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 #40981
Joined: Thu Nov 21 2013, 08:40AM
Location: Hong Kong
Posts: 12
Hello everybody at 4hv! New here~
So I've been planning to build a DRSSTC and was wondering if this IGBT would work: FGH80N60FDTU I have a lot lying around and i saw that they have similar specs compared to the other popular IGBTs
And i also want to know what or how should i find out the voltage rating should i get for the Tank Caps
Btw I'm only in highschool so yeah I'm kind of semi experienced in this stuff only,so help would be appreciated
Expected specs: 0.2uF MMC 4 inch OD secondary coil 30 inches tall 8 inch OD primary tapped at 5~7 turns Resonance at 130 khz Using custom layout Steve Wards 2.0 driver Self made interrupter Runs on 220v mains directly Full bridge design
Mostly copied from schematics online and changed to meet my needs ~
The capacitor voltage rating has to be determined by the maximum ringup voltage expected in the primary, which is a factor of the burst length in cycles and whether your inverter uses a full or half bridge. You have to choose a burst length that won't exceed your maximum pulse current or cap voltage, and determining that mathematically isn't easy.
I started a few threads, emailed a lot of experienced builders, and spent a month trying to nail down a procedure for the math but ended up largely unfinished. I got close to a firm formula but couldn't confirm it since I don't have a DSO (only an analog CRO).
If you don't get anywhere let me know and I'll try to dig up my work on the subject and pass it on to you.
I suspect that most builders just go with rule of thumb known good parameters, but surely someone has a finished mathematical method of choosing Vcap and Burst length based on available Vbus and Iocd!!
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
The day someone comes up with an accurate model of streamer loading, I'll publish that method. Until then, you might like to try the following rules of thumb:
Dimensions of coil: Same rules as classic sparkgap coils apply, but aim for a "stubbier" secondary as this helps achieve better coupling and a lower resonant frequency. Smaller DRSSTCs need somewhat more turns than a sparkgap coil of the same size, otherwise the frequency gets too high for efficient operation of IGBTs. Try to keep it below 200kHz for 600V discrete IGBTs and 100kHz for 1200V bricks.
Secondary impedance = sqrt(Lsec/Csec) = 50k to 100k (JavaTC will tell you this) In small coils you will need to compromise between too high secondary impedance and too high frequency. Beginners should probably go for lower frequency and higher impedance.
Primary impedance = sqrt(Lpri/Cpri) = 10 to 20 times (4/pi)*(Vbus/Iocd)
The above rule fixes Lpri/Cpri. Also, the primary must resonate at the same frequency as the secondary and this fixes Lpri*Cpri. So, you have two equations from which you can calculate the two unknowns, Lpri and Cpri. Allow about 20% more primary inductance so you can detune to compensate streamer loading.
Tank capacitor voltage rating = 10*Vbus (approx) or Iocd/(2*pi*fres*Cpri) (more accurate)
Burst length = 150 to 300us
Coupling = 0.15 to 0.25
Anywhere within this range seems to give a good performing DRSSTC. Higher values of coupling tend to suit lower primary and secondary impedances, and vice versa.
The day someone comes up with an accurate model of streamer loading, I'll publish that method. Until then, you might like to try the following rules of thumb:
What about a formula for an unloaded coil? This would give you an upper end worst case scenario you could use to determine parts ratings. If there is no loading the you can determine the maximum voltage the cap has to withstand before the OCD kicks in to limit current.
Steve Conner wrote ...
The above rule fixes Lpri/Cpri. Also, the primary must resonate at the same frequency as the secondary and this fixes Lpri*Cpri. So, you have two equations from which you can calculate the two unknowns, Lpri and Cpri. Allow about 20% more primary inductance so you can detune to compensate streamer loading.
Tank capacitor voltage rating = 10*Vbus (approx) or Iocd/(2*pi*fres*Cpri) (more accurate)
Burst length = 150 to 300us
Coupling = 0.15 to 0.25
Anywhere within this range seems to give a good performing DRSSTC. Higher values of coupling tend to suit lower primary and secondary impedances, and vice versa.
How does burst length factor into that formula? In other words, how would you modify the formula to allow much longer bursts, perhaps 500-750uS? Burst length is significant in terms of half cycles so fres would need to enter in somewhere as well. This is the root of the problem I was trying to address in my previous work.
Btw, thanks a ton for the rules of thumb above, they're invaluable!
Registered Member #40981
Joined: Thu Nov 21 2013, 08:40AM
Location: Hong Kong
Posts: 12
Well heres a pic of my coil, i know it might be a little crude especially the primary coil. But I want it functioning more than i want it looking good since its my first drsstc :D so what do ya guys think?
And also what do you think of this IGBT FGH80N60FDTU Link to datasheet:
I'd avoid wood near the primary though, it becomes a conductor at high voltages. You're one primary strike away from a carbon path that'll destroy the entire coil if you use wooden supports.
Registered Member #40981
Joined: Thu Nov 21 2013, 08:40AM
Location: Hong Kong
Posts: 12
Ok I'll change it to acrylic supports then thx for the feedback and also I've been wondering Steve Wards 2.0 Driver has only 1 output do I connect all 4 GDTs to it as im running a full bridge cuz ive only seen schematics that connect 2 for a half bridge And I tell you it wasn't a good start at all XD the coil took weeks to wind and paint because I had so little time to work on it every week the lacquer on it isn't even sanded down. It might look good in the photo but it really is ugly ;)
Registered Member #40981
Joined: Thu Nov 21 2013, 08:40AM
Location: Hong Kong
Posts: 12
Here's the driver based on Steve Wards 2.0 Universal Driver I made into a single sided board with unfortunately a lot of jumper wires, I haven't scoped it yet so I don't know how well it'll do but I'm sure the power supply rails are at good voltages and stable ,I'm just afraid the 90° PCB traces will mess up the signal...sigh~ I didn't realize it till i finished the board...
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
wrote ...
What about a formula for an unloaded coil? This would give you an upper end worst case scenario you could use to determine parts ratings. If there is no loading the you can determine the maximum voltage the cap has to withstand before the OCD kicks in to limit current.
The formula I gave above for tank cap voltage rating covers this case.
wrote ...
How does burst length factor into that formula? In other words, how would you modify the formula to allow much longer bursts, perhaps 500-750uS? Burst length is significant in terms of half cycles so fres would need to enter in somewhere as well. This is the root of the problem I was trying to address in my previous work.
Because we don't have an accurate streamer model, we don't know in any detail how the streamer load develops with increasing burst length. So I assumed the streamer load to be unchanging with burst length, and that is why burst length doesn't appear in the formulas.
In practice, we know that the load gets heavier as the streamer develops. This means that a coil designed for long bursts should have a somewhat higher impedance primary and lower impedance secondary: the magic number in the primary impedance formula I gave should be nearer 20 than 10, and the secondary impedance nearer 50k than 100k. (Or maybe even lower than 50k as you will find in QCW coils)
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.
First DRSSTC questions
Until then, you might like to try the following rules of thumb:
