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Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
would theese:
be suitable to protect a 450v, 5500uf capacitor in a coilgun? I was thinking of getting several and putting in parrallel to increase max curent, would that work?
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
With only 30A peak current each you might need quite a few in parallel, look for something bigger. Really it depends on how damped your circuit is, if designed for it you can get away without any diodes at all! Put the values of your coil gun into Barry's RLC simulator, the negative current will give you an idea of how much reverse current the diodes will need to handle.
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
How can i figure out a approximate peak current? i know it depends on resistance, and inductance, but say the coil was 1ohm, what would be a safe assumption.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
A very safe assumption would be 450 / 1 = 450 A
But with a huge resistance like one ohm you may find that it is so well damped that there will be no significant back EMF at all. You got the link to the simulator, play with it and see what it says.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
hmmm, didnt think 1 ohm was alot.
It all depends, you have not given any details about your design. Your pulse is likely to be long and if your target speed is 50 m/s you might need a coil that is 50 cm long to avoid the projectile being sucked back and exit the coil in the wrong direction.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
sweet, so if i understand correctly, those can stand 200 A reverse each, and 3 amp forward constant. Whats the forward peak current?
If it conducted both ways it would be a wire and not a diode.
The 200A is forward peak current for one "cycle" worth of time, there is a nice table in the datasheet that shows current vs cycles. If you assume that one cycle is 16.7 ms then you should normally be fine.
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diode cap protection
