Pulsed-arc D.C. TIG welding apparatus

DETAILED DESCRIPTION This invention relates to the pulsed arc welding technique and particularly to an arc welding apparatus for pulsed arc welding.
The invention is intended to provide a new and improved apparatus for this purpose which has an improved control rate and low power losses.
It is a principal object of the invention to provide an arc welding apparatus whcih comprises an A.
C.
power supply, a SCR system provided with A.
C.
terminals connected to said A.
C.
power supply and with D.
C.
terminals connected by a first and second current conductor to a non-consumable electrode and a workpiece, respectively, to maintain an arc between said electrode and said workpiece, one of said first and second current conductors connecting an inductor in series with the eletrode for smoothing the welding current delivered from said SCR system, a D.
C.
power supply connected in parallel by a third and a fourth current conductor to said non-consumable electrode and said workpiece, respectively, one of said third and fourth current conductors containing transistor means in series to said electrode, means for producing an adjustable control signal to regulate the flow of current through said transistor means when being in their conducting state to provide periodically recurring welding current pulses of predetermined length and amplitude in addition to the welding current delivered by the SCR system.
The transistors are loaded only by the short pulse currents in addition to the background current.
The pulses have a rectangular waveform and their duration, frequency and amplitude can easily be controlled.
The background current is delivered from the SCR unit and causes only small losses.
Another object of the invention is to provide an arc welding apparatus which comprises an A.
C.
power supply, a SCR rectifier system provided with A.
C.
terminals connected to said A.
C.
power supply and with D.
C.
terminals connected by a first and a second current conductor to a non-consumable electrode and a workpiece, respectively, to maintain an arc between said electrode and said workpiece, one of said first and second current conductors connecting an inductor in series with the electrode for smoothing the welding current delivered from said SCR system, a D