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 #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
GammaRay Don't know about this, but the transformer can make voltage pulses, with a type of buck converter to level out the pulse to a low voltage level
GammaRay, may I suspect that the demand of HV-LV transformation arised from the plan of catching the energy of a lightning bolt using the capacitive storage? ;) Did you actually managed to do that?
You may connect a chain of small LV caps in parallel to the HV bank - this way you will have many LV sources to transform. Ensure that voltages at all caps are balanced (use TVS for each cap) - all those little sources must be drained simultaneously with the same speed and have precisely the same capacitances. F.e. use 20 caps 1KV each; then wind 20 equal isolated primaries on a huge toroidal ferrite core with just one secondary. With a step-down flyback topology, synchronously switching on all primaries at once, you will ensure the energy draining will keep all voltages on caps at the same level. Transform this into 12VDC to charge a Lead battery of a UPS, so you will get 120VAC as well. :)
Registered Member #816
Joined: Sun Jun 03 2007, 07:29PM
Location:
Posts: 156
I was about to suggest the same sort of idea as Yandersen just pointed out, only using many stages of half bridges in series as the ac would be half the stage bus voltage. The gate drives transformers would be similarly bulky as would have to isolate 20kv and have as many windings as igbts used. Even if you used the highest voltage devices you could find plus you’d still need some overhead.
While all the options seem to have been discussed from mechanical, vacuum tube or series semiconductor however you arranged them. Also it would have to work over a very wide range of voltage as the capacitor discharged. Most of the energy would be in the higher voltage end of the range, so you could just opt to operate over, for example 3:1 input voltage range.
Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276
Electra wrote ...
I was about to suggest the same sort of idea as Yandersen just pointed out, only using many stages of half bridges in series as the ac would be half the stage bus voltage. The gate drives transformers would be similarly bulky as would have to isolate 20kv and have as many windings as igbts used. Even if you used the highest voltage devices you could find plus you’d still need some overhead.
While all the options seem to have been discussed from mechanical, vacuum tube or series semiconductor however you arranged them. Also it would have to work over a very wide range of voltage as the capacitor discharged. Most of the energy would be in the higher voltage end of the range, so you could just opt to operate over, for example 3:1 input voltage range.
He could do Yandersen's ideas and use high speed optocouplers.
Well, one for sure is that assymetrical halfbridges will be required to charge primaries as coupling factor with 20KV isolation over the core will be too bad. Most of IC halfbridge drivers have 600V bootstrap voltage, so that will be the limit for a single stage. As voltage range has wide bounds (0-600V), the time the primaries will build up the desired current level is not constant also (the higher the voltage, the faster the current rises). To control the charge duration without the need of controlling the voltage, we can put a shunt resistor in series with a chain of dividing caps (insert the shunt between Gnd and the "bottom" cap) - once all stages are told to start energising, the voltage drop on a shunt resistor starts to linearly rise. Once it reaches the desired value, we close all stages and wait until the portions of sucked energy will unload into the LV load (flyback topology). Then we start the charging cycle again.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I've just had a pretty simple idea, use a high value resistor and a high voltage triode to charge a capacitor bank to a pre-determined voltage, say, for arguments sake, 120V (doesn't really matter), then drive whatever load directly from that, (or use an SMPS, or whatever, to 'transform' the voltage to whatever you want.
Just keep turning on the triode to maintain the voltage in the second, low voltage, capacitor bank within the upper and lower limits (whatever you decide).
While this will require a large capacitor bank, and a HV resistor (or string), and a HV triode, it won't require the multitude of sections proposed in some of the suggestions here.
The HV resistor is just to limit the current to a reasonable level to be controlable, and the value could be reduced as the HV capacitor bank becomes depleted. (if you use a string of resistors, just switch some out of the string as the HV capacitors become depleted, maybe in conjunction with switching the triode on for longer periods.)
The current rating of the triode and the total capacitance of the low voltage bank will be dependant on the load being driven.
Registered Member #8120
Joined: Thu Nov 15 2012, 06:06PM
Location: Moscow, Russia
Posts: 94
Ash Small wrote ... I've just had a pretty simple idea, use a high value resistor and a high voltage triode to charge a capacitor bank to a pre-determined voltage, say, for arguments sake, 120V (doesn't really matter), then drive whatever load directly from that, (or use an SMPS, or whatever, to 'transform' the voltage to whatever you want.
That sounds a lot like a linear regulator. Thus, efficiency will be 120/20000, or essentially zero. Right? Or did i read it wrong?
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Artlav wrote ...
That sounds a lot like a linear regulator. Thus, efficiency will be 120/20000, or essentially zero. Right? Or did i read it wrong?
You may be right, maths isn't my strong point, but you'll only need sufficient resistance to make the current managable. This will depend on the amount of pulsed current that the triode can handle, and that will depend on what HV triodes are available.
As I=V/R, my calculations suggest that to limit current to, say, 100A pulses, you'd need 200 Ohms.
To limit it to 20A pulses you'd need 1kOhm.
I'd need to google available HV triodes in order to take it any further.
EDIT: I suppose you could use a series string of 20 or so mosfets, I've seen various circuits that can achieve this successfully.
EDIT: Maybe the 1/2CV^2 thing makes this less efficient than other methods, along with the resistor losses. As I said earlier, maths isn't my strong point. I generally just copy formulae into spreadsheets or whatever to do number crunching.
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.
Rare HV to LV converter
