GB1174095A - Improvements in or relating to Electric Arc Furnaces - Google Patents

Abstract

1,174,095. Supply systems for arc furnaces. ENGLISH STEEL CORP. Ltd. 3 Nov., 1967 [4 Aug., 1966], No. 34911/66. Heading H2H. [Also in Division C7] In order to induce a refining action in an electric arc furnace 1 fed from an A.C. source 7, means are provided to superimpose a direct current upon the alternating current flowing between the electrodes 2 and the hearth 8, the direct current being obtained from either an external source 15 or from the self-rectifying action of the furnace. The electrodes 2 are normally supplied from the A.C. source 7 by way of a transformer 5. When the self-rectifying action of the furnace is to be utilized, a switch 13 is closed, whereupon a direct current will flow between the electrodes 2 and the hearth 8 by way of a circuit including an inductor 9. When the external source 15 is to be used a switch 21 is closed and the switch 13 left open whereupon the generator 15 causes a direct current to flow between the electrodes and hearth by way of the inductor 9. The windings on each leg of the inductor are divided into two counter-wound portions and are connected in pairs on different legs, thus preventing saturation of the inductor. The polarity of the voltage supplied by the generator 15 may be reversed by means of a switch 18 and the magnitude thereof varied by a potentiometer 20. If desired, the furnace may incorporate an auxiliary electrode and the direct current caused to flow between this electrode and the hearth. In a further arrangement the transformer 5 is provided with a star-connected secondary winding and a source of direct current connected between the star point thereof and the hearth.