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Registered Member #1334
Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615
Killa-X wrote ...
As for the charger, anything in mind? Maybe a simple variac + MOT?
Don't forget the safty discharge too...never know.
I have a 200mA step-up xfrmr in there at the moment (230VAC->360VAC) which I drive from my control box (includes a 15A variac).
As for safety discharge, the contactors I'm using have 3 n/o sets and one n/c. The HT charging contactor has its n/c contacts set to connect a 5K 50W resistor across the bank. So, if the power fails or the logic craps out, there will always be a meaty resistor across the bank.
This is also the reason I use an analogue meter which is always connected across the bank - even if the power fails, you can still see what's waiting there to bite you... (though it should slowly roll off over a couple of minutes due the resistor mentioned above).
PS. When I fired it at 300V this evening, it shattered my nice acrylic frame for the launch pad and the disc went ricocheting around my workshop
Registered Member #2909
Joined: Wed Jun 09 2010, 12:31AM
Location: fort belvoir, Va USA ( south of DC)
Posts: 145
well i have 16 4700mfd 400v caps that built a 800v bank with, but i never got results like that even with a short wire(thin wire that burns out to shorten the pulse) i only got up to 20-30ft
Registered Member #1334
Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615
pauleddy wrote ...
well i have 16 4700mfd 400v caps that built a 800v bank with, but i never got results like that even with a short wire(thin wire that burns out to shorten the pulse) i only got up to 20-30ft
PS how do you calc ESR?
Top post updated with more photos.
ESR is calculated from the PEH169 datasheet which quotes 17milliohms ESR for each of these caps, and there are 4 in parallel. They are very expensive pulse-rated & long life. The PEH200s I have are listed by Farnell at GBP 91 each (Farnell p/n 1679494) and by RS at much the same (RS p/n 311-1254). Only about USD 90 though from Digikey I have put 169s in there at the moment as I have an awful lot of them, but they are very similar to the 200s...
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
Niiice. You should sometime hook some series too for higher voltage, so you can do some elecrothermal gun shooting possibly =) I got one coming eventually, Just waiting to buy my lathe in a few months.
Hope your stuff goes well, I know people with RIFCA capacitors, those things rock =D
Registered Member #1334
Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615
Killa-X wrote ...
Niiice. You should sometime hook some series too for higher voltage, so you can do some elecrothermal gun shooting possibly =) I got one coming eventually, Just waiting to buy my lathe in a few months.
Hope your stuff goes well, I know people with RIFCA capacitors, those things rock =D
Top post updated with schematic as used at Cambridge Teslathon. Happily launched disc platters round the room with considerable force as they pinged off the ceiling etc.! Never went over about 1200J as the launch pad ripped itself apart and the discs were distorting heavily - need to re-do that and embed it in epoxy.
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Capacitor bank/can crusher...
I have put 169s in there at the moment as I have an awful lot of them, but they are very similar to the 200s...