If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #2288
Joined: Wed Aug 12 2009, 10:42PM
Location: Cambridge, MA
Posts: 179
I'm having a very strange problem with a newly built mini DRSSTC. The driver works great, and the coil can make arcs a few inches long at 100V 1A input. Secondary is on 1" PVC, 6" long, 38 gauge. Torroidal topload with a major diameter of about 8". Fres of the whole setup is 535khz.
The thing is, this test making a few inches of arc is with the base of the secondary not grounded, not connected to anything except an arc contact point. The problem comes up in that if I connect the base to earth, negative DC bus, or anything even remotely resembling earth, the coil entirely stops making high voltage. The driver works normally, draws normal bus current, produces primary current waveforms as expected, driver makes normal buzzing sound, it's just there's no arc or high voltage present. Take off the ground on the base, and it immediately works again. It acts the same with or without a breakout point.
Can't keep going without it grounded though, since the base desperately wants ground and will just arc to the primary to get it.
I can't come up with any rational explanation for this, does anyone have experience with a coil that refuses to be grounded?
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
The thing that come to mind for me is that when you ground it you are basically adding capacitance to the secondary circuit throwing it out of tune.
This is the way I think about it, the toroid is one plate in the capacitor and the grounded surrounding area is the other plate with the dielectric being the are air in between. When the coil is not ground the other plat is only the bottom of the secondary and the wire itself, a very small plate indeed. But when you ground it you now has supper sized that other plate throwing the resonant frequency way low! I would suggest retuning after you ground the coil.
Also the fact that your primary is sitting on the grounded surface can't be helping much ether. Raising it up would probably help as well.
May I ask what type of feedback you are using primary or secondary?
Registered Member #2288
Joined: Wed Aug 12 2009, 10:42PM
Location: Cambridge, MA
Posts: 179
Der, I feel stupid... retuned it with the base grounded and it works great (in fact much better than before, gives a good 4-5" at 50 watts. Now I just need to get more than 100V on the bus. Retuned it sits at 385khz with the base grounded, 50khz detuned from a floating base.
It is a primary feedback driver with a discreet gate driver board and high side floating power supplies (I hate GDT's!)
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Don't feel stupid! it's how we learn! I have made my far share of mistakes like this, the only reason I know how to fix them is because I made the mistake in the first place and learned how to fix it. So all is good!
May I also ask what IGBTs you are using? At 535KHz they must be some fast little buggers.
Don't discredit the humble GDT It can do amazing things if you know how to get on there good side I use a single GDT to drive 4 CM600HA-24H IGBTs in my big 7 foot tall DRSSTC and I don't have to fuss with floating power supply or a bunch of extra complex gate drive and it still manages to pump out 13+ feet.
Registered Member #2288
Joined: Wed Aug 12 2009, 10:42PM
Location: Cambridge, MA
Posts: 179
They are HGTG 30N60B3D IGBT's... not the fastest things, I do need to get some faster ones at some point but I want to work out all the bugs first. Seems my optical receiver latched high and a bunch of stuff burned out so it needs repair, but it's definitely working pretty well now (aside from being in a burned out state)
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
DRSSTC Grounding Issue (Ground Base, Kills Coil)
It can do amazing things if you know how to get on there good side 
I use a single GDT to drive 4 CM600HA-24H IGBTs in my big 7 foot tall DRSSTC and I don't have to fuss with floating power supply or a bunch of extra complex gate drive and it still manages to pump out 13+ feet.
-> 
