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

The power of the three-phase a.c. furnace is limited in Germany accord ing of the VDE standards to about 96 MW, which makes it possible to ac hieve a yearly production of 1.2 million t at a tap weight of 160 t. T he power of the direct-current furnace is limited to similar levels by the voltage and length of the electric arc and by the current-carryin g capacity of the graphite electrode. At a realistic assessment of the graphite consumption, clearly lower processing costs of the direct-cu rrent furnace can be achieved only through energy saving. The main adv antages 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 sys tem, the higher investment costs of the direct-current furnace represe nt, similarly to the bottom electrode, a disadvantage.