A static phase converter will not do a thing for a transformer type 3
phase welder. It might do OK on an old rotary welder. Some one on
sci.engr.joining.welding NG tried a rotary phase converter. Seems to me
it didn't work as well as expected. I suspect that the inductive load
from the welder interacts with the nade up phase from the converter.
(Hmmmmm sounds like a GREAT final exam question for a EE major!)

But many of the transformer welders will run OK on 2 phase at 2/3rds
power. The output from the transformer goes to a massive diode block,
you are just missing one phase. Not as smooth as full 3 phase but
decent. You may have to experiment with which phase is dead since there
will be fans, control circuits, etc that will be running off a single
phase.

Specifics on which make and model you are looking at would be helpful.

Ignoramus15786 wrote:

Just confirming... there is no easy way to make a 3 phase welder run
on 1 phase power, is that right? I would need a full fledged phae
converter to run one, is that true?

i