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 #512
Joined: Sat Feb 10 2007, 05:42PM
Location: Chico, CA
Posts: 25
An update, So I ordered the famous 942C20P15K(non-stock) MMC caps from rell.com last week. The plan was to have 8 kv at 33 uf. That would be around 9 strings of 4. Running through some threads on this board, I realized that may not get them in time. So that leaves me with the other option of using the GE 42L series capacitors. How do i make the transition since the GE aren't so sturdy? Will I need longer strings?
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Well, it really depends on the power level. The GE42L caps are OK for DRSSTC in particular, because its the RMS current rating of the cap that matters much more than the peak rating (which is what the 942C excells with). What 42L cap do you have? And, what is the expected power level you want to run at? Answer that and i can make a suggestion for how many parallel strings are needed.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
I(rms) = sqrt((ONtime/OFFtime)*0.7*I(pk)^2)
That looks familiar... did i post that somewhere or did you happen to come up with the same .7 constant? Anywho, close enough to real life.
Typically, the larger of this 42L series is 9 to 11A RMS rated. So you would need ~13-16 strings and enough in series to handle the 7kV and maybe a bit more for headroom if you want them to last a really long time (ive tested the 1200V 42L caps to 2500V in DRSSTC use... on accident... they start snapping like little fire crackers).
The 942C caps you have are only rated to 13A i think, so you would still want many more parallel strings than you planned on.
My suggestion : lower your duty cycle to reduce the RMS current. 400uS is really too long in my opinion. You will probably find that 200uS is enough if you are supplying ~650VDC. Efficiency really seems to drop off past 250uS (you get longer sparks, but at the expense of much higher input power).
Registered Member #512
Joined: Sat Feb 10 2007, 05:42PM
Location: Chico, CA
Posts: 25
I got that rms formular from the drsstc wiki. Good news, I spoke with a rep from rell, and ordered the -f roHS compliant 942 capacitors instead, which are in stock. I got 65 of those.
Working out the new numbers, for 148 amps, i'll need 12 strings of 4. For now, I'm only planning to use 440 volts (220 doubler) as in input for my coil. Do you think I'll still be able to pull some decent spark length?
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
wrote ...
How do i make the transition since the GE aren't so sturdy?
Who says the GE capacitors aren't so sturdy? We use them exclusively in our solid state coils and have had practically zero failures with these type of capacitors.
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 PRIMARY CAPS
