COMPARISON OF DIRECT-CURRENT AND 3-PHASE AC ARC FURNACES

The power of the three-phase a.c. furnace is limited in Germany according of the VDE standards to about 96 MW, which makes it possible to achieve a yearly production of 1.2 million t at a tap weight of 160 t. The power of the direct-current furnace is limited to similar levels by the voltage and length of the electric arc and by the current-carrying capacity of the graphite electrode. At a realistic assessment of the graphite consumption, clearly lower processing costs of the direct-current furnace can be achieved only through energy saving. The main advantages of the direct-current furnace are the more uniform melting of the charge and the smaller voltage fluctuations in the supply system. If the latter advantage is irrelevant because of a powerful supply system, the higher investment costs of the direct-current furnace represent, similarly to the bottom electrode, a disadvantage.