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question re: stepping up ignition coils

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LAN_403

Sulaiman

Wed Oct 03 2007, 08:07PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

A 'trick' that is used for impulse generators is-
e.g. Xenon trigger coil, tazer etc;
If you apply a large voltage across the primary it will very quickly saturate the core
during the brief period that the core is not saturated it behaves as a transformer
providing a brief high voltage output following Vsec = Vpri x (Nsec/Npri)

It may not be efficient but it works.
so for example in a typical disposable camera flash unit
a 10 nF capacitor is charged to about 300 volts and discharged into the trigger coil primary.

Doubling the capacitance would not give more voltage OR a longer pulse
it would just stress the wire of the primary more.

thrival

Wed Oct 03 2007, 11:52PM

Registered Member #1019 Joined: Sat Sept 22 2007, 02:39AM
Location:
Posts: 29

Neil--

I DID post the links. They appear as little green arrows (above) or say "image disabled."
I don't know why links appear this way, I copy paste the URL's but they don't appear that
way.

Output of an ignition coil is low current, high V, so to step that up several times is what I'm
about. Air-core is fine if it'll work. All it has to do is mirror input but at a higher V. Looking for
a simple way to wind a transformer, say 1:10 turns ratio and run these in series till I get say
100kV, but without using miles of copper. Reading up about baluns and trying to understand
why this can't work.

Steve Ward

Thu Oct 04 2007, 12:59AM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Im just waiting until you realize that the solution to your question is in fact to just build a typical tesla coil.

thrival

Thu Oct 04 2007, 01:54AM

Registered Member #1019 Joined: Sat Sept 22 2007, 02:39AM
Location:
Posts: 29

Steve--

Too big! Tesla coil not the solution to every problem, even tho I DO understand
how they work! (Believe it or not.)

Myke

Thu Oct 04 2007, 07:35AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

Not all Tesla coils are big. ShawnLG made a very small Tesla coil that actually worked. I would have to agree with Steve, just build a Tesla coil. You could do something like TDU did which was to use the ignition coil as a pulse transformer but they tend not to last long.

Dr. Slack

Thu Oct 04 2007, 08:51AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Neil--

I DID post the links.

Oh, those links. I did have a look at those before I posted. What I meant was, post exactly what you were referring to. I've found several transformers on that site. There's one with 300kV output with a pulse repetition frequency of 300Hz. BUT, it has a pulse width of 3.5uS, and the frequency I referred to earlier was not the pulse rep frequency, but 1/flux reversal time, which is the bit that matters when generating the output voltage. At a mean power handling of 40kW, I don't think it would meet your criterion of compact. There's no scale on the picture, but it would probably take a truck to move it.

There are others, all of which have plausible sounding ratings for their size.

Drill down to the specific one that you think does huge numbers of volts at small size and low frequency (flux change frequency, not PRF), and post the link to that.

Marko

Thu Oct 04 2007, 12:20PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Too big! Tesla coil not the solution to every problem, even tho I DO understand
how they work! (Believe it or not.)

Thrival, that is the hardest and first step you need to do now. Once you get into TC's you'l realize pointlessness of this thread.

Common ignition coils may produce few inch sparks and the they will break down, and there's nothing you can do about it.

Your ideas about seriesed transformers just won't work, 4hv'ers already explained you why.

Tesla coils have superior voltage standoff capabilities, and can easily be made into any size you want.
When you master it all you'll return and laugh at this thread - just as I did many times - guys over here definitely know a lot about what they are talking about.

Marko

thrival

Thu Oct 04 2007, 04:15PM

Registered Member #1019 Joined: Sat Sept 22 2007, 02:39AM
Location:
Posts: 29

Neil--

I DID post the EXACT links, if they didn't show up, I cannot help it. One was called a voltage
divider, but from its brief description, believe it to be an auto- transformer with 1:5000 turns
ratio and a peak voltage of 300kV. It doesn't look very big to me. Other was for a "pulse
current mutual inductor" Specificationï¼š

Tr=1ÂµS~2mS
F=1Hz~100KHz
Primary peak valueï¼š1A~1000A
Secondary currentï¼š1ÂµA~100A
Isolation potentialï¼š100KVDC

The above look to be two potted transformers, again not too big.

Myke & Marko:

Well it wouldn't be the first time if I had to laugh at myself. Anyway if Tesla coils can be
made small (which is what I want), where's the disagreement? However there is a
contradiction in that notion. Someone accused me in a different post of an ebay item,
claiming it was just a flyback and not a real TC. Anyway if it's too small, the V I want could
arc the distance and commit coil suicide. My only other wish is not using miles of wire to get
there. You guys talk like there's only one way, when it appears that at least one chinese
company has already found another. Just because there are gaps in my knowledge doesn't
make me a total rube.

On the idea of saturating cores and otherwise, has anyone ever considered adding less
iron powder and more dielectric powder to the core, to lower the inductance between iron and
air? Seems like the dielectric/iron mix of a core is infinitely variable.

Teslla coil = primary resonant tank driving a power-factor corrected series resonant tank.
That's great and I'm not agin' it, but I don't need a copper monstrosity under my hood,
visual stage effects isn't my goal, thanks.

ragnar

Thu Oct 04 2007, 11:42PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

300kV and you don't think it's big?

How far could 300kV arc? So how big would the contraption have to be, in order for the input not to simply arc across in air?

Why not tell us why you specifically want ignition coils, or what exactly you're trying to do, please?

Shaun

Fri Oct 05 2007, 04:15AM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

We aren't telling you that the ONLY way to get 100kV plus is to build a Tesla Coil. We are telling you the only EASY, REASONABLE (in terms of price, size, weight, power, and performance) way to get 100kV+ is to build a Tesla Coil. Sure, you can get an autotransformer or whatever from some Chinese company. I'm sure it would work great, too. Your first problem with that is, it will be big. And heavy. And you will have to have it shipped FROM CHINA!!! Can you imagine what the shipping alone would be? It would absolutely cost way more than building a TC.

You seem to strongly dislike the idea of winding 'miles' of wire. Let me tell you that winding the secondary is probably the EASIEST part of building a TC, even if you do it by hand. To save time, use a lathe. Don't have access to one? Get an old fan motor or something and attach a longer shaft. It's not a big deal. In fact, an HF coil can sometimes use only a few hundred feet of wire or less. The longest time I ever took to wind something was 3.5 hours winding 32 gauge wire onto 18" of 4" PVC by hand.

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