I am hoping you people can shine some light on this problem I'm having with trying to AC TIG weld Aluminium.
I am using a home built high frequency unit (based on a Miller HF15) with a AC transformer stick welder (230 volt primary supply, 46 volt open circuit secondary, 50-160 amp) and pure Argon with 2.4mm zirconiated tungstens. Normally when stick welding I can run it at 160 amp if I'm careful, and not blow the 15amp fuse in the shed fuse box.
The problem is when I try to TIG Aluminium I can't "dial in" over about 80 amps on my power source with out blowing the 15 amp fuse. I am putting this problem down to partial rectification producing a DC current that the welder is trying to overcome by drawing extra current in the primary. The welder gets hot quite quickly resulting in the temperature overload kicking in. I am wanting to get to at least 125amps so I can try and weld 3mm (1/8 inch) aluminium.
I have tried including a 12 volt battery (as per Lincoln Electric recommendations) in the welding circuit but soon removed this due to the large amount of hydrogen gas produced and rapid rise in temperature of the battery.
Have also tried my mates stick welder as the power source, it's a little more "industrial" than mine, same problem.
So my question is, does anyone have any suggestions to overcome / reduce this problem. Or is there something other than partial rectification causing the problem?
Thanks in advance, questions welcome.