjer je bil oblok modeliran kot linearni upor, napetost na obloku je bila modelirana s pravokotnim signalom napetosti, uporabili so Cassie - jev model obloka ali model napetosti na obloku, zapisana s sistemom višjih harmonskih komponent. Vsem tem modelom je skupno, da so analitične enačbe rešljive v stacionarnih razmerah za osnovni harmonik napetosti in toka. V doktorski disertaciji je predstavljen ustrezen fizikalni model obloka, ki opisuje fizikalne lastnosti obloka v obločni peči in kot rezultat poda napetost, potrebno za gorenje obloka pri različnih tokovih, ki tečejo skozi oblok. V kolikor se model obloka implementira tudi v nadomestno vezje obločne peči, se lahko določi delež vnosa toplotne energije pod posamezno elektrodo. Na podlagi vnosa toplotne energije pod posamezno elektrodo se lahko določi možnost nastanka vročega ali hladnega področja v okolici elektrode, pod katero vnos energije odstopa od ostalih dveh elektrod. Zaznava in odprava neenakomernega vnosa toplotne energije v obločno peč, s pomočjo bolj optimalnega delovanja regulatorja gibanja elektrod, ima velik doprinos k znižanju obratovalnih stroškov obločne peči.For electric-arc furnace is the primary source of heat energy generated by the burning arc between the graphite electrodes and steel scrap. Electric arc is formed when electric discharge occurs through a gas between two electrodes (anode and cathode), which is powered by a voltage source. In electric arc furnace between the scrap and graphite electrode electric arc is burning, and is characterized by high temperature plasma column (with presence of negative charge carriers - electrons and positive charge carriers - ions). For the electric arc furnace operation is the most important physical phenomenon appearance of conductive arc column between electrodes. The plasma in the arc column at atmospheric pressure is always in the thermodynamic equilibrium. High pressure and high temperature cause high thermal load to electrodes and consequently melting of scrap and its evaporation. Most of the authors modeled the arc furnace as an electrical equivalent circuit, where the electric arc is modeled as a resistor, the arc voltage has been modeled with rectangular voltages signal, or they used Cassie\u27s or Mayr\u27s model of the arc or they wrote electric arc voltage as a system of higher harmonic components. All these models have in common that analytical equations can be solved in a steady state for a first harmonic of voltage and current. In this dissertation the physical model of the electric arc in arc furnace is presented. Physical model of the electric arc describes properties of the arc in an arc furnace, which as a result returns the arc voltage needed for the burning of electric arc at different currents flowing through the arc column. If physical model of the electric arc is implemented in the arc furnace equivalent circuit then input of thermal energy under a single electrode can be determined. Based on the input of thermal energy at all electrodes the possibility of occurrence of hot or cold spots can be determined. Perception and the elimination of the un equal heat load under electrodes has a major contribution to reducing the operating costs and increase the effectivity of electric arc furnace production