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 #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Tony Matt wrote ...
In a pancaque the 51th turn is wond on top of the 49th turn, the 52 turn is on top of the 48th turn ..........the 99th turn is on top of the first turn. ( the voltage between the 49 and 51 may be 56V only , between the 48th and 52th may be 96V and so and so ) if a layer of 50 turns is running at 28V per turn the total volt per layer will be 1400V ( between the first turn and the 50th turn) Then the voltage between the first turn to the 51th turn will be 1428V,.... and the voltage between frst and the 100th will be 2800V ...Note that the 100th turn is laying on top of the first. So, the insulation between layers has to be sized to manage 2800V plus a safety factor.
I am planning on winding the 51st turn superjacent to the first turn. There is plenty of room in my secondary design to wind the first layer, then wind some insulation, then take the wire back to the start, then wind some more insulation, then start the second layer. This gives 1400V between any subjacent and superjacent turn. I believe others have said this also reduces inter-layer capacitance, as well as requiring less insulation.
Tony Matt wrote ...
Yes, the leakage dispersion inductance is a pain when you deal with hV transformer that requires big distance between the coils. The the goal is to keep 100kV insulation between any pancake and primary, 100 kV between any pancake and core, 25 kV beween any two sequencial pancakes (if 4 pancakes are in the secondary). As the secondary pancakes are in series and works as a uniique secondary coil the leakage inductance is not different in both arrangements. But for construction, a unique primary simplifies the construction a lot.
A unique primary would simplify construction greatly, but the 'pie winding' method illustrated above is supposed to reduce leakage inductance by , I think, keeping all the flux within the windings. Unique primaries don't do this, apparently. The 2:4:4:2 arrangement of the primaries is supposed to equalise the flux between the three secondaries, as I understand it. I think it also reduces capacitance within the windings.
I wonder if winding two parallel primaries, one under the secondaries, and one around the secondaries would have any benefits over using just one, either under or over the secondaries?
It looks like I may have to wind a few different ones, and then measure resonance, etc.
Registered Member #3700
Joined: Sat Feb 19 2011, 12:59PM
Location:
Posts: 107
Ash: If you wind the 51st turn superjacent to the first turn the max inter layer voltage will be 1400V and save insulation asd space .
I never have try this, am affraid that in the end could be a trouble when the wire make the transposition from the 50 to 51th turn and will require more insulation....
As you want to wind and experiment a few different primaries the pancakes shall be self supported and rigid to allow be assembled and dissasembled several times.
Why not use circular bobin forms? Eliptical or oval forms are a nightmare to wind. Try to wind just one pancake to verify the dificulties. You may use kraft paper from liquor store, free....
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
A circular bobbin won't fit in the 'window'. I'm using two sets of cores side by side to get the Bmax that I need.
I realise the difficulties involved in winding an eliptical form, but it's not really any more difficult than winding onto a square form. You just have to maintain the correct tension.
Registered Member #3700
Joined: Sat Feb 19 2011, 12:59PM
Location:
Posts: 107
Hi Ash, Here one suggestion. This dwg is only to open the discussions, DO NOT use for construction. The core dimensions is not clear for me, you can check and correct. Regards
EDIT: because the core window is small, I believe that it will be nescessary to provide a secondary center tap and ground togheter the ferrite core, limiting the HV gradients. The final drawing will provide informatio for this requirement
Registered Member #3343
Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311
Hi Ash 1
I just was comparing your drawing with the Tony dwg...
The core do not provide too much room for the 100kV insulation between the pancake and core, ( and between the pancake and primary), so the secondary has to be ct and grounded with the core . In this way the max voltage between core and pancakes will be 50 kV ( and 52 kV for pancake to primary )
If the primary stray inductance is about 5uH , the reactance @ 25kHz will be about 0.82 ohm, So the voltage drop at 20A could be 16 volts. I think this is acceptable, for a high voltage transformer.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Newton Brawn wrote ...
Hi Ash 1
I just was comparing your drawing with the Tony dwg...
The core do not provide too much room for the 100kV insulation between the pancake and core, ( and between the pancake and primary), so the secondary has to be ct and grounded with the core . In this way the max voltage between core and pancakes will be 50 kV ( and 52 kV for pancake to primary )
Hi Newton, centre tapped and grounded does sound like a good idea, as long as the insulation between core and primary is sufficient, thanks.
Newton Brawn wrote ...
If the primary stray inductance is about 5uH , the reactance @ 25kHz will be about 0.82 ohm, So the voltage drop at 20A could be 16 volts. I think this is acceptable, for a high voltage transformer.
Do you have another core with larger window ??
That will be a last resort, I'm more interested in minimizing the stray inductance and capacitance at the moment. I think I can get sufficient insulation using a combination of oil and plastic,
Newton Brawn wrote ...
PLS confirm the inter layer insulation thickness.
tks
I'm planning to use 1mm insulation between layers, oil impregnated kraft paper, but I think it could be a bit more if I need to reduce inter layer capacitance
My main questions at the moment are these: " Will Tony Matt's design using six pancakes have less capacitance than my design using three pancakes?" And "Will my design using 'pie windings' have less stray inductance than Tony's design using a primary over the secondaries?" Which leads to the question "Which design will have the higher resonant frequency?"
My 'gut feeling' is that six smaller capacitors in series will have less capacitance than three larger capacitors in series, for the same overall voltage, but that the 'pie windings' will reduce stray inductance.
As I'm not a mathematician, I'll have to build both, and measure them, I think.
I hope to post some more drawings later this week, if I get time.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
Just a small note for multi-layer secondaries to increase resonant frequency wind one layer then run the wire across the windings back to the start of the layer then start a new layer, i.e. all layers are wound left-to-right (or all layers are wound right-to-left) insulate as required. This technique reduces the voltage stress to half and the inter-layer capacitance to one quarter - doubling the resonant frequency .... ideally. I've tried it and it works.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Sulaiman wrote ...
Just a small note for multi-layer secondaries to increase resonant frequency wind one layer then run the wire across the windings back to the start of the layer then start a new layer, i.e. all layers are wound left-to-right (or all layers are wound right-to-left) insulate as required. This technique reduces the voltage stress to half and the inter-layer capacitance to one quarter - doubling the resonant frequency .... ideally. I've tried it and it works.
I was planning to do this anyway, Sulaiman, although I'm not certain it actually does improve the voltage stress.
Say you have 1mm insulation between layers, and each layer is 1.25kV, If you wind right to left, then left to right, you have 2.5kV between the beginning of the first layer and the end of the second layer, so 2.5kV per mm of insulation. If you wind right to left, then wind 0.5mm insulation, then take the wire back to the start, wind another 0.5mm insulation, then wind the second layer right to left, you have 1.25kV between the beginning of the first layer and the end of the wire that you take back to the start after 0.5mm insulation, and the same from the start of the 'return wire' and the end of layer two.
1.25kV over 0.5mm insulation still equals 2.5kV per mm, or am I missing something?
I believe you've mentioned before that it decreasers inter-layer capacitance, but I didn't realise that it reduces it by so much. Thanks.
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.
Calculating self-resonant frequency of HV Transformer?
