GB202063A - Improvements in and relating to electric control systems for arcing electrodes - Google Patents

Abstract

202,063. British Thomson-Houston Co., Ltd., (General Electric Co.). May 17, 1922. Regulating, automatic systems and apparatus for.-An electric control system for arcing electrodes includes an electric valve connected so as to be responsive to the electrical condition of the arc, and electroresponsive means, controlled in part by the valve, for regulating the arcing relation of the electrodes. An electric furnace 13 is provided with electrodes 10, 11, 12 supplied with current from the secondary of a transformer 32, the primary of which is supplied with current by leads 31. The electrodes are operated by motors 14, 15, 16 having separately-excited field windings and supplied with current by generators 27, 28, 29 driven by a motor 30 energized from the leads 31. Each generator has a pair of differentially-wound and separately-excited fields 35, 34. The field 35 is supplied with current from an exciter 33, and the field 34 comprises part of a circuit which includes an electron discharge valve 17 and the secondary of a transformer 23. The primary of the transformer 23 is formed in each case by a coil in the lead supplying current to one of the electrodes. The valve 17 comprises a plate 21 and a hot cathode 20 connected across a portion of the secondary winding of the transformer 23, and including an adjustable resistance 26 in the circuit. These resistances 26 are adjusted so that, with normal arcing relationship of the electrodes, the plate current of the valve is such that the fields produced by the windings 34, 35 neutralize one another. An increase in the current supplied to the electrode 10 produces a corresponding increase in the voltage of the secondary of the. transformer 23. The heating effect of the cathodes 20 is thus increased with a consequent increase in the current in the plate 27 and the winding 34. The balance between the fields produced by the windings 34, 35 is thus destroyed, and the generator 27 supplies current to the motor 14 to raise the electrode 10. If the current to the electrode 10 decreases, the plate current in the corresponding valve decreases. The motor 14 is then supplied with current in the reverse direction, and operates to lower the electrode.