GB439900A - Improvements relating to the art of electric arc welding - Google Patents

Abstract

439,900. Automatic regulation. DEHN, F. B., 103, Kingsway, London.-(Carter, R. W. ; c /o Hume Pipe (Far East), Ltd., Hong Kong, and Hume Steel, Ltd. ; Kinnear House, King Street, Melbourne, Australia) July 10, 1934, No. 20275. [Class 38 (iv)] In electric arc welding in which A.C. is used, the rate of feed of the fusible electrode to the work is automatically controlled in accordance with fluctuations across the arc by regulating the speed of a D.C. motor which drives the electrode feed mechanism and is supplied with rectified current from an A.C. circuit in parallel with the arc circuit. A.C. is supplied to the electrode 3 and the work 4 from the secondary of welding transformer 2. The armature 22 of the electrode feeding motor is supplied with D.C. from a full wave rectifier 6, the plates of which are connected to the secondary of the transformer 7, the primary of which is connected by leads 11, 12 across the arc circuit. The voltage drop due to the striking of the arc causes contacts 14, 16 to close by means of a relay or electromagnetic device 8. A variable resistance 17 introduced by a switch 19 is associated with the operating coil 18 of the electromagnetic device. Variable resistances 26, 27 facilitate initial adjustments of the potential to the armature. The field 28 of the motor is supplied with non-variable D.C. from an independent source or, as shown, from a full wave rectifier 31, the plates of which are connected to the secondary 32 of a transformer having a primary connected across the main supply, this transformer being also associated with the rectifier 6. An adjustable resistance 36 is interposed in the motor field circuit. In a modification, the field of the motor is excited from an independent source.