Striking a main arc between plasma and metal workpiece - using an auxiliary alternating current circuit

摘要

An auxiliary arc is struck between the electrode and the jet in the burner, using a high-frequency discharge, and plasma gas is fed to the burner so the flare bridges the gap between the electrode and the workpiece, thereby striking the main arc. The amplitude of the auxiliary high-frequency current must be at least equal to the desired value of the main current, and both the frequency and the pulse duty factor of the auxiliary current are adjusted so that a visualy controllable, steady flare is obtd. for the entire period in which the auxiliary current is used. The amplitude of the auxiliary current is pref. between I and 31 (where I is the desired value of the current in the main arc), and the pref. ave. auxiliary current is 3-10 A. Circuit is reliable, simple and cheap.