SCR energy recovery
uzzors2k, Tue May 15 2007, 07:15PMMy coil gun uses a single SCR for switching, and I was wondering, can I recover the energy in the negative current pulse? The length of the pulse is 3ms. A 555 set up as a monostable with a 0.1 ms on time could be used for triggering. The SCR will turn off once the current reverses, and the clamp diodes will send the energy back to the capacitor, saving some energy. Or so I think, am I right? There's not much energy to retrieve, but there's no point in wasting it.
Re: SCR energy recovery
Madgyver, Tue May 15 2007, 07:38PM
Principaly thats doable. Its just your circut wont work. The diodes wont send back the energy to the caps but will short circuit it.
Madgyver, Tue May 15 2007, 07:38PM
Principaly thats doable. Its just your circut wont work. The diodes wont send back the energy to the caps but will short circuit it.
Re: SCR energy recovery
Steve Ward, Tue May 15 2007, 08:47PM
You need a full-bridge arrangement for energy recovery (or at least, this is the topology that comes to mind). Since you are only interested in switching one direction, and recycling in the other direction, you only need 2 switches and 2 diodes (as opposed to 4 of each). Im pretty sure ive seen some people use this to pulse their coilguns... i think they called it a "V switch" or something like that? I made a small coilgun using this idea, it worked as expected producing a single half-sine pulse (i turned off my switches during the "recycle" period). You will likely see a large decrease in performance vs just dumping the whole cap at once into the coil, this is because you are only going to use a small fraction of the energy in the capacitor before the LC oscillation reverses directions and you cut off the current. So this may require serious re-working of an existing coilgun setup to get satisfactory performance. So what im getting at is, the energy you want to retrieve is likely contributing to accelerating your projectile.
Steve Ward, Tue May 15 2007, 08:47PM
You need a full-bridge arrangement for energy recovery (or at least, this is the topology that comes to mind). Since you are only interested in switching one direction, and recycling in the other direction, you only need 2 switches and 2 diodes (as opposed to 4 of each). Im pretty sure ive seen some people use this to pulse their coilguns... i think they called it a "V switch" or something like that? I made a small coilgun using this idea, it worked as expected producing a single half-sine pulse (i turned off my switches during the "recycle" period). You will likely see a large decrease in performance vs just dumping the whole cap at once into the coil, this is because you are only going to use a small fraction of the energy in the capacitor before the LC oscillation reverses directions and you cut off the current. So this may require serious re-working of an existing coilgun setup to get satisfactory performance. So what im getting at is, the energy you want to retrieve is likely contributing to accelerating your projectile.
Re: SCR energy recovery
uzzors2k, Tue May 15 2007, 08:54PM
Ok, thanks for the tips. In the RLC simulations my current coil gun is pretty overdamped, and the reverse pulse is only 20V high theoretically. So there wouldn't be much energy to receive in the first place.
uzzors2k, Tue May 15 2007, 08:54PM
Ok, thanks for the tips. In the RLC simulations my current coil gun is pretty overdamped, and the reverse pulse is only 20V high theoretically. So there wouldn't be much energy to receive in the first place.
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