GB1349080A - Current control arrangement in a seam welding assembly - Google Patents

Abstract

1349080 Automatic current control KOCKUMS MEKANISKA VERKSTADS A B FACK 19 April 1971 [5 Feb 1970] 21736/71 Heading G3R The output current of seam welding equipment is maintained constant by a control system comprising a transistorized/thyristorized type of voltage regulator 11 which is supplied from a mains unit 10 and supplies a welding protector or guard 12 for adjusting the welding current to a desired value, the current from member 12 being sensed by a current transformer 14 whose output is passed to an amplifier 16 and thence to a control unit 17 supplying pulses to the regulator 11. Thus the latter is controlled so that a constant current is obtained in the secondary circuit of the welding transformer whose primary winding is connected to conductors 13. An ammeter 15 or equivalent resistance suppresses transients in the output of transformer 14. To prevent unwanted adjustment of the regulator 11 when the secondary of the welding transformer is opencircuited, a limiting circuit comprising a diode 18 and a potentiometer 19, 20 is provided, the latter being connected to potentials V r and V k Thus upward adjustment of the voltage regulator is stopped when the feedback signal from amplifier 16 reaches the reference potential set by adjustment of the resistor 20, upon which the diode 18 becomes forward biased. During short circuiting of the transformer secondary, unlimited downward adjustment of the regulator occurs.