GB796786A - Electrical converting system for supplying welding apparatus - Google Patents

Abstract

796,786. Converting. WELDING RESEARCH, Inc. April 22, 1955 [May 3, 1954], No. 11636/55. Class 38 (2). In a welding system of which the welding transformer 19 has three primary windings 16, 17, 18 each connected between a respective pair of the lines 11, 12, 13 of a three-phase supply system in series with a pair of reversely connected ignitions 23, 24; 28, 29; 32, 33, the provision of inductors 21, 22; 26, 27 ; 30, 31 accelerates the rate of reversal of current between oppositely directed pulses, Fig. 4, by allowing it to occur before the energy stored in the circuit inductance could be dissipated by natural losses. The inductors also limit circulating current and prevent short-circuiting of the power supply following the use of two groups of ignitions. The efficiency of alternating pulse welding is thereby increased, the weld having less time to lose heat between pulses. The inductors may be formed by centre-tapped coils wound on a common core 25. Each ignition is impulsed by the discharge of a condenser 38 through a transformer 36 when its associated thyratron 35 is fired. The grids of the thyratrons 35 are energized from pick-up coils 43, 44, 45 and 49, 50, 51 which are moved in the fields created by coils 40, 41, 42 and 46, 47, 48 energized from the three-phase supply. The movement is effected by a piston 55 moved under the control of a master control 70 which supplies a selected number of pulses of appropriate frequency and duration to control 73, which by energizing coil 66, operates valves 59, 60 against spring 67. The instants at which the ignitions are fired, and thereby the power supplied to the weld, are determined by the setting of piston stops 63, 64. Specifications 654,583 and 674,042 are referred to.