GB809124A - Improvements in electric arc welding systems - Google Patents

Abstract

809,124. Electric welding systems. FOSTER TRANSFORMERS Ltd., and JENNINGS, R. E. March 28, 1956 [March 29, 1955], No. 9122/55. Class 38 (4). A main welding transformer 1 is connected through a regulating inductor 2 to a tapped transformer 3 having a bridge rectifier 4 connected across a portion of its winding to provide a low-voltage D.C. source with a short-circuit current of comparatively high value. These electrical characteristics are suitable for gasshielded continuous feed welding. Smoothing of the direct-current waveform is obtained by means of the series inductor 2 or, alternatively, a high-voltage tapping on the transformer 3 is connected through inductor 5 to a rectifier 6 the output of which is in parallel with that of the rectifier 4. The phase angle of the current in the rectifier 6 is retarded so that the combined currents of the two rectifiers never fall to zero. The current drawn from the rectifier 6 is sufficient to maintain the welding-arc and is only a fraction of the main current. Without using the rectifiers, and taking a supply from an intermediate tapping of the transformer 3, the equipment may be used to provide low-voltage A.C. and high short-circuit current. Additional windings 31, 32 may be provided on the transformer 3 for connection to rectifiers 41, 61, which are arranged to be connected in series or parallel for high-voltage or low-voltage operation respectively. The main and additional transformer windings may be combined to form a centretapped auto-transformer winding suitable for use in a double electrode A.C. welding system. Thus, a supply lead is connected to the centre tapping and the two end terminals of the transformer winding are connected to the respective electrodes, Fig. 3 (not shown). Equipment comprising the tapped transformer 3 having an auxiliary winding 34, together with rectifiers 4 and 43, may be set for low- or high-voltage D.C. welding, low- or high-voltage A.C. welding, or double arc welding by adjustment of multiposition switches A, B, and C, and by connecting different links to certain of the terminals a . . . h, the electrode E1 being used only for double arc welding.