tig hi freq

Work on your google-fu. Does this help? My first hit.

George H.

George - thanks for looking. That article is about the frequency of the current that provides the power for welding aluminum. Apparantly aluminum can't be effectively welded with a dc current as is the case with steel. My present understanding for tig welding of steel is that a high frequency low powered "starter" current establishes a low resistance pathway for a high amperage dc current. It is this starter current that's of interest and not the high amperage ac current used with aluminum.

Hul

George Herold wrote:

FWIW I sometimes find Google no use, but get useful results from other search engines.

NT

Den mandag den 27. marts 2017 kl. 18.15.37 UTC+2 skrev Hul Tytus:

negative electrode puts most of the heat into the part instead of the electrode but that doesn't work for aluminium because you need some current flow the other way to clean the metal.

I don't think there is any specif frequency for HF start, it is just a high voltage at a frequency that can be coupled to the welding voltage to start an arc instead of having to scratch start

there a diy versions made with old ignition coils

It's about 80% political crap these days, but if you're willing to spend some effort setting up your killfiles, this would be an excellent question for rec.crafts.metalworking. That group has everything from grumpy old retired machinists (which is the doorway to the political crap, AFAIK) to working manufacturing engineering types.

Someone there will know.

I looked for the rest of the article on Hackaday, but didn't find it. Do you happen to have a URL for it? TIA, Bill M

Even better is sci.engr.joining.welding. Ernie will know. But he does not read the group every week.

Dan

On Monday, March 27, 2017 at 12:15:37 PM UTC-4, Hul Tytus wrote: Apparantly aluminum

Actually aluminum can be welded with dc current. But it is not as easy.

Dan

Hire one for a day and measure its output characteristics for yourself.

OK... As Tim W. said try rec.crafts.metalworking. Or the group Dan mentioned. (I don't know that one.)

George H.

The typical setup on older welders is a spark gap Tesla coil, so there is no control of frequency. A several thousand Volt transformer charges a capacitor at 60 Hz frequency, that voltage creates sparks that dump the capacitor into the Tesla coil primary. So, the output is generally bursts of 10-20 KHz spikes repeated at 120 Hz.

Some newer welders have electronic drive for this, so they have a defined frequency.

The HF on a TIG welder ought to be at least 10 KV, and maybe up to 20 KV.

Jon

I would ask at > sci.engr.joining.welding < They do welding and it has no political fun!

Mikek

Good idea, Tim. Thanks.

Hul

Tim Wescott wrote:

Thanks Dan. I posted the question there.

Hul

snipped-for-privacy@krl.org wrote:

Next step for sure.

Hul

Cursitor Doom wrote:

Jon - any suggestions on which of the newer tig welders has the more modern hi freq drive?

Hul

J> > sci.electronics.design

Measuring the frequency may be easy as it can be done from a distance, but measuring the voltage is probably not so easy. It is something like a small tesla coil, but with a very stout secondary so that it won't overheat with the welding current also passing through it. Like a tesla coil, I would be unwilling to connect it to my good oscilloscope without a trustworthy high voltage probe rated for much higer voltages than I expect. A high voltage scope probe good to high frequencies is not trivial to build and not cheap to buy.

You could make an approximate measurement of the voltage by seeing how far away it can initiate a spark, but then again you could just skip any measurement and decide how far you want it to be able to initiate a spark and look up the voltage that you would need for that.

Well, if it is the size of a lunchbox, it must be the modern style.

I have an 800 Lb Lincoln Square Wave TIG 300, so that is definitely the OLD style. It is the size of a small fridge. The HF is strong enough you can weld really thin stuff with just HF!

Jon

Jon - good gage. I'll keep that in mind.

Hul

J> > Jon - any suggestions on which of the newer tig welders has the more