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Rebuilt Cap Bank - Now with a 200 Pound Pulse Discharge Cap

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Neil

Sun Dec 07 2008, 01:45PM

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

After my last capacitor bank blew up, I decided to purchase a large pulse capacitor from General Atomics Energy Products in the USA and import it to Australia. The capacitor is rated at 11,000 volts, 525 uF however measured 530 uF and can discharge up to 125,000 Amps.

It finally arrived on Friday last week. I was very excited

I stayed up until 1 am Friday night working on it and got up at 6am the next day to keep going with it, by 4pm I had it ready to test fire.

Blown up cap from last bank

New capacitor all fitted

Front of the bank

Controller with digital readout

Capacitor label

The capacitor is rated at 11,000 Volts but intend not to take it much past 5,000 Volts. The reason for this is the rated life of the cap being 3000 discharges. Because the life of a capacitor is logarithmically related to voltage reversal, charge voltage etc, by reducing the charge voltage by half it can greatly extend the cap life and allow more reversal. The below table shows the relationship between voltage derating and reversal allowed based on the original rating for the capacitor.

1228655617 1458 FT0 Voltage Derating Vs Reversal

To help me monitor my voltage reversal and extend the capacitor's life, I have also purchased a Rogowski coil from a company called Powertek in England, through a company here who are an agent for them. It has an integrator which outputs +-6 volts relative to the coils rating, mine is rated at 120kA so for example at 3 volts it will be 60kA and I can view this on my oscilloscope. A product range for these can be found here http://www.powertekuk.com/cwt.htm I have to wait until mid January for this to arrive. These were not cheap, to buy them here it was roughly $3,000

Here is the first test fire of the new bank------->>>>>Youtube - Test Fire<<<<<---------

I decided until I get my Rogowski coil I would play it safe and just blow up wires rather then trying for can crushing with coils of wire ect. I used about a foot long piece of copper wire and charged the bank to 3,000 volts, about 2385 Joules. The wire completely vapourised

There wasnt a piece to be found. There was still 1000 volt left in the cap. I was very pleased.

I will post more videos and pictures once I play around more with it. I plan to do can crushing, build a rail gun and launch objects with it, but I have to work and study for a university degree so in time I will get there.

aonomus

Sun Dec 07 2008, 03:19PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Nice cap. Good that you finally got a new cap, celebrate with can crushing (make sure you have some kind of shield for the work-coil).... with that cap you could probably make a really nasty coin shrinker too....

rp181

Sun Dec 07 2008, 04:54PM

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

Very nice construction.
I think It would be worth it to take it to 11kV (32kJ vs. 6kJ!) once in awhile. What is the intented purpose? The only thing That i can think of is a railgun. You would be able to make a very nice one with your resources.
You should consider a pulse discharge SCR assembly. (If you consider it, check out FMCC group, there based in europe.)
Do you plan to use thicker wires?
How long does it take to charge?

Backyard Skunkworks

Sun Dec 07 2008, 08:00PM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

That is the biggest capacitor I've ever seen...

El_Roberto

Mon Dec 08 2008, 01:58AM

Registered Member #1774 Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135

Thats strange I posted in this thread last night and today my post is gone! Anyway awesome cap, cant wait to see more of it in the future and I hope you charge it up to 11Kv for a railgun. Wish I could afford one myself because I know how much they cost, How much did you have to pay to get that beast imported?

rp181

Mon Dec 08 2008, 02:05AM

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

He posted in another thread:
It was $9,913 USD which was about $12,000 AUD for me with the exchange rate at the time. If you buy 4 or more, this price just about halves. Unfortunately for me, it was another $3,800 AUD to import it and pay frieght, tax etc on it so I just bought one. They seem very easy to deal with and I had no problems importing it for anyone else considering something like that.

El_Roberto

Mon Dec 08 2008, 04:22AM

Registered Member #1774 Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135

Well I know the first thing im going to do when I win lotto... I knew how much it cost for the capacitor but I didnt think it would cost any where near that much to get it imported

Neil

Mon Dec 08 2008, 10:08AM

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

rp181 wrote ...

Very nice construction.
I think It would be worth it to take it to 11kV (32kJ vs. 6kJ!) once in awhile. What is the intented purpose? The only thing That i can think of is a railgun. You would be able to make a very nice one with your resources.
You should consider a pulse discharge SCR assembly. (If you consider it, check out FMCC group, there based in europe.)
Do you plan to use thicker wires?
How long does it take to charge?

Thanks. Trust me, thats such a very tempting thing to do, to have 32 kJ of possible storage sitting there is just teasing me

, but after blowing up the last lot of caps, I remember how disapointing that feeling was

.

I had a look at that FMCC group...WOW. How cool would that be to have one of those, but...I bet their prices would be hard to distinguish between phone numbers. I've already spent enough on this so far lol.

I will start to use larger wires next time I play with it, I really only had the time for one test fire after spending the time to get it back going. I keep it on the farm I used to live on and by the time I had tried it out I had to drive back to where I live now about an hr and a half away. Farms are good though, no neighbours to disturb with large bangs.

To get to the 3,000 volts, took maybe a minute or so but was not turning the variac very quick, just slow and steady until I know its all good.

rp181

Mon Dec 08 2008, 01:32PM

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

I think this is different then the other bank. Your other capacitor's didn't even look pulse rated, and these are pulse rated and come from a company with a excellent reputation (There the ones who made the navy railgun bank!). Usually its recommended to have a 10% safety factor.

El_Roberto

Mon Dec 08 2008, 08:24PM

Registered Member #1774 Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135

Shouldnt it have some sort of warranty? I mean with how much you paid for it, and it is a pulse discharge cap so if you destroyed it doing just that then they should replace it for you.

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