Capacitor exploded, any ideas why? / Electromagnetic Projectile Accelerators / Forums

Forums

4hv.org :: Forums :: Electromagnetic Projectile Accelerators

« Previous topic | Next topic »

Capacitor exploded, any ideas why?

previous 1 2 3 next

Move Thread

LAN_403

Neil

Tue Jul 01 2008, 11:40AM

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

Thanks for the comments they have helped me, I have come to a sad conclusion it is not worth the risk to run on the remaining caps, or risk smashing the more critical areas of my case that would take forever to repair should another one explode. Also given the comments, it seems the caps are not as fit for purspose as they seemed to portray in their descriptions on Ebay.

I have been looking around for more pulse caps and found a site in the USA that sells them,

They call themselves "General Atomics Energy Products" . Has anyone had any dealings with them before or used their capacitors? I tried emailing someone at Aerovox but no reply so far and Maxwells site I dont think even has a listing of their products that I could find.

Anyways, this is the capacitor I am keen on getting. It is rated at 11kV at 525 uF giving it storage of 31.5 kJ. Its rated discharge amps are at 125 kA and is rated for 10% voltage reversal. Ive been given an estimate of $5500 for this line of caps as an average price but they are getting back to me with a quote. Quite a lot of money so will give it some thought, but should I get it, my plans are to run it at 5.5 kV max which is 50 percent of its rating, the reason for this is according to a derating vs voltage reversal graph on their site, I could run as much as 92% voltage reversal at this voltage with this cap and still get the rated life of 30,000 discharges. It will still give me 7940 Joules of storage but with much more peice of mind knowing I am not pushing it to its limits. If i check it with my oscilloscope and am getting much less reversal that 92% than I could up the volts to match.

Does anyone have any comments on how they think this capacitor would go, is it worth the money, will derating really help make it last in practice. Any comments would be appreciated. Thankyou.

Neil.

rp181

Tue Jul 01 2008, 02:20PM

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

Keep in mind those caps have a rated voltage (the one they show) and laso a lower rated voltage in air, your supposed to put it in pressurized gas (or oil) to use the maximum rating, i think this is only for 100KV ones, but make sure. These are also very big, keep that in mind. I tried emailing them too, i didnt get a reply (then again, i was asking for sponsoship of my project)

Tom540

Tue Jul 01 2008, 05:21PM

Banned on 3/17/2009.
Registered Member #487 Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617

I just applied for a job at General Atomics.

Neil

Tue Aug 19 2008, 01:15PM

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

I decided to buy the capacitor I mentioned above from General Atomics, 525 uF at 11,000 volts giving 31.5 kilojoule at full charge at 125,000 amps. Turns out there is a premium to pay for a small order between 1 and 3, ended up being about $10,000 US dollars for the 1 plus shipping to Australia

.

I'm excited though

, I'm really looking forward to getting this, though have to wait 14-16 weeks for them to make it and fly it over. I better not blow this one up at that price...

rp181

Tue Aug 19 2008, 08:42PM

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

wow, you are clearly into the hobby for spending this much on a single capacitor. You shouldv'e bough a couple =)

projects? all i can think of is railgun.

Charging is gonna be hard.....

Firefox

Tue Aug 19 2008, 08:53PM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

It isn't any different than someone spending 10k on a block for his muscle car, entertainment system, or computer. To each his own! I would love to see that cap when you begin experimenting with it. 1.375 Gigawatts!

Fraggle

Wed Aug 20 2008, 04:38PM

Registered Member #1526 Joined: Mon Jun 09 2008, 12:56AM
Location: UK
Posts: 216

You`re going to have to build a serious rig to use that bad boy safely! You`ll be able to do anything on the HV menu with it and I`m jealous. Get winding a big coil for some sheet metal forming!

Shaun

Wed Aug 20 2008, 05:07PM

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

14 to 16 weeks, eh? Darn, looks like you'll just miss Halloween. What better excuse to blow up a 30+lb pumpkin?

Fraggle

Wed Aug 20 2008, 06:05PM

Registered Member #1526 Joined: Mon Jun 09 2008, 12:56AM
Location: UK
Posts: 216

Oh! I just read the full specs and that cap only stands 10% reverse voltage. 100+ kA might be a bit tricky to clamp...

Maybe it`s not too late too change it for one of the 80% ones instead?

edit: Ha! Ignore my rambling I just read your post in detail :D

Seoul_lasers

Thu Aug 21 2008, 05:30AM

Registered Member #1630 Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115

Fraggle wrote ...

Neil, dont overlook microwave oven caps - you could easily achieve that can-crushing result with as few as six and they`re easy to get hold of.

It is VERY unwise to use MOT caps as they will detonate on you often with unexpected and specatular fireworks if you should happen use them for pulse discharge, or can crushing. THEY ARE NOT DESIGNED FOR THAT KIND OF ABUSE!
You should really contact MOT_man about this he'll fill you in on the rest.
I can remember Mot_man's mot cap adventure.

previous 1 2 3 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob