Compact Modelling of Electric Arc Furnace Electrodes for Vibration Analysis, Detection and Suppression

Electrodes motion and positioning are critical issues of the Electric Arc Furnace (EAF) operation in steelmaking process. During the melting process electrode is exposed to some impulsive and harmonic forces, superimposing to the structure’s static loading. Unfortunately, structural vibration may interact with the electric arc regulation, because of the dynamic resonance. Instability in the furnace power supplying and dangerous electrode breakage may occur as a consequence of those dynamic effects. In this paper the dynamic behaviour of a real EAF structure is discussed and some numerical models are proposed. Available experimental data, collected by a monitoring system on a real operating plant, allowed detecting the relevant phenomena related to the electrodes’ vibration. Flexural and torsional modes were observed and so-called ‘common’ and ‘differential’ flexural modes were detected and distinguished, thanks to a deep numerical investigation. A full three-dimensional FEM analysis was performed to identify the global and local effects of vibration. Modelling activity was then aimed at shortening both the modelling and the computational times. Some approaches, based on different elements and mesh refinements, were then compared. Changes in the natural frequency of the structure due to the variable instantaneous position of the arm was tracked to suitably set a notch filter on the motion control. A further model order reduction was implemented to simplify the structural model. Experimental validation was preliminary performed on the existing plant and some confirmations on the effectiveness of the proposed models were found.

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