Asymmetrical Power Control of AC-EAFs by Structure-Borne Sound Evaluation

摘要

It is shown that the state of the meltdown process can be estimated by several evaluation methods. Especially the occurrence of panels not being shielded by scrap can be detected through structure-borne sound evaluation. Taking into account other signals like the thermal load of the cooling panels and the signal for detecting cold scrap at the arc base, a new feedback power control can be set up. Aiming at an efficient and fast meltdown operation, asymmetrical distribution of radiant power is favorable. A feasibility investigation of known radiation models regarding the impedance setpoints shows that only some models yield reasonable results. After selecting one of these models, it was shown how the impedance setpoints can be adapted to the observed state of the meltdown process. In the presented way, the radiant power of the three phases can be redistributed in accordance with the meltdown progress. Avoiding excessive thermal loads and symmetrically melting down the scrap, a higher productivity as well as reduced furnace wear can be achieved. Additionally, the transformer tap and the primary reactor can also be controlled based on the newly developed evaluation methods. The approaches presented in this paper will be used in a new commercial product called 'SIMELT Condition-based Scrap Monitoring' by Siemens AG.