harnessing lightning, or not
in [Design]
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From: Greegor on 12 Jun 2010 15:18 What were these Maxwell capacitors originally built for?
From: Archimedes' Lever on 12 Jun 2010 15:26 On Sat, 12 Jun 2010 11:35:18 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Sat, 12 Jun 2010 11:20:05 -0700, Archimedes' Lever ><OneBigLever(a)InfiniteSeries.Org> wrote: > >> >> A knowledgeable man would be able to weigh these principals and discuss >>them, without much mention of math to any great degree at all. > >Hilarious. Engineering is all about the math. > >John Engineering conceptualization, however, is not. Just ask A. Garrett Lisi. http://science.howstuffworks.com/theory-of-everything.htm/printable What he ended up with is as mathematical as it can possibly get, yet how he conceived of it was not. You lose... again.
From: Archimedes' Lever on 12 Jun 2010 15:27 On Sat, 12 Jun 2010 12:18:56 -0700 (PDT), Greegor <greegor47(a)gmail.com> wrote: >What were these Maxwell capacitors originally built for? Probably laser pulsers. There are only a handful of applications for them.
From: Winfield Hill on 12 Jun 2010 16:25 Archimedes' Lever wrote... > > John Larkin wrote: >> >> Archimedes' Lever wrote... >>> >>> My cap would flash over as well, but more would remain stored >>> than in any of the scenarios discussed here thus far. >> >> I doubt that. Show us some numbers. Like Win did. > > If lightning comes down here from a half mile up, it can certainly > span the distance between the nodes of any cap you can name ... I'm not going to write a treatise about it, but that's not right. The entire 100MV or whatever isn't instantly available across any spot along the path; instead it has to follow the rules of physics (and electronics). We can analyze what happens in a small region. First, it has a current waveform that rises rapidly, but not too rapidly, to the peak current. This causes a voltage drop across the local path inductance, V = L dI/dt. I say the current rises not too rapidly, which is good for a carefully-designed setup, but at up to say 20kA/us, it's certainly rapid enough to cause mayhem elsewhere. Say there's a modest 1uH of wiring inductance, oops, that's a 20kV drop, lasting 5us or more, long enough to create a new discharge and a new undesired pathway for the continuing 100kA lightning current. My capacitors have 40nH of inductance, limiting voltage spikes from this part of the pulse to a manageable 800V. Then there's the current charging the capacitance. As calculated, 200uF is enough to limit the net voltage rise to 10kV over the 25 to 50us of 50 to 100kA stroke current. During the event, there's a dV/dt = i/C of up to 500V/us on the capacitor, which again, is well under the Maxwell's rating. It's meant to be discharged in as little as 6.6 us, a shorter time than we're considering here. Under that condition its specified design life is 10,000 cycles. So, no, I don't expect the cap to flash over. Bring it on! -- Thanks, - Win
From: Bert Hickman on 12 Jun 2010 16:29
Greegor wrote: > What were these Maxwell capacitors originally built for? All sorts of high-energy pulsed-power applications. Typically, banks of HV metal-cased energy-discharge capacitors are used to supply 10's to 1000's of kilojoules at 100's of kA - MA levels. Common examples include pulsed magnetizers to charge rare-earth magnets, industrial electromagnetic metal forming (and coin shrinking), laser flash tube pulsers, Pulse Forming Networks (PFN's) for driving klystrons in RF particle accelerators, kicker magnets to redirect the particle beam in the same. Other areas include mundane cable "thumpers" to locate short circuits in underground HV power cables, to reactive armor on tanks to create a pulsed magnetic field to disrupt the supersonic copper metal jet used in armor-piercing weapons, and EM weaponry such as rail guns or electrothermal launchers. Basically wherever you want MW - TW of instantaneous power on tap... Bert -- ******************************************************************** We specialize in UNIQUE items: coins shrunk by ultra-strong magnetic fields, Captured Lightning Lichtenberg figure sculptures, and scarce technical Books. Please visit us at http://www.capturedlightning.com ******************************************************************** |