Abstract: A method for the optimum regulation of the electrodes of a three-phase electric arc furnace wherein each electrode has an associated arc voltage regulator which receives the associated arc voltage as its actual value and a desired arc voltage value as its reference value; and wherein, to form the desired arc voltage value, during each halfwave, a voltage porportional to the actual arc current and a limit value, which corresponds to the desired arc length, are provided, and the smaller momentary value, with respect to magnitude, of the current proportional voltage and of the limit value is always fed to the arc voltage regulator as the desired arc voltage value.

Abstract: A method and apparatus for regulating an arc discharge furnace having a lining, a plurality of electrodes disposed above a bath of conductive material, an adjustable transformer for applying to each electrode a voltage which causes an arc current proportional to the applied transformer voltage to flow between the electrode and the bath, a device for varying the voltage applied by the transformer to each electrode, and a device for varying the vertical spacing between each electrode and the bath. Desired values for a maximum of two of the following parameters are selected: the voltage of the arc current produced by one electrode; the arc current produced by the one electrode; the power of the arc produced by the one electrode; a parameter which is proportional to the wear caused to the furnace lining by the arc produced by the one electrode; and a correcting variable for the voltage applied to the one electrode by the transformer.

Abstract: A method and apparatus for electrically balancing the phases of a three phase arc furnace, the furnace having a vessel containing a molten bath, three electrodes above the bath, and a transformer arrangement composed of three phases, each phase including a winding, the transformer arrangement being connected to the electrode so that each electrode conducts an arc current proportional to the voltage across the winding of a respective phase, by the steps of: matching the voltages between the electrodes and the bath to one another by adjusting the spacing between at least one electrode and the bath; and establishing symmetry among the arc currents by: varying the voltage across at least one phase winding by a selected increment; measuring the arc current amplitude in the electrode associated with the at least one phase winding after each variation step; and repeating the steps of varying and measuring until the differences between the arc current amplitudes of the three electrodes are less than a given value.