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 #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
Hello all, So i got a U126/91/20 core from ferroxcube awhile back, and I am actually doing stuff with it now. I plan on using a L298 for a H-bridge design. I plan to start with hard switching, and then later move on to SLR topology. Input will be voltage will be 330v, and a maximum of 10A (limit of my fuse right now). I will be using STGW30NC60W IGBT's. I made a bobbin with 1/8" acrylic, and i am using 30 AWG wire. the insulation thickness is.005 inches. Here are some pics: A picture of old PVC bobbin vs. the new one.
The bobbin look horrible, but i say its pretty good for only using a acrylic sheet and a Xacto knife to make it (lots of scoring and breaking).
Any comment/questions/suggestion's for the driver (like frequency)?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Cool core. Be careful when handling it, I got two monster cores from old TVs and even with normal handling, they developed some chips and dents around the area where the core halves touch.
I would go with ~50kHz for a first try.
Remember that the square wave drive puts out a lot of harmonics so you can excite the transformer's self resonant frequency even if it's magnitudes higher than your drive frequency. For this reason I tune the driver at low power with unloaded transformer to a frequency close to the intended one, at which it draws the least current.
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
Yep, i already got small chips, and one bigger chip.
I heard somewhere (can't recall where) that due to some reason, the voltage output will be double than what your turns ratio will tell you. If i have a 10 turn primary (enough turns?) then estimated output would be around 5kV. Would the out put be 10kV? For SLR topologies, everyone uses either a external inductor or with high leakage winding's. Is there anything wrong with gapping the core?
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
Nice core. You probably heard it here. And yes, the 2 * ideal ratio thing seems consistent.
Gapping the core ruins open circuit performance because the open circuit inductance will be close to the short-circuit inductance. With an ungapped core the open circuit resonant frequency will be so low that almost no current is drawn, which is good. Really, gapping the core is only useful in SLR as a last ditch effort to reduce the value of leakage inductance. If you fear that the leakage inductance will be too high then wind the transformer with good coupling, ie windings underneath eachother, and use an external inductor to get the required inductance.
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
Thats good, i ran short of wire so there are ~150 turns. If you look at the first picture, it wound to about a cursor width to the left of the white tape.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Uzzors wrote ...
Gapping the core ruins open circuit performance because the open circuit inductance will be close to the short-circuit inductance. With an ungapped core the open circuit resonant frequency will be so low that almost no current is drawn, which is good. Really, gapping the core is only useful in SLR as a last ditch effort to reduce the value of leakage inductance. If you fear that the leakage inductance will be too high then wind the transformer with good coupling, ie windings underneath eachother, and use an external inductor to get the required inductance.
Well, you don't want any gap with bridge inverters, especially with the SLR. Even a very little gap often alters open circuit performance greatly.
AFAIK the gap does not do much with leakage inductance (if something then increase it)...
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
I will probably go with a external inductor on a wire spool (ID about 1inch). Wont the inductor filter some harmonics? How do you think those IGBT's i posted will stand up? I can't find anything on there current rating vs. frequency. On richard burnet's(?) site, i saw some thing about putting 2 or more H bridges together to distribute the power for induction heating. Would this same setup work if i split the inductor between them? I finished the secondary. I ran out of wire so you can see the extra space on one side.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
rp181 wrote ...
I will probably go with a external inductor on a wire spool (ID about 1inch).
Why? Just wind the primary opposite the secondary, this should provide just about right leakage for experimental arc drawing. If its too big, spread the primary turns. If its too small, wind the primary in layers (so that the effective "core surface" under the winding is smaller). Edit: Changing the leakage also changes the resonant frequency.
rp181 wrote ...
Wont the inductor filter some harmonics?
no, but it adds inductance decreasing the system's resonant frequency.
rp181 wrote ...
How do you think those IGBT's i posted will stand up? I can't find anything on there current rating vs. frequency.
They should be good to at least 100kHz or a bit more. Be sure to include clamping diodes on them (at least 30A high-speed diodes).
rp181 wrote ...
On richard burnet's(?) site, i saw some thing about putting 2 or more H bridges together to distribute the power for induction heating. Would this same setup work if i split the inductor between them?
Maybe, but just paralelling the transistors should have similar effect. I don't know exactly how big is your core, but these IGBTs in a full bridge should be able to supply ~4-8kVA powered from rectified 230V (or doubled 120V).
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
I didn't think winding on opposite legs would be enough, but it sounds good. If you go to ferroxcube's website, core sets, U, its the last one on the list.
EDIT: I plan on making a final bobbin much like finn hammer's so i can tap it for different voltages. What gauge wire to you guys recommend? I wan't to keep it in air, but i will put it under oil if i have to.
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.
My ferrite core SMPS
