In older machines, a balanced current output wave was achieved using a large number of capacitors in
series or a battery in the welding circuit. Modern TIG power sources use electronics to create and maintain
a balanced wave and now most AC TIG power sources produce a square wave current output.
A square wave power supply can change the current from electrode + positive to electrode - negative very
quickly. This produces high voltage as the current switches polarities allowing the arc to restart easily. The
arc can be maintained without the use of high-frequency or any other arc stabilising methods.
The output current and voltage are controlled electronically so the balance between the amount of current
electrode positive and the amount of current electrode negative can be adjusted. This allows the welder to
adjust the amount of cleaning and the amount of penetration. This is achieved electronically by adjusting
the balance control dial on the welding machine. More current ow from the + polarity produces stronger
arc energy and current ow from the tungsten and is good for removing the oxidized surface of the work
piece. However too much + current ow can drive too much energy to the tungsten causing it to overheat
and melt the tungsten electrode.
BALANCED SQUARE WAVE FORM
Balance Adjusted for More Oxide Cleansing Action - Hotter Tungsten
Balance Adjusted for More Penetration - Cooler Tungsten
Even Penetration - Stable Arc
More Penetration - Faster Welding
More Electrode Capacity
Less Penetration - Oxide Cleaning
Less Electrode Capacity
AC TIG Welding - AC Wave Balance Control