Busbar material / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

Busbar material

first previous 3 4 5 6

Move Thread

LAN_403

Forty

Mon Jul 18 2011, 06:33PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

well don't do the wedge thing then. use your piston to slam a plate down on to another plate. or make a triggered spark gap. best bet would probably be a puck scr though

klugesmith

Mon Jul 18 2011, 07:56PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Don't be too quick to blame the switch. What percent efficiency were you expecting, and why? Suppose the coil design is far out of tune for such a large capacitance? The pulse duration (including the electrical load of coupled projectile) should match the time the projectile moves, but doesn't move too far. Chart your launch height vs. charge voltage, and see if it's more or less efficient at lower energies (where the circuit time constants are the same, but the projectile does not leave as fast).

You might also try launching a much thicker and heavier piece of aluminum or copper, using the same coil.
Perhaps a 1/2 inch stack of HDD platters taped together!
Does the pancake coil have a firm backing, like a concrete slab or block?

One way to take the pneumatic switch out of the picture is to just touch the wire ends together, using an insulating handle with eye & ear protection.
Before you specify a puck SCR: what peak current and pulse duration do you expect, and why?

[edit] p.s.
1. Nice work with the switch assembly!
2. Note, 700V is pretty low to make a triggered spark gap work in air at ordinary pressure.
3. If a large fraction of 3 kJ were dissipated in the switch spark, which I doubt, the blast would be almost like that of an M-80. How hot are your coil and interconnect wires, immediately after a shot?

haxor5354

Mon Jul 18 2011, 08:23PM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

for the switch, try slamming a hammer into an anvil.... it might just work
UPDATE: seems like you need a krytron for this job

also is it possible to make an EMP with your large capacitor bank?

klugesmith

Tue Jul 19 2011, 12:03AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

haxor5354 wrote ...
for the switch, try slamming a hammer into an anvil.... it might just work
UPDATE: seems like you need a krytron for this job

I like the hammer and anvil idea.

But krytrons are not the tool for this job. Their leads (perhaps 26 or 28 AWG) would be exploded by Grenadier's current pulse. Krytrons are made to switch higher voltages, lower currents, much shorter pulses (and much less energy), and much faster risetimes.

Here's one of mine running in glow-lamp mode.

Firing sets for exploding bridgewire detonators have C on the order of 1 uF, charged to V on the order of a couple kV, with stored energy in single-digit joules.

haxor5354

Tue Jul 19 2011, 12:24AM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

i thought they could handle several kilo-amps

pauleddy

Tue Jul 19 2011, 12:44AM

Registered Member #2909 Joined: Wed Jun 09 2010, 12:31AM
Location: fort belvoir, Va USA ( south of DC)
Posts: 145

if you want to make the disk go higher shorten the pulse, your bank is simular to the one i made, put a short piece of telephone wire (like 1cm) in series with your lanch coil. it will it will shorten the pulse plus make a big bang. i nearly double the hight of my plattes by doing that, and if you dont want the bang put the break unde a tank of water it makes it quiter

klugesmith

Tue Jul 19 2011, 01:12AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

haxor5354 wrote ...
i thought they could handle several kilo-amps

Yes, for 10 microseconds, time after time.
Like gas tube surge arresters in packages that look like neon glow lamps:

I don't know if electrolytic banks can be discharged in much less than a millisecond. For one capacitor, what time is C * ESR, or sqrt( C * ESL ) ?

[edit] Re. Paul's suggestion:
I think another way to shorten the pulse is to make the coil with fewer turns of thicker wire.
Or make several interleaved spirals, then they can be connected in various series/parallel combinations to change the timing:

teravolt

Wed Jul 20 2011, 01:16AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

Grenadier, do you have a picture of your load and setup? i am having problems opening your link

perhaps your load coil is to small or wrong inductance. I don't think it is your switch. do you have a data sheet link or picture of a cap. perhaps the ESR is high in those electrolytics

Sulaiman

Wed Jul 20 2011, 06:15PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

I think that electrolytics are not the best choice for a ring launcher,
high voltage non-polarised (e.g. polypropylene) capacitors
would 'ring' at a high frequency
(I think it's Nx(dI/dT) that works.
ALSO, the switch would be easier.

first previous 3 4 5 6

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob