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Registered Member #1806
Joined: Sun Nov 09 2008, 04:58AM
Location: USA
Posts: 136
Sorry for the question. I was thinking that you are designing a starter for a xenon arc lamp. Now I read again all the posts and I conclude that your project is for a welder machine. Can you confirm ??
Confirmed. My goal was for a welding machine.
As I said before, the ignition pulse of 0,006 joules is enough to start the arc. The pulses reaches 15000 volts during 0.5 to 1 microseconds at the welding torche / electrode. This pulse produces a spark of 3-4 mm in the open air or 12mm in argon/welding atmosphere (cool electrode, cool atmosphere ). Also you can touche the electrode, see the sparks going to yours fingers and you do not fill any electrical shock.
I like those specifications. The low energy will limit its radiated EMI (something I hear can be quite a problem) and like you said, will limit the heating in the spark gap. I have seen videos of that where people run the HF to their hand; it's just incredible.
Also read the concepts of a arc starter written @ Google Patents, patent 2880376, by Franz Tajbl. It is the bible for construction of arc starters. The main concepts and technics for arc starter are spelled out. Of course, the saturated core tranformer used in that patent is something superseed.
you for the link. That is very interesting reading.
PS: How can I attache a small clip video in this reply ??
If the video is on your computer, and it is a .mpg or .avi, you can attach it using the dialog when composing a reply. If the video is hosted somewhere such as YouTube, you can simply link to it.
Registered Member #3343
Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311
Here is the video!
]10kv_in_the_hands_dscf0165.avi[/file]
It shows the sparks running over a calibrated air gap. When the screw drive get closer, the sparks leave the air gap and jump tp screw drive.
The calibrated gap is used to measure the HV pulses. The needles under HV are "screwed" closer, and when the sparks disruped the air the distance between the needles is measured. The peak voltage then may be calculated using the formula: Upeak = D x 4000 Upeak is in V D is measured distance, im mm.
This is the formula usefull for 1000 to 20000V. Of course, normal conditions of temperature and pressure.
I hope the "apparatus" may be helpfull to other HV members
Registered Member #3343
Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311
3L3:
I did have any measurement of EMI that may be produced by the arc starter apparatus. Of course, a electricalmagnetical field is produced (and irradiated) at each spark pulse.
To be precise, the energy in each pulse not is really low. It is 0.006 joules, energy enough to disrupt 6mm of air gap. The treak is that the circuit just give one pulse each half of one 60 Hz period. (just one pulse each 8.33ms). And synchonized and at exact time. This is enough to trigger the 50-75V supplied by buzzbox or even the tig apparatus...
The old arc starters use a 3600V transformer with a shunt reluctance to limit the secondary current to 30mA. This arrangement produces 30 pulses at each 8.33ms... It is a waste of energy, because it is nescessary just one pulse to start the arc. All other pulses absorves energy from the power supply and demands a 100 to 300VA tranformer. Also the spark gap fires 2x29 uselles sparks per period, demanding a heat sink.
Just give a list with the parameters to be specified, I will try to answer.
Registered Member #1806
Joined: Sun Nov 09 2008, 04:58AM
Location: USA
Posts: 136
Newton,
Thanks for posting the video. That is very interesting. The output looked similar to the one I built (on the occasion that it happened to work at all). Did you feel anything when it jumped to the screw drive? What was the black wire connected to the right side of the air gap? Was it an RF ground of some kind?
About me saying it has low energy. I spoke poorly. It has low energy as compared to others that run continuously and also dissipate more heat in the spark gap. So this is good. It is just powerful enough to get the job done without being excessive and needing spark gap cooling and producing more EMI than necessary.
Registered Member #3343
Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311
Hi 3L3:
I do not fell any sensation when touching the sparks. Sometimes when Im welding, during the electrode exchange, not intentionally, I touch the electrode holder, and I saw the sparks... but I did not feel any sensation.
The black wire is 2 turns primary wind, conectec to spark gap and HV cap. Pls follow the schema attached in the previous post.
No RF grounding at this preliminary test. Only when the arc starter is attached to the buzzbox. a loop of 2-3meter #14awg on the floor or nailred in the wall. Or just use any metalic mass. Also conect to buzzbox frame.
I have some difficulty to post pictures and organise information for the forum. Can you send your email, it wiil be easer to put the information in the proper way ??
Regards
Newton .
Pictures: 0.5mm SPARK GAP and PARAFERNALIA TO MEASURE THE SPARK kVs MEASURING THE SPARKS KV GLASS CAP and MMC THE TEST ASSEMBLY
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Alternative high voltage coupling - sparkgap to solid state.
