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Registered Member #118
Joined: Fri Feb 10 2006, 05:35AM
Location: Woodridge, Illinois, USA
Posts: 72
For high current/high Coulomb, low duty cycle spark gaps, brass actually works almost as well as copper-tungsten or tungsten, and is much cheaper and easier to fabricate. If you ultimately plan to discharge 2 kJ through the gap, you may need to beef up the electrodes AND the plastic housing to provide additional strength and more clearance around the gap for the expanding/ejected plasma. Remember to consider Lorentz forces, especially if your main gap and mounting rods form a partial loop, and also consider the shock wave created when the gap fires. I've seen 1/2" Plexiglas plate shatter on a 4" diameter trigatron when switching ~7500 Joules. Lexan or HDPE may be a better choice for your gap than the thin box you presently have.
Also, if your capacitor bank voltage is only 1 kV, you'll need to reduce interelectrode spacing considerably from that shown in your pictures. BTW, after using a trigatron for several years at power levels between 2500 - 6300 joules, I migrated to a simpler solenoid driven gap. The result was significantly lower maintenance, much wider range of operating voltage, less self-triggering (at higer voltages) or firing failures (at lower voltages. I've never looked back since...
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042
Bert wrote ...
For high current/high Coulomb, low duty cycle spark gaps, brass actually works almost as well as copper-tungsten or tungsten, and is much cheaper and easier to fabricate. If you ultimately plan to discharge 2 kJ through the gap, you may need to beef up the electrodes AND the plastic housing to provide additional strength and more clearance around the gap for the expanding/ejected plasma. Remember to consider Lorentz forces, especially if your main gap and mounting rods form a partial loop, and also consider the shock wave created when the gap fires. I've seen 1/2" Plexiglas plate shatter on a 4" diameter trigatron when switching ~7500 Joules. Lexan or HDPE may be a better choice for your gap than the thin box you presently have.
Also, if your capacitor bank voltage is only 1 kV, you'll need to reduce interelectrode spacing considerably from that shown in your pictures. BTW, after using a trigatron for several years at power levels between 2500 - 6300 joules, I migrated to a simpler solenoid driven gap. The result was significantly lower maintenance, much wider range of operating voltage, less self-triggering (at higer voltages) or firing failures (at lower voltages. I've never looked back since...
the wider gap is the triggered portion, shorted via the HV pulse... the other, extremely small gap (of which the pictures do not do justice) is what the 1kV would jump... and I might switch to 2kV... also, 2 kJ is only the energy I have now... I am going for a LOT more (only limited by the stock of the seller I buy from, but he won't tell me how many he has... and I have to get them one at a time). as for the Plastic enclosure, I plane to leave it rather open, except when not in use... and I always use Lexan rather than Plexi as for a solenoid triggered gap, that is fine but I personally like the exceptional sound of a spark gap and no moving parts ^_^
Account deactivated by user request on 6/11/2009. Registered Member #1071
Joined: Fri Oct 19 2007, 02:13AM
Location:
Posts: 44
I have a spark gap is pressurized to 40 psi then when the pressure is dropped it breaks down. It isnt particularly accurate in timing obviously because it fires in some ~1 second window as the pressure is dropping, but if you arent syncing it to something else than it doesnt matter.
One thing of concern is that your voltage is extremely low, 1000V, I have never found spark gaps to be particularly reliable below at least a few kV. In terms of energy handling, spark gaps can handle almost arbitrary amounts of energy
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042
a flame method would be troublesome... but after a trip to the local electronics surplus, and seeing some gigantic solenoids... I think I may end up using one of those, but the addition of mechanical parts is always a problem with my work... at least when those mechanical parts are not the primary function... But I may have to, since I am using only 1000V... but I will do a basic test once I have to charger built and determine things from there. but the solenoids have some advantages after some thought: no need for an HV Transformer, or Capacitor Discharge to trigger the gap, I would not need to worry about electrode spacing as long as the solenoid can reach, I have less to worry about control isolation for the trigger, since it is no longer HV... I might actually try both, as I have a few extra bolts lying around and I would likely use the solenoid for another project if it doesn't work out...
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
With relay contacts isn't there usually some 'switch bounce' which might pull an arc after it, and even weld up the contacts?
To get over this problem, I use vacuum relays for switching HV, but none that I have could switch anything more than 30A, and the really big ones cost a fortune.
Account deactivated by user request on 6/11/2009. Registered Member #1071
Joined: Fri Oct 19 2007, 02:13AM
Location:
Posts: 44
these guys make mechanical switches maybe you could build a similar design to how they do it. we use their relays under oil for connecting and disconnecting our 100kV charging supplies to capacitor banks.
Registered Member #1500
Joined: Sat May 24 2008, 04:38PM
Location: Ojai, Ca.
Posts: 44
Hi, I have a 5KV/240uf Maxwell that I want to fire at 5kv. I machined 2 very flat and parallel 2" brass dowels. One is to be screwed into the cap the other is to be suspended from an insultaed, robust steel structure for the business end work.
I considered a triggered gap but then thought a very precise gap set to 5KV would surfice. Once I roll the cap around back I will be ready to test it. Fisrt discharge will be into a large copper sulphate water resistor. Is there a down side to this approach?
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Triggered Spark Gaps...
