JPS57177879A - Generating method for plasma arc - Google Patents

Abstract

PURPOSE:To generate plasma arcs with plural phase AC voltages of low voltages without requiring intricate devices by applying the AC voltages between many non-consumable electrodes provided in the gaseous cup of a plasma welding torch and between the respective electrodes and base materials. CONSTITUTION:Three pieces of electrodes 29, 31, 33 such as W welding rods are disposed in a gaseous cup 35 at equal intervals in extreme proximity to each other so as to permit generation of inter-electrode arcs and in parallel in a triangular shape toward a nozzle port 28, thereby constituting a TIG torch 37. Three phase AC electric power is supplied between these three electrodes, and further base materials 39 are connected to the neutral point of said three phase AC electric power. Thereby, three interphase arcs 41 are generated among the electrodes, and arcs 43 are also generated between the materials 39 and the respective electrodes, thus six pieces of the arcs are generated simultaneously at the leading end of the torch 37. As a result, the central part in the leading end of the torch is heated to extremely high temp. and plasma 47 is generated between the same and the materials 39. This plasma is generated simply by supplying about 35V electric power and feeding gaseous Ar to the cup 35.