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[moved] 24,000j Capacitor Bank (Now Complete)

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LarsE

Fri Dec 28 2007, 01:21AM

Registered Member #153 Joined: Sun Feb 12 2006, 03:44PM
Location: Sweden
Posts: 31

Nice bank you got there, i am also curious in what you are planing to use as switch.
Someday i have to finish my 28,8Kj bank so i can try my ETG.

1198804850 153 FT32933 Bank Med Motstand Stor

FastMHz

Thu Jan 03 2008, 08:55PM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

Iâ€™ve found and ordered two identical 1200w MOTs for charging the bank. I have diodes already, and will construct the charging system soon. Iâ€™ve also been asking around about discharge systems for such a huge amount of energy, and have settled on an open-air thyratron, aka triggered spark gap using a high voltage plasma. Essentially, a gap is created and a high voltage lightning bolt is created between the gap thus closing the circuit to discharge the bank. I have the remote control unit already for activating the discharge. It now appears that I have almost all the major components!!!

Jasonr

Fri Jan 04 2008, 12:11AM

Registered Member #167 Joined: Mon Feb 13 2006, 06:41PM
Location: Waterloo, WI
Posts: 54

Well that would work if you don't mind wasting almost all your energy in the spark gap? If it were me I would not go that route.

I know it is way cheaper and easy. but if I could not afford the scrs required I would at least build a solenoid controlled knife switch or push to large copper plates together. Some kind of mechanical contact would be far more efficient.

Jason

Shaun

Fri Jan 04 2008, 03:31AM

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

I wonder how long ANY type of metal-metal mechanical switch would stand up to repeated shots at 24kJ? Unless you could close the switch extremely fast due to the very short pulse width, it would end up as essentially a spark gap anyway.

...

Fri Jan 04 2008, 04:43AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I would take a look at TDU's switch,

FastMHz

Fri Jan 04 2008, 05:35PM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

Thanks for the feedback guys....yeah a spark gap really is my only option...any mechanical contact will weld together or just detonate, and any SCR big enough to handle it will cost more than a shiny new car....I've been researching triggered gaps, and properly designed ones can indeed transfer most of the energy successfully, and have rapid "switch-on" times as well. If they weren't that useful, high energy research labs wouldn't use them to switch mega-amps of current. I'm all for alternative affordable switching methods, of course

FastMHz

Wed Jan 09 2008, 02:36AM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

PROBLEM: I experienced an unexplained diode failure today. I strung 4 1600v 40a diodes together to form a 6400v block...I took my two identical MOTs and stacked them in inverted phase fashion. Next I hooked them up with the diodes to a meter to test the RMS charge potential for my cap bank....and the entire string blew at about 4500 volts.....why would this happen?

Shaun

Wed Jan 09 2008, 03:30AM

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

Were the MOTs in series? At 4400 volts RMS that gives 6.2kV peak, way too close to your strings rating.

If there's no load on the MOTs either, why not just use some cheap 1n4007s in series to test charging DC voltage?

It has to suck to lose those nice diodes, though. I would be very pissed...

FastMHz

Wed Jan 09 2008, 03:56AM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

Yes, the MOTs were in series, and on a variac....I didn't have the variac all the way up, and the meter was only reading 4500v when the string blew...that's why I'm confused...and yes, POed too!

Electroholic

Wed Jan 09 2008, 04:21AM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

why use 40A silicons when a string of cheap 4007(1A) or 5408(3A) would do the job? you can also look at Conner's mot voltage doubler, robust enough to use in a TC. IIRC he used caps and resistors in parallel with the diodes in the string to balance the voltage a little better.

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