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Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
How well do mechanical switches work for capacitor banks? My bank is ~1.5kJ. Check my blog (in sig) for a pic. What kind of efficiency can i expect? I still need to find a way to pull back the top plate and attach the cables.
Registered Member #1262
Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451
I think you'll find that spring loading the switch or finding some other way of closing it as fast as possible is the best. In theory, a mechanical switch could be almost as efficient as a solid state switch if it closed fast enough to eliminate (almost) all the plasma. The plasma is caused by the switch arcing over before its fully closed, and a lot of energy is wasted when you get large amounts of switch plasma. If you can get the switch to cover the arc over distance before the circuit current rises too high, the switch will work quite well.
The higher the bank voltage and capacitance, and shorter the pulse, the faster the switch has to close to prevent huge energy losses in the form of plasma, not to mention welded contacts.
If your talking about several hundred volts, 1.5kJ may simply prove too much energy to switch mechanically without high losses. I'd say its worth a try though... if the results arn't any good, just use SCRs.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Remember that you are making a system, you have to tune the different parts of the system to make it work optimally as a whole. A coil with a larger inductance ramps up the current over a longer time and a mechanical switch can be very efficient.
As usual making a coil gun is very simple, making an optimal coil gun is very very hard.
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Mechanical Switch efficiency
