GB583230A - Improvements in or relating to apparatus for electric brazing or the like - Google Patents

Abstract

583,230. Supply systems for resistance welding and the like. IGRANIC ELECTRIC CO., Ltd. March 1, 1944, No. 3871. Convention date, March 1, 1943. [Class 38 (iv)] A supply system for a spot welding or brazing transformer 6 includes in circuit with the transformer a variable reactance, such as a choke 10, the impedance of which is automatically increased at a controlled rate upon flow of current, so that the energization of the transformer is reduced as the welding &c. operation proceeds. The iron circuit of the choke may comprise a fixed portion 12 and a movable portion 13 pivoted to the former and constituting a yoke which is normally biassed away from the fixed portion by a weight 14. As the yoke is attracted to the fixed portion by current flowing in the winding 11, the inductance of the choke increases at a rate determined by a dashpot 15 connected to the yoke. The welding &c. operation is effected as follows : with the work 1 placed between the electrodes 3, 4, starting switch 18 is closed, thereby energizing a self-holding contactor 9 which connects the choke and transformer primary across the supply lines. Welding proceeds with diminishing current until the holding circuit of contactor 9 is interrupted by a stud 20 carried by yoke 13 opening a normally closed switch 19. In a modified arrangement, the choke is arranged to shunt current from a spot-welding circuit, so that the welding current is progressively increased. In another arrangement, a condenser replaces the choke as the variable reactance.