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Registered Member #1787
Joined: Thu Oct 30 2008, 12:33AM
Location:
Posts: 13
ok, i've been looking around and can't find the answer. why do most people use scr's or igbt's for switches in their coilguns. why not just use a spst switch? or is it more efficient to use the other switches. i got some scr's just don't see why.
Registered Member #1107
Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792
spst switches are made for small currents and the small contacts will weld together with just a small photoflash cap. Scr's have a high pulse rating and they can take the pulse from the cap bank. a small stud scr usually has around a 800-1000A pulse rating and as discharge time decreases that rating goes up exponentally.
Registered Member #1262
Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451
Very large fast closing switches can work up to a few hundred joules. TCG is right that normal sized switches will just weld, and this welding takes up a lot of the energy that was supposed to be used to move the projectile.
If you can get a switch to close without any major sparking, it will work fine. This is far easier said than done when your dealing with capacitor banks.
yea, if theres sparks then its wasting a lotttt of energy
On my gun, i was getting 0.25% efficiency before my scr arrived (i was just touching the coil wire onto the caps) After i got the scr installed, it increased to around 1.5%, so it makes a big difference
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why not use spst switches on single stage coilguns?
