Electric arc welding

TLDR: In this article, the high-frequency inductor or transformer disposed in the welding circuit and necessary for the injection of the highfrequency current has a core of ferrite material or powdered iron and is arranged to saturate at normal welding currents so as to offer little impedance to the flow of welding current.

Abstract: 722,494. Supply systems for welding arcs. AIR REDUCTION CO., Inc. Dec. 8, 1952 [Dec. 28, 1951], No. 31074/52. Drawings to Specification. Class 38 (4). To permit the employment of a relatively low high-frequency (say 50 to 500 kcs. per sec.) current for starting and stabilizing a D.C. or low-frequency A.C. welding arc, the highfrequency inductor or transformer disposed in the welding circuit and necessary for the injection of the high-frequency current has a core of ferrite material or powdered iron and is arranged to saturate at normal welding currents so as to offer little impedance to the flow of welding current, but to be unsaturated by the high-frequency currents alone, so as to offer high impedance to these-and thus provide good injection of high-frequency currentwhen the arc extinguishes. The high-frequency generator may comprise a push-pull valve oscillator normally cut off by external bias, but triggered into oscillation by a voltage pulse induced in a winding of the injection transformer upon interruption of the flow of welding current.