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Need 30 kilovolts!

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LAN_403

Oneironaut

Wed May 16 2012, 02:40AM

Registered Member #3616 Joined: Fri Jan 14 2011, 08:47PM
Location:
Posts: 34

In a new project I am doing, I find myself needing a 30kv or better power supply. Endless surplus searching has revealed nothing, but I do have a good supply of pole transformers at the local scrap yard. From my understanding, there would all connect to 14.440kv and step down to 240 volts? If this is the case, I should be able to connect the center tap to 240 volts and have the transformer output 28kv then.

Does this sound feasible?

Brad

genious 7

Wed May 16 2012, 02:51AM

Registered Member #2887 Joined: Sat May 29 2010, 11:10PM
Location: Panama City, Panama
Posts: 107

What kind of amperage do you need?

Oneironaut

Wed May 16 2012, 02:56AM

Registered Member #3616 Joined: Fri Jan 14 2011, 08:47PM
Location:
Posts: 34

Not much really. I am going to charge a large capacitor bank, and am willing to simply wait longer.

I had a 30kv polepig last time, but had to toss it as it was too large to take when I moved. Wish I still had it.

Brad

LuceÅ¡

Wed May 16 2012, 03:14AM

Registered Member #4108 Joined: Sun Sept 25 2011, 11:43PM
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Posts: 149

Why Not use a zvs flyback driver?

teravolt

Wed May 16 2012, 03:51AM

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

how much capacitance and what kind of capacitor are you charging? how many joules. if your cap is big a 240 to 14.440k into a full wave dublier would work. If your bank is small and portable a zvs ie flyback circuit might be more practical

Mattski

Wed May 16 2012, 05:55AM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

If you want something that you can just buy then Information Unlimited has some, no idea what the quality is.

You shouldn't apply 240 across one output to the center tap of a pole transformer, that'll probably saturate the core, it's only designed for half that many volts per turn.

Dr. Slack

Wed May 16 2012, 07:11AM

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

Oneironaut wrote ...

... From my understanding, there would all connect to 14.440kv and step down to 240 volts? If this is the case, I should be able to connect the center tap to 240 volts and have the transformer output 28kv then.

Does this sound feasible?

If by center tap you mean the winding normally outputting 120v in step-down duty then NO, it is not feasible. You can abuse transformers and get away with it with over-current and over-power, but you cannot do that for over-voltage.

You can connect the 240v output winding to your 240v supply, and get 14kV on the HV winding. If your final output is destined to be DC, then rectify with a voltage doubler instead of a bridge. If you want AC, tough.

Oneironaut

Wed May 16 2012, 02:16PM

Registered Member #3616 Joined: Fri Jan 14 2011, 08:47PM
Location:
Posts: 34

Thanks for the input.

I think a flyback may be too small for my project. When I used the pole pig here, I had connected the 120v winding to 120v AC to charge my caps, but this transformer was an oddity, rated at almost 40kv...

http://lucidscience.com/gal-rock%20disaggregator-18.aspx

Yes, I need DC, and last time used a string of 16 HV diodes. There are a dozen pole pigs sitting at the local scrapyard, and the transformers inside the can are larger than the one I used shown here and have dual windings on the core. The plates have been removed though, so I have no idea what they are rated for.

Worst case scenario would probably be 14kv, I guess.

I ballasted my last pole pig using 4 stove elements in parallel, and that worked fine for the ~5 minutes I needed it outputting HV. I know it would be suboptimal to pump 240 into the 120 winding, but for intermittent capacitor charging duty, it seems doable in theory.

Another idea would be to acquire 2 of the pole transformers and run their 240 sides in parallel, tying the 14kv outputs in series to obtain 28kv. I have done this with MOTs, so I know that works, but that's a lot of weight on my wooden shop floor!

I guess trying it will reveal the answer - it always does, one way or the other.

Brad

teravolt

Wed May 16 2012, 04:20PM

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

if you take them out of the oil and its can it may not hold off the voltage any more

Erlend^SE

Wed May 16 2012, 04:34PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

a CW-multiplier circuit driven off a MOT may do the trick?

(I assume you already know the dangers of doing it)

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