GB627646A - Improvements relating to apparatus for operating devices having a negative resistance characteristic from an alternating electric current supply circuit - Google Patents

Abstract

627,646. Protective arrangements ; control systems for arcs. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd., and WALKER, A. H. B. May 8, 1947, No. 12496. [Class 38 (iv)] In a system in which a D.C. or an A.C. are, fed from an A.C. source, is controlled by saturable reactors, the reactor control current is automatically reduced when the arc voltage falls below a predetermined value, thus limiting the arc current. The voltage across the D.C. arc A, Fig. 1, is applied via rectifier R2 to the D.C. control circuit of the reactors XI, X2, so that when the arc voltage falls below the control voltage, current flows from the control circuit into the arc circuit, thereby reducing the reactor control current due to the voltage drop in the regulating resistor 5. In a modification, Fig. 3 (not shown), the D.C. arc is fed from a three-phase rectifier which is supplied from a single-phase supply by a phase converter and transformer. The reactors are in parallel in one line of the input. In a further modification, Fig. 4, the voltage across an A.C. arc A is rectified by R3 and connected via rectifier R2 to the control circuit. A fall in the arc voltage allows rectifier R2 to pass current through a resistance 6 and so reduce the reactor control current. A three-phase arc, Fig. 5 (not shown), may be similarly controlled.