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Registered Member #952
Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388
I'm building a small wire exploder/energy pulser which will probably be used for coilguns and railguns too. I've got a 300v 480uF cap bank. That makes ~25J.
I would like to know if there are some inexpensive and common SCRs for this kind of application. With wire exploders and RGs the pulse current will be quite high. Should I consider paralleling some of them?
Registered Member #1262
Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451
spark wrote ...
With wire exploders and RGs the pulse current will be quite high.
The current spike is gonna be massive as wire exploding is basically a flat short. TYN640RGs run $1.80 if you buy 10 from mouser and they can take 400A peak @600V, I used these for my coilgun.
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
The capacitor you have probably has an internal resistance of around 300mOhm, so you are looking at currents of less than 1kA. Even a small TO220 SCR should be capable of coping with that, i.e. any basic SCR from a light dimmer or so would do.
Registered Member #1208
Joined: Thu Jan 03 2008, 05:30PM
Location: Chesterland, OH
Posts: 154
I think that'd be less than 300mOhm. more like 100mOhm.
so 3KA i would do it mechanically, just because the close time is shorter. your still looking at 8 mSec, so it may not be spectacular.
make sure you have a bleed resistor, I once had 150 J left in a bank after a pancake coil blew up. I remember poking it with a screwdriver, trying to get it to discharge. unfortunately, I took off my ear protection.
Ramses
p.s.- this should be in the high voltage thread. you aren't accelerating anything with electromagnetism, are you? I
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
"Usually" exploding wires is done with a much higher voltage, so no, SCRs are not used on those. Since I don't think there are any "usual" railguns, I don't have an answer for that question.
For the capacitor bank YOU have at hand however, a SCR is the fastest, safest and best solution.
Registered Member #952
Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388
Thanks. Here's a picture of a wire exploded with that cap bank and a mechanical toggle switch. The switch died just after doing this. The "wire" was one strand of multistrand wire.
As you see, even with this low energy and voltage, wire explodes quite happily
Registered Member #952
Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388
I finished it now
Sorry Uzzors, copied you plexi design I didn't bother to mess with SCRs yet, I kept it simple with just a mechanical key switch. It's very portable and as a coilgun it shoots quite nicely through paper
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Teh Mini Energy Pulser
