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 #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Bert wrote ...
.. The marked non symmetrical shrinkage was probably due to the coin being constrained only on one side. ..., I've never tried shrinking with only one dowel rod in place.
I didn't use any dowel at all. It was slipped in to the split gap of the PVC but wasn't a good fit. The ice (presumably) filled the gap. I tried to avoid an air pocket but who knows.
Bert wrote ...
...The estimated open core (no coin) Wheeler inductance of your work coil was perhaps ~1.6 uH or so. The low power scope shot indicates that you got four complete cycles over a period of ~475 usec, for a resonant frequency of about 8.4 kHz. Assuming a 215 uF bank capacitance, your overall initial loop inductance (including "loaded" work coil, caps, switch, and bus bars) was about 1.67 uH - in the ballpark.
The system rings at 25kHz with a 6 inch wire in place of the coil giving a system inductance of 0.2 uH.
Bert wrote ...
Assuming 5 kJ of bank energy (~6800 volts) and no change in work coil inductance, the predicted current peak would be about 77 kA. However, we know that the coil stretched and expanded as the current increased. In order for the measured current peak to only be ~50 kA, the "effective" work coil inductance must have increased to ~3.9 uH, implying that the work coil expanded to an average diameter of about 1.7" by the first current peak. ..
So my measurements might be right. It also means I can push a lot harder with the power and still be within the caps ratings. Using 10kJ is not out of the question with my set up.
Bert wrote ...
.. In any event, I have little doubt that arcing is the source of your excess system losses.
What I really want to know is if my losses are less than with the plain coil. Is it worth pursuing the ice containment?
Bert wrote ...
.. I'd recommend repeating the experiment, but this time using a simple close wound coil of heavy build polyamide-imide magnet wire, centering the coin with identical dowels on each side, and simultaneously monitoring coil voltage and current.
Sounds like that is next. I have avoided voltage measurements as it means a connection to the HV which makes me nervous.
Bert wrote ...
And obviously, you also need to develop a more robust containment method before repeating the experiment.... :^)
If I don't have ice to absorb the energy I most certainly will.
Bjørn Bæverfjord wrote ...
What about using a photodiode to detect when the first arcs appear?
My camera (same as yours) goes to 1/8000sec so won't be too good for the 8kHz full cycle. It's all over by then. Just the time for a Rapatronic camera...
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Another good coin for shrinking is the canadian nickel. They are almost solid nickel so they are very conductove.
Have you actually tested this? I know (from first hand experience) that the american nickel is probably the most difficult coin to shrink (im not sure if its metal composition, though). Nickel is about 4X more resistive than copper. Aluminum (pure) is only 1.7X more resistive, and is much softer, so it should be by far the easiest coin to shrink.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
I forgot about this thread...
My camera (same as yours) goes to 1/8000sec so won't be too good for the 8kHz full cycle. It's all over by then.
What I meant was to use a photodiode to detect the arc and compare it to the current graph to make sure you interpret the current graph correctly. Try something new, learn something unexpected and all that.
Registered Member #118
Joined: Fri Feb 10 2006, 05:35AM
Location: Woodridge, Illinois, USA
Posts: 72
I've shrunk both types of nickels. A Canadian nickel (~100% Ni) actually shrinks somewhat better than a US nickel (75% Cu, 25% Ni). At 6300 Joules, a US nickel shrinks to about 92% of its original diameter, while a Canadian nickel shrinks to about 86.7% of its original diameter. Strangely enough, pure nickel is a significantly better electrical conductor than the cupro-nickel alloy used in the US nickel, even though the latter alloy is 75% copper. The Cu-Ni alloy only has 8% of the conductivity of electrolytic copper (IACS - International Annealed Copper Standard), while nickel has 22% of the conductivity (almost 3X better). A bit of nickel in copper really messes up its electrical conductivity.
Because it is so soft and has good electrical conductivity (~61% of IACS), aluminum coins are probaby the easiest coins to shrink - like Japanese 1 Yen coins.
Registered Member #354
Joined: Thu Mar 30 2006, 10:12AM
Location:
Posts: 55
GREAT. It would be very cool (also for me) if you test using a FLAT spiral coil. You can get lots of Teslas as it depends of coil volume that is very little. (the coin must be placed inside the coil center) I think that the coil must not suffer very much
Here it is an attached excel file used to design spiral coils ]1157465391_354_FT10774_flat_spiral.zip[/file]
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.