Made a 1/4" spark gap... I see sparks... Very exciting...
- posted
18 years ago
Made a 1/4" spark gap... I see sparks... Very exciting...
That's a neon xfmr. Three of those in series should make a dandy Jacob's ladder! The buzzzzzzzZZZAP noise it makes adds to the fun. With 3 or 4 of them in series, a Jacobs ladder should be able to sustain an arc over an inch long before it goes out at the top and starts again (ZAP) at the bottom.
The nameplate ratings can be confusing. They deliver rated voltage under open circuit conditions, rated current at short or near-short conditions. Once a spark/arc is initiated, voltage drops to about 1KV in a short gap. 1KV is a near short condition for a 30KV xfmr.
A job I once had was designing electronic oil ignition xfmrs, 30KV at
30 mA. They ran at about 30KHz. In normal use the rectified AC wasn't filtered -- but if a filter cap was added, the arc/spark was eery quiet -- just sort of a soft hiss. A Jacob's ladder with that was like the audio was missing.
Dang, so it really is a Franceformer, huh? Looks big enough to be very dangerous.
no no no no no no NO!!!! please don't put them in series. if you do that, you will very likely destroy one or two of them due to breakdown between the primary and secondary - look at it this way, all the primarys are in parallel (you plugged them in, right?), with the secondaries in series, there is around 27KV between the secondary of one transformer and the primary of the one farthest away (electrically). The primary to secondary insulation is designed for a 4.5KV standoff, with some safety factor, you are at 27 - not good, breakdown very probable. AND, if you are unlucky, you will find that the secondaries are center tapped with the center tap connected to the case.
Why risk good transformers. with 9KV and a jacob's ladder you start at about 1/4 inch at the bottom, you should be able to get an easy inch or three at the top - the plasma conducts much better than air.
Find one of the tesla coiling groups before you destroy these things, please.
bill n
Yeah, Ha ha, I thought the name was a typo/joke too.
Sounds interesting. I have 13 of them today. Maybe I will get more tomorrow. I forgot to pay for all the stuff I got today (and the owner forgot to ask me for money) and need to go there tomorrow to pay anyway.
Sorry, I digress.
I am confused by different statements made by different posters. Some say that they cannot be set in sequence because they are center tapped to ground. I am not so sure, since they can be mounted in isolation. Who to believe?
Yes. I just tried something interesting. I tried blowing at it. It made some big arcs and a corona discharge. Tomorrow, I may try to blow argon at it from my tig welder.
Very nice.
Well, sure, that's what constant current stands for, more or less.
The nameplate does not actually say what the output current is, AC, DC, HF, etc. I think that midpoint grounding pretty much implies AC. Not sure if it is 60 Hz or HF. My guess is that it is 60 Hz, both from the buzzing sound as well as the weight of this franceformer.
i
This does make sense. I think that I could try to acquire some glass cabinet on some stupid estate sale, or a cheap used fishtank, fill it with argon from my tig welder, and make some funny arcs inside.
i
Yes, this is a franceformer. I have about 4 franceformers, and 9 other brands, all very similar in dimensions and appearance. Total 13.
i
As it turns out, Franceformer is a company, a part of Scott Fetzer Co, which is itself a part of Berkshire Hathaway. I own a tiny bit of that company's shares, in fact.
i
This is somewhat related, since it involves a sign transformer. flames conduct electricity:
go here and learn a little about tesla coils - I'm trying hard to point you to a venue where you can make some $$ off those things - but I won't post more on the subject now - it's up to you - fragment of mail from listserv below:
Yes, they can theoretically be connected in series if you float the cores, but then you run into the problem that the cases are connected to the cores, the on/off switch is screwed into the case, the primary cable runs through the case, or (as William Noble pointed out), the primary/core insulation isn't rated for 4.5kV.
In other words, it's not practical given the structure and the voltages involved. Put one volt into the primary and it would work, but without significant reworking of the transformer itself (depotting/immersing in oil/reworking leads/insulating the primary), it isn't practical at 120VAC.
Jon
Huh?? Did I see the same pix?
All true -- but if you have 13 of them and they were cheap, how could you resist trying it with a couple? HV stuff is designed with pretty generous margins because insulation, etc degrades over time in the presence of HV.
My units are quite old, in fact. After carefully thinking about these issues, I realize that they cannot be put in sequence, unless I find some cheap isolation transformers. I get nice sparks with 9 kV, I can live with that for now.
i
Back in the stone age when I was doing science demos at a local science museum, we aquired a Tesla coil that used some monster old radio tubes rather than the spark gap system to generate the high frequency. As you said above, it was nearly silent while making foot long sparks. The sparks were more brush like (softer looking) than the standard spark gap unit we had.
The really cool thing about this unit was...no leaked low frequency in the sparks. You could stick your hand right in and not have the usual shock you often get from Tesla's. It did leave tiny pin prick RF burns on the surface of your skin (not deep enough to "feel").
As a demonstration piece, however, people in the audience really missed the snapping and crackling.
Koz (who once took a solid direct hit of a 3-1/2 foot tesla spark while well grounded and screamed "aww...FU**!" to an audience of kids as he jerked a couple of feet. )
Try quickly pulling a piece of typing paper through the arc. Do it fast enough that the paper doesn't light and you will see perforated holes showing that the arc is not continuous as it appears....after all, it is AC.
Koz (who did this as part of the science demos also....Kids have no clue that AC from your wall socket is not the same as DC from a battery)
I suspect they heard that word before..... Look at the bright side. At least you didn't expose them to something that would mar them for life. Like seeing you electrocuted (or pee your pants).
And I bet none of them burst into flames upon hearing it,either.
Or a half-second glimpse of a nipple during the superbowl half-time show or something. Now that, would be life-changing. Or something like that.
Seriously, a 3.5' spark...have you calculated the voltage for that? That could have been a game-over type event, no?
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