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Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Hey guys, i just whipped this up:
It documents the latest DRSSTC i made. Whats special about this is that it survives letting the coil arc back to itself, because the electronics are properly grounded and coupled where necessary. The webpage explains it pretty well i think, so have a read if you are interested in DRSSTCs and keeping them reliably running.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hey, that is beautiful work Steve. ''strike ring had been sabotaged''
Plexiglass construction is pretty, but are you sure it is rigid enough? I mean, it just looks like it would shatter into pieces if accidentaly dropped from 50cm or so. I had somewhat bad experiences with 5mm plexi as support material. Now I use welded steel :O
Weird idea to use a common mode filter on the GDT. Maybe some TVS to ground after the filter would be good as well? (probably more use than those gate TVS's).
I see you still use isotop 40N60's... where do you get them, or is this your remaining stash?
I have been looking for a while for suitable and not too expensive replacement, and found these:
what do you think? They are even cheaper for similar rating but 30 pieces minimum buy, so only a group buy I guess. I myself am stuck with thermal management for non isolated TO247 packages and like..
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Weird idea to use a common mode filter on the GDT. Maybe some TVS to ground after the filter would be good as well? (probably more use than those gate TVS's).
Nah, i dont think you understand the problem exactly. Sure, the primary of the GDTs voltage will raise in common mode noise briefly, but i dont care, it doesnt matter.
I see you still use isotop 40N60's... where do you get them, or is this your remaining stash?
Remaining stash.
I have been looking for a while for suitable and not too expensive replacement, and found these:
what do you think? They are even cheaper for similar rating but 30 pieces minimum buy, so only a group buy I guess. I myself am stuck with thermal management for non isolated TO247 packages and like..
Those things look sweet! Even lower Rth(j-c) than the 40N60s from fairchild.
Is there a whole lot of interest in a bulk buy? I could afford $400 in IGBTs right now provided i reclaim most of it. I dont really even need any of these things, but i still like to have stuff like this around for when i decide i do need it .
Registered Member #618
Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628
Nice work agian steve. I have some thoughts for you
1) Fairchild still makes and sells 40n60s from their site, nevermind I thought I had seen 40n60 isotop minibrick igbts while looking for igbts for my mini drsstc.
2) If you were to choose, which driver would you say is more stable/reliabe, your drsstc3 or your new discrete driver?
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
2) If you were to choose, which driver would you say is more stable/reliabe, your drsstc3 or your new discrete driver?
Either one, they are basically the same control electronics board. I like the newer gate driver because it doesnt require a step-up GDT, but the trade off is about an extra 25nS of total delay, not a big deal at <200khz, but might be annoying at higher frequencies.
Thanks for the tips Chris! I'll have to try and avoid dropping this thing from any significant height :P.
Registered Member #1107
Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792
I don't know why but i still feel worried about hooking the rf ground to the mains ground. can it be hooked up so the lv electronics connect to the mains ground, and the secondary and h bridge connected to a rf ground and still have primary strikes ok? Also what kind of interrupter did you use?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I knew my way of building DRSSTCs would catch on in the end Steve used to tease me for under-running 40N60s and shielding heck out of everything, and now he's promoting it like he thought of it.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
I knew my way of building DRSSTCs would catch on in the end Steve used to tease me for under-running 40N60s and shielding heck out of everything, and now he's promoting it like he thought of it.
Haha! Its so true. To be honest, im limited by my tank capacitor voltage rating right now, rather than babying the IGBTs. Ive done nasty things to this thing so far like running with out a breakout point, requiring i manually ignite the arcs. I have kicked the input voltage up some, to 140VAC, but eventually i do want to have it going on 210VAC from my variac. I still believe we should keep these things running with Vbus at half of the Vce breakdown rating. Im gonna have to use more than 2 MMC caps to get to this point... probably umm 6 or 8.
I guess more recently ive realized the slop in my old designs, so im trying to rectify that. As a "real" engineer now, some of the stuff i did in the past seems unacceptable and unfinished, so im making some attempts to make sure the hobbyists here can enjoy reliably running coils.
I don't know why but i still feel worried about hooking the rf ground to the mains ground. can it be hooked up so the lv electronics connect to the mains ground, and the secondary and h bridge connected to a rf ground and still have primary strikes ok? Also what kind of interrupter did you use?
Yes, it bothers me a bit too for big coils. I think what might be the solution is a filter on the mains ground lead to keep the tesla coil junk out of the mains wiring, but still provide a 60hz ground for safety. I do not suggest running the LV electronics on a different ground than the heatsink, that could put excessive stresses on the GDT because these 2 grounds may well be quite different!
The interrupter is one of my micro-controller based ones, but it was just running as a plain old timer when testing this coil. Its mainly impressive for the MIDI control. I use a fiber optic link exclusively now, and recommend it. It costs more money, but i really enjoy the isolation especially as the coils get bigger and bigger.
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New DRSSTC, secondary to primary arcing is OK!
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