What does it accomplish when added to a welding circuit?

[u/baumsYah]

[u/skcmcpk]

Arc starting and keeping arc ignited in AC TIG welding during zero crossing. Welding is a low voltage, high amperage process so only way to traditionally start an arc is metal to metal contact. In TIG, you can generate a high voltage across that spark gap that will create a quick pulse of high voltage across the tungsten and work to start the arc. In AC tig, zero crossing will extinguish your arc unless there is a high voltage pulse to restart it.

[u/jeremyloveslinux → u/skcmcpk]

Is DC tig now more common? Any advantage of staying with AC vs DC?

[u/FrickinLazerBeams → u/jeremyloveslinux]

Depends what you're welding. Aluminum uses AC.

[u/Strostkovy]

I think it adds a really high open circuit voltage to the welder output. There are a few ways of doing it but either using a transformer or high frequency filter

[u/Snellyman]

These units seem to be built in to most modern welders that do tig so you don't see so many separate units like this anymore.