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Registered Member #1316
Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365
I have found 2 100 uf 200 volt motor start caps. Has anyone ever heard of using the reverse voltage from the last shot to reverse charge the cap then charging in reverse polarity and swich charging polarity every shot?
Registered Member #1083
Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256
If you can get the switching timed right, it should work. Of course you won't get full reverse charge from the shot. I've actually been thinking about this sort of thing myself, except I was thinking of some sort of magnetic field recycling coil. In a coigun/induction launcher, not all of the energy goes into the projectile. I was thinking like putting some sort of coil on the side of the main coil opposite the projectile; this would be induced with the magnetic field that wasn't induced into the projectile. Of course, then the problem is how to catch that charge on a capacitor and disconnect it before it returns to the coil.
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
You couldn't use a single SCR to trigger anymore, since they only conduct one-way. It would have to use a mechanical switch of some sort. Of course, doing that wouldn't help, it would just let the capacitor ring down.
If you used two SCRs in inverse-parallel, then you could fire one SCR and then when the capacitor reverse-charges, use the other SCR to fire it in the opposite direction. I don't know how SCRs stand up to being reverse-biased like that, but this is just speculation.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
That would depend on the equivalent series resistance of the capacitor. If the ESR is so low that the pulse is very short you need to take the inductance into consideration.
Registered Member #1316
Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365
Ok. but i dont have the parts to build the ESR tester. does anyone have an aproximation? i asked the electronics teacher at my school and he says the caps i am using should have lower ESR then lyiacs.
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Motor start capacitor coilgun
