GB716596A - Control arrangements for pre-magnetised transformers - Google Patents

Abstract

716,596. Automatic current control systems. LICENTIA PATENT-VERWALTUNGS-GES. Dec. 17,1952 [Dec. 17, 1951; Feb. 21, 1952], No. 31989/52 Class 38(4) The current in a load circuit (particularly a welding circuit) supplied from a frequency multiplying transformer having a Scott connected three-phase primary and a single-phase secondary as disclosed in Specification 714,146, [Group XXXII], is maintained substantially constant by varying the saturation of the transformer core in accordance with either load current or load voltage. In addition to the primary and secondary windings (not shown) the transformer V, Fig. 2, has opposed saturating windings. H, G. The reference winding H is energized over rectifier G1 from the supply mains and the winding G is energized by the amplified resultant of a voltage proportional to load current derived from current transfomer S and rectifier G2 and a reference voltage derived from rectifier G3. Thus any increase in load current reduces the nett saturation to restore the current to the required value. In another embodiment, Fig. 5, the primary and secondary windings are again not shown and the reference winding H is aided by the winding Z which is energized over a rectifier in accordance with the load voltage. A choke Dr operating in its non-leiriear range may be included to improve the accuracy of regulation.