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teravolt

Sun Oct 04 2009, 11:41PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

maby you could use some big inductors or capacitors in series for balast on that beast

Neil

Mon Oct 05 2009, 12:10AM

Registered Member #1458 Joined: Wed Apr 30 2008, 09:47AM
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Posts: 51

Steve McConner wrote ...

Dr. Kilovolt wrote ...

These things have really low impedance

Yep, it says right on the rating plate, "Impedance 4.3%". That means the unballasted short-circuit current would be about 25 times the rated current.

I had been trying to work out just what that meant, thanks for the info!!

rp181 wrote ...

May I ask how much this cost you, and how much you are planning for the whole project?

Sure. It was AUD$1650 for the transformer and AUD$698.5 to get it transported over from Perth in Western Australia. I was actually really suprised with the price, its used but I thought they would have cost way more, and to also have had it reconditioned, painted, tested etc I couldn't be more happier with it. The company I bought it off were also excellant to deal with. I would have spent a lot more on one actually, my main problem in the past here was just trying to find someone that would actually sell me one, had tried power supply companies many times and they just dont seem to like selling to the public especially after they know what you want it for.

I havn't really set a target $$$ figure to stay under, I have always wanted a large coil so I'm just going to build it. I've always thought with this stuff that anything I spend is really an investment in my education. Well thats what I try and tell myself anyways when I add up the price of the individual peices and realise the total

haha

rp181

Mon Oct 05 2009, 12:29AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529

:-O

You really do go all out. I hope you didn't just toss the pulse capacitor aside :)

Couldn't you use the pulse capacitor for the TC cap?

GeordieBoy

Mon Oct 05 2009, 12:34PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

If it was me, i'd run it with 230/240V in and take the full 22kV out, instead of designing for 11kV.

If you're making everything else to fit the transformer then i'd design for this higher impedance because efficiency will be better. Peak capacitor voltage will be around 45kV so i'd design the capacitor for at least 50kV.

You will certainly need to ballast it, because the s/c current will be huge as Steve Conner pointed out. The best method I found was to get a laminated E-I core set and wind a simple ballast like this:

You can easily get 40:1 adjustment range on the current just by altering the air-gap. I wouldn't go for a resistive ballast - You will get appauling performance and waste most of the input power as heat.

Although you only want to run at 5000 watts to start with that transformer wound be good for short runs at 20 or 30kVA so there's plenty of room for expansion. Another reason why designing for the higher voltage would be better in the long run.

-Richie,

Hazmatt_(The Underdog)

Tue Oct 06 2009, 08:57AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

If it were me, i'd be a little more conservative at 15KV, that way my peaks would be around 30-35KV, just shy of the 40KVDC peak rating of the more widely available doorknob capacitors.

Guess I better lock up my box then huh! 016f

Neil

Tue Oct 13 2009, 09:09AM

Registered Member #1458 Joined: Wed Apr 30 2008, 09:47AM
Location:
Posts: 51

I decided to price a professionally built inductor for the current limiting of my pole tranformer. I have bought off a company called Torema here in Australia before and decided to enquire there again as they had good service. I asked them to design what I needed so my short circuit current through it would be 23 amps to match my Variac rating. They came back to me with a 33mH inductor, a toroid coil, measuring diameter 220mm by 105mm high. In reading up of toroid coils, I've seen written that they can be more efficient than what EI designs are. Has anyone had experience with toroids before? good/bad? Price quoted is $870.31

rp181

Tue Oct 13 2009, 12:10PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

With the EI core, you can adjust the current it passes by changing the airgap, eg. more flexible and more uses for your money.

Dr. Dark Current

Tue Oct 13 2009, 03:23PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Neil wrote ...

In reading up of toroid coils, I've seen written that they can be more efficient than what EI designs are. Has anyone had experience with toroids before? good/bad? Price quoted is $870.31

o_0
you can probably make one yourself for 1/10 the price, plus you get that "I built it myself" feel

and I think the inductor does not need to be rated continuously, because 1) a TC does not draw short-circuit current, 2) I doubt you'll be running your coil continuously over half an hour

(these big transformers/chokes take >3h to reach their working temperature...)

GeordieBoy

Thu Oct 15 2009, 01:58PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

I@m not sure how you would incorporate the magnetic gap into a toroidal design, unless they are using some powder material with a distributed airgap.

As Dr kV said, you can easily make this yourself using an E-I laminated iron core set.

I got mine professionally made because I was short of time when I needed them and had spare cash, but they were expensive. If you make it yourself, you can design it exactly how you want it. And you can change that design as and when you want to. You can be sure that you@ll want to change the ballast inductance value when you start experimenting with different tank capacitor sizes, power through-put levels, or rotary bps rates. So, I@d definitely go with a variable gap design to allow this adjustment to be made easily.

-Richie,

Gunboat

Thu Oct 15 2009, 02:41PM

Registered Member #338 Joined: Thu Mar 23 2006, 12:28PM
Location:
Posts: 41

I did a google search one time and this guy in Oklahoma had built a "Big Tesla Coil" with a video. Looks like he didn't spend all that much to make the coild itself,but he did have the pole pig and a pulse cap...was an awsome video...

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