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 #1739
Joined: Fri Oct 03 2008, 10:05AM
Location: Moscow, Russia
Posts: 261
Sorry for hijacking the thread, but I don't feel like opening a new one of the sort of "let's flood on something I'll probably build one day, but mostly it's a troll stuff so far"-thread, but still want to ask this one :) I decided to start a new coil, a tiny DRSSTC - somewhat like Reaching's DRSSTC 5. As a driver I decided just to make a ripoff of my older schematic with the only difference being the OCD. However here is the tricky part - as far as Reaching's research proves, FETs are not the best choice for a DR coil. However I still have no idea why - running 100A means we are still within the safe rating of those 30A switches (I decided to use those as they cost only $1.5 here - the cheapest switch which performs way better then IR FETs, at least in non-DR coils) rated 120A peak, and running in full bridge means we are running less then 50A mean current - pretty good headspace for breakrate. For the secondary I plan to use, a 20x5cm @ 0.08mm wire, the estimated 300-500w feel like a proper power, so everything feels just so perfect and shiny - and like always it makes me wonder what exactly am I missing ;)
Registered Member #1739
Joined: Fri Oct 03 2008, 10:05AM
Location: Moscow, Russia
Posts: 261
Well, what you say is surely right for the bigger coils, however you are missing my point ;) First of all, I'm not planning overloading the switches - feels like 100A is enough for the small scale of the coil, and the datasheet permits this operating mode. Also, using FETs will require less drive voltage, thus it will not force me to use the 40v driver ICs and hold up with the good old +12/-8 driver concept. Even more - the FETs don't have that much of a tail, thus we don't have that much shoot-through at the cost of higher dissipation in open mode (and with 200+ kHz running frequency this may become an issue). So - it all needs some closer look ;)
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Your questions in your post are okay IMHO. Just your title, "I need every help available" is a bit over the top. A title such as "a couple DRSSTC questions" would probably be more receptive to positive responses.
Registered Member #289
Joined: Mon Mar 06 2006, 10:45AM
Location: Conroe, TX
Posts: 154
LL, I don't know what MOSFET you’re talking about, but let’s say it's got an Rds on of .05 ohms and we're comparing it to an IGBT with a Vce of 1.5V. These are typical values, just for the purposes of comparison, so let's also assume all of the other specs to be that same (rise, fall times, etc.) and that we’re switching 100A. This means the conduction loss for the MOSFET is 100*100*.05=500W and the loss for the IGBT is 100*1.5=150W. The MOSFET will dissipate 66% more power while it’s on than the IGBT. IGBTs are the way to go for high current; period. If your coil has a frequency that you think is too high to use IGBTs with, lower the frequency.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
LithiumLord wrote ...
Well, what you say is surely right for the bigger coils, however you are missing my point ;) First of all, I'm not planning overloading the switches - feels like 100A is enough for the small scale of the coil, and the datasheet permits this operating mode. Also, using FETs will require less drive voltage, thus it will not force me to use the 40v driver ICs and hold up with the good old +12/-8 driver concept. Even more - the FETs don't have that much of a tail, thus we don't have that much shoot-through at the cost of higher dissipation in open mode (and with 200+ kHz running frequency this may become an issue). So - it all needs some closer look ;)
MOSFETs - Conduction Losses = Rds*I^2
IGTS - Conduction Losses = Vsat*I
Obviously, the square term for MOSFET conduction losses is going to have much more losses as current increases.
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.
I need help with a DRSSTC, in everyway possible?
