ARC STARTER couppling?

Hi,
I'm currently building a complete WIG/TIG welder... microcotroller PCB
is runing and will be programmed probably next year (takes some
time ;-)
Currently I'm working on the arc starter.
I found an television high voltage transformer which has its resonance
frequency at 310kHz.. .I don't know why, but thie high frequency
works.
I get 3..4 cm at 12V and 2A... really lucky about that.
But I still failed to make the couppling from HV-side to the LV
welding lines.
There are several pictures available in the web with eg 20:20 turns...
every link says ... its running perfectly.
Here how I tried...
make 20:20 turns air coil with a diameter of app. 15mm...
connect one HV wire directly,
the second with a 1cm gap (no cap!)
No I was assuming to get a nice HV on the secondary side, but I get
nothing!
What is missing?... and why??
Please be so kind and tell me you opinion
If you have good links/suggestion... please post it
You can also write to snipped-for-privacy@web.de
If I get good suggestions, I will summarize everything here.
Thanks and have a nice day
Best Regards
powerfreak
Reply to
asdf81
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The typical TIG HV system has an old-style tesla coil circuit, with a 10 - 20 turn secondary that the torch lead is connected in series with. This produces a few hundred volts open-circuit and adds it to the torch open-circuit voltage.
Jon
Reply to
Jon Elson
Hi powerfreak
I have a Lincoln unit designed to make a stick welder to be used for TIG. I can take its lid off and send you some pictures of their method of coupling the HF to the welding cables. Lincoln aparently connects a low inductance , low resistance coil in series with the welding lead. That coil is the secondary of their HF transformer.
Jerry KD6JDJ
Reply to
Jerry
wrote: (clip) I get nothing! What is missing?... and why?? (clip) ^^^^^^^^^^^^^^^^^^^ At the frequency you are running, you probably have too much inductance in your little transformer. Couldn't you hook directly into your welding cable, so the HV goes in parallel to your welding voltage? Its purpose is just to ionize the air and get the arc started, and then you don't need it any more.
Reply to
Leo Lichtman
Points to ponder:
You finally got the 3000 to 10,000 Volts HF onto the welding cables to initiate the arc.
How are you going to prevent this Voltage from destroying the DC rectifier diodes and the insulation of the welding transformer??
What you need to consider is to place a 16 micro farad capacitor, AC service type, as a shunt across the welding current terminals; in effect this capacitor is in parallel with the bridge rectifier and the welding transformer, providing a HF short circuit path.
Also place .1 micro farad caps in parallel with each individual rectifier.
Don't ask how I know, but AC service capacitors, while expensive, are cheaper than 250 Amps / 300 Volt rectifier diodes. :-)) My son converted a Lincoln tombstone AC buzz box into a full blown AC/DC TIG machine with foot pedal current control and HF arc starter. Nice machine.
Wolfgang
Reply to
wfhabicher
You're over an order of magnitude too low in frequency. 8 MHz is more in the ballpark.
Reply to
Don Foreman
My Thermal Arc will jump a good inch and a half, which would be about 6500 volts AC.
Reply to
Jim Stewart
I always turn my arc starting to a low setting, enough to jump 2 mm or so. Much more comfortable.
i
Reply to
Ignoramus11945
Hi together, thanks for the hints, I'll try and report again... please do continue to post recomendations, links or pictures and feel free to contact me directla Thanks powerfreak
Reply to
asdf81

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