Ac Welding; Waveform - EWM L2.00 DC Expert 3.0 TIG Operating Instructions Manual

5.1.4

AC welding

The welding of aluminium and aluminium alloys is made possible by the periodic change of polarity on the
tungsten electrode.
The negative pole (negative half-wave) of the tungsten electrode determines the penetration characteris-
tics and has a lower electrode load compared to the positive half-wave. The negative half-wave is also
called "cold half-wave".
Whereas the positive polarity, i.e. the positive half-wave, breaks up the oxide layer on the material sur-
face (the so-called cleaning effect). At the same time, the tungsten electrode tip melts into a ball (the so-
called balled end) due to the high thermal effect of the positive half-wave. The size of the balled end de-
pends on the length (balance setting > see 5.1.4.3 chapter) and the current amplitude (amplitude bal-
ance > see 5.1.4.5 chapter) of the positive phase. It should be noted that a balled end that is too large
may lead to an unstable and diffuse arc resulting in a low penetration profile. Therefore, the relationship
between the current amplitude and the balance of the task must be adjusted accordingly.
Selection
AC settings

Waveform


Frequency

Balance

 Amplitude balance
 Commutation optimisation (AC)
Lock the window in place

5.1.4.1 Waveform
With the waveform parameter, three different alternating current waveforms can be selected to fit the ap-
plication:
• Square - highest energy input (factory set)
• Trapezoidal - an all-rounder, suitable for most applications
• Sine - low noise level
099-00L200-EW501
13.05.2022
Functional characteristics
Figure 5-7
TIG welding
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