38
AC TIG Welding - AC Wave Balance Control
Razor
32OAC/DC
TIG-MMA
In older machines, a balanced current output wave was maintained using several capacitors in series or a battery in
the welding machine. Modern inverter based 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.
An AC TIG power supply with Square Wave output can change the direction of current flow from Electrode Positive
to Electrode Negative almost instantly. This fast switching speed results in high voltage as the current switches polar-
ity, allowing the arc to retain stability without the use of continual HF or any other arc stabilising methods. HF is still
retained for the initial ignition of the TIG welding arc as the preferred method of arc starting.
In modern AC TIG machines, the current polarity changes between Electrode Positive and Electrode Negative is con-
trolled electronically so the balance between each can be adjusted manually by the operator. This allows adjustment
between the amount of cleaning action and the amount of penetration. Adjusting AC Balance to give more time in
the Electrode Positive phase produces more current flow from the workpiece to the Tungsten and increases the de-
oxidisation or cleaning action of the workpiece surface. Electrode Positive current also results in more heat being driven
into the Tungsten Electrode and excessive Electrode Positive can still result in the Tungsten overheating and melting.
BALANCED SQUARE WAVE FORM
Balance Adjusted for Higher Oxide Cleansing Action - Hotter Tungsten
More time spent in p polarity cycle
reverse polarity
current
direct polarity
EVEN BALANCE
Even Penetration - Stable Arc
LESS POSITIVE
BALANCE
More Penetration - Faster Welding
More Electrode Capacity
MORE POSITIVE
BALANCE
Less Penetration - Oxide Cleaning
Less Electrode Capacity
EVEN BALANCE
Even Penetration - Stable Arc
LESS POSITIVE
BALANCE
More Penetration - Faster Welding
More Electrode Capacity
MORE POSITIVE
BALANCE
Less Penetration - Oxide Cleaning
Less Electrode Capacity
25%
current
direct polarity
reverse polarity
current
For many years, much of the AC TIG welding equipment available did not have the luxury of adjusting AC Balance. The
balance was typically fixed at a 50/50 percentage, with half the cycle time on Electrode Positive and half the cycle time
on Electrode Negative. Such a high duration in Electrode Positive would cause the Tungsten Electrode to become very
hot and often result in the tip melting and dropping into the weld puddle. To help mediate that problem, welders would
prepare the tungsten by melting or “balling” of the tip on a scrap surface before welding. This preparation allows the
Tungsten Electrode to better cope with the excessive heat generated in the excessively long Electrode Positive phase of
the AC cycle. In modern AC TIG machines that is no longer an issue as AC Balance allows us to reduce the cycle time
in Electrode Positive, making it unnecessary to ball the tungsten before welding.
Summary of Contents for RazorWeld Razor TIG320 ACDC
Page 7: ...7 Electrical Schematic Diagram Razor32OAC DC TIG MMA...
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