GB604276A - Improvements in and relating to the art of electric resistance welding forging and heating - Google Patents

Abstract

604,276. Supply systems for resistance welding. SCIAKY, D. May 18, 1944, No. 9549. Convention date, Aug. 4, 1943. [Class 38 (iv)] A system for welding, forging and heating comprises a transformer, the primary of which is supplied with successive impulses of direct current which induce low frequency alternating current in the secondary connected to the welding electrodes. In a preferred arrangement the iron core is provided with an air gap. Impulses are derived from rectified A.C. and, according to Figs. 1 and 2, are controlled by maximum current relay 47 which effects intermittent opening and closing of contactors 31, 32 which are energized from a separate source through a starting switch 41 and auxiliary contactors 43. 46. Variation of the wave shape of the welding current may be effected by controlling ignitrons supplying the current or by taps on the primary winding of the welding transformer, controlling the turn ratio between primary and secondary. Modifications include : (1) the use of a timing device or devices in place of the maximum current relay ; (2) switches operated by a rotating cam arrangement 64, Fig. 6, which interrupts the supply to rectifier 77, and (3) an.alternative method of varying the wave shape of the welding current by means of a further cam whereby the voltage applied to the rectifier is reduced by inserting resistors before removal.