Direct-arc electric furnace fed with controlled current and method to feed a direct-arc furnace with controlled current

摘要

Method to feed a three-phase direct-arc electric furnace with controlled current and also a three-phase electric furnace thus fed for the smelting of metals, e.g. iron-based alloys, the furnace comprising means (GI) for regulation of the length of the arc by means of action on the height of the electrodes, the mains supply of the furnace including at least one medium voltage line and a transformer to serve the arc furnace, an element to regulate the arc current being comprised in each phase in the segment connecting the medium voltage line and the transformer and consisting of at least one inductor (L1), a thyristor- controlled valve (T) or alternatively a regulation element consisting of a saturable reactor being included in parallel with at least part of the inductor, one or the other of these regulation elements cooperating with a device (s1) to measure the intensity of the arc current and with an assembly (GC) that controls the arc current of the furnace by means of action on the overall value of the equivalent series reactance. The method includes feeding current to the furnace through the mains supply and varying the value of a series reactance of the segment connecting the medium voltage line and the transformer.