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Registered Member #659
Joined: Fri Apr 20 2007, 09:14AM
Location: SW Hertfordshire, UK
Posts: 75
guitardude012 wrote ... I will be thinking more about this idea today. If I understand correctly you want to reach a target current as quickly as possible and maintain it?
Exactly, and that current will ideally relate to a flux density similar to the saturation of the projectile. It maybe a complication, but I was wondering about efficiency, not just of electrical energy, but number of stages for a given output, and also, ultimately, the potential for greater velocities in a reluctance configuration.
I think the idea has the potential to go somewhere, although I'm a little too disorganised at the moment to give it too much thought.
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
this would be a perfect adition to my project, could i use the idea? I have ~20 2000v .33uf caps, but i dont have an SCR capable of that voltage, my SCR limit is 1.2kv. I could try 1kv, but i think that would be too low. I was also going to do V-switch.
How exactly would you mesure the current to trigger the SCR? The only thing i can think of is a rogowski coil.
Registered Member #968
Joined: Fri Aug 24 2007, 04:54PM
Location: Norman, Oklahoma
Posts: 104
rp181 wrote ...
this would be a perfect adition to my sci fair project, could i use the idea? I have ~20 2000v .33uf caps, but i dont have an SCR capable of that voltage, my SCR limit is 1.2kv. I could try 1kv, but i think that would be too low. I was also going to do V-switch.
How exactly would you mesure the current to trigger the SCR? The only thing i can think of is a rogowski coil.
Not sure how you would read current that fast.
I would try using some differential equations magic to solve an equation with dv/dt so that you can base it off voltage.
V switching with .33uF caps at 1kv is going to suck I think, though EV managed it with 800V. The final SCR(or SCR bank) is going to have to be a beast to handle the voltage spike you will get from being under damped. What are their turn-off times? I need more time and money to test some TVRs I got that should be ideal for this job.
What peak and target currents(that you are trying to maintain) are you planning for at the moment? Inductance?
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
well i can't do it, aparently both of the SCR's died, so i only have one left. The one left for some reason has extremly high leakege in the off state. The SCR triggeres fine, but when its not triggered it leaks and gets warm. I can't even charge my caps past 100v with my 300v capable supply.
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General coilgun thoughts
