| The AC electric arc furnace (EAF) translates electric arc energy into heat energy in forms of arc, whose power is supplied by three phase AC provided by a special transformer. Aimed at the nonlinearity, multi-variable and strong couple of lead-zinc smelting AC EAF, A three-stage control mode adopting modern control theory and technology is introduced: proceed stage, control stage and drive stage. The control system is made of double closed loops: the inner current loop and the outer temperature loop, and satisfies the EAF's temperature need and three phase current balance . Temperature outer loop gives rational temperature and three phase current balance signals through EAF's practical actuality by fuzzy and expert control,, and combine the constraint of transformer characterstics and energy-saving ,thus provides optimal electrode's current instruction signal for three-phase current balance inner loop through expert optimizing decision. The inner loop for current balance control aims at fast tracking the instruction current and minimum of electrode's vibration, clarifies the error between instruction current and feedback current into different grades through intelligent means, and then realizes three-electrode current balance by means of expert fuzzy decouple intelligent control. This system assures three phase current balance and temperature stabilization.The system made up of high-quality periphery modules, based on industry control computer . Anti-disturbance measures of hardware and software are taken to assure the system's stability and security. The web-based system can realize long-distance control and management.It is proved that the system has a friendly interface which make it convenient to operate, meanwhile, It can achieve real-time adaptation to the changes of furnace conditions by practical running, enhance the quality of product and productivity, reduce electric energy and electrode consumptions. It has good social economic benefit and practical extend value.
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