GB907205A - Improvements in or relating to arc initiation - Google Patents

Abstract

907,205. Control systems for welding arcs. SATURN INDUSTRIAL GASES Ltd. Oct. 5, 1960 [Oct. 5, 1959], No. 33747/59. Class 38 (4). A D.C. arc between electrodes 1 and 2 is initiated by high potential pulses applied, preferably through a spark-gap 20, to the electrodes from the secondary winding 19 of a step-up transformer 11 having a primary winding 10 which is intermittently connected to a condenser 5 charged from the D.C. power supply 4 feeding the electrodes. A contact 9 is controlled by relay winding 13, driven from an oscillatory circuit 13-15 when contacts 6 and 17 are closed. The intermittent current through primary winding 10, thus caused, may instead be produced from the D.C. power supply 4 by means of a solid state controlled rectifier or an avalanching diode. The circuit may be arranged so that the intermittent primary current for winding 10 ceases when the arc is struck. Thus contact 17 may be broken by means of a current or voltage-sensitive winding in the arc circuit or by arranging that there will be insufficient voltage available from the power supply 4 to maintain the intermittent potential under cooling conditions. The arc initiation circuit may be arranged to produce pulses which are of short duration and of the same polarity as the potential of the connections from the D.C. power supply to the electrodes. The contact 6 may be incorporated in the arc initiation circuit to render it inoperative, and may be mounted on the electrode holder. An A.C. operated solenoid controlled gas valve may be used to provide gas shielding for the arc.