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 #4134
Joined: Tue Oct 11 2011, 12:34AM
Location:
Posts: 5
Hello again! Well it seems my curiosity about vintage tesla coils led me again to discover a strange (for me at least) tesla coil. I'm posting the picture below. So I have a couple of questions, because I can't understand completely how it works.
1) It seems that there are three coils in total, two secondaries and one primary in the middle. I put it on the JAVATC (it accepts only one secondary and primary) and it gave me back that primary is tuned 50% higher compared to the secondary. It oscillates at around 700khz and the secondary at around 350khz. Is JAVATC wrong or this is the case here? My guess was that this happens because primary has to transfer energy to both secondaries so 350+350=primary's frequency?
2) Why are the two secondaries literally connected to the primary this way? Each secondary has one side of the coil connected to one side of the primary. Does this give some kind of tuning?
3) Does this work as a bipolar tesla coil? And because I am very curious about how it works in real life and I'm willing to build one, how could I tune a bipolar tesla coil like this one?
Thank you very much for your time and any forthcoming help!
Looks like a pretty standard Bipolar SGTC to me. The only strange thing is the low secondary turns count; 140 in total.
It isn't really two secondaries, there is just one secondary and the primary is overlaid in the center - the primary and secondary are not directly connected, it just appears this way because of the drawing.
edit: removed an error my tired eyes should have caught!
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
I agree each side of the secondary is connected to one of the ends of the primary, making some kind of bipolar air-core autotransformer with a ratio of 1:15 or something
Registered Member #4134
Joined: Tue Oct 11 2011, 12:34AM
Location:
Posts: 5
Thank you both for your answers! So if the secondary is actually connected to the primary, how do I fine tune it? Is the primary oscillating at double of each secondary's frequency or both 3 coils have to to resonate at the same frequency? I mean Xfreq of secondary + Yfreq of the other secondary = primary's frequency, or X=Y=Primary's frequency? Even following your method Sigurthr, JAVATC gives me back that primary is tuned 43-45% higher!
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Use one half of the secondary in JavaTC.
The other half is identical, so the ends must develop equal and opposite voltages, hence the centre must be at ground potential. It follows that you get the same resonant frequency if you cut it in half and replace the missing half with a ground plane. (this is called the method of images)
Because the primary voltage is much smaller than the secondary voltage, this argument is still more or less true if the secondary is connected to the primary.
Registered Member #4134
Joined: Tue Oct 11 2011, 12:34AM
Location:
Posts: 5
I see...Thank you Steve, I just tried it your way and it seems that either they built it out of tune on purpose or they didn't have JavaTC to calculate the exact length of wire they needed! Lol! I have an idea though as to why they built it this way. The coupling coefficient in bipolar coils is usually huge and we need much bigger formers for primaries in order to avoid internal coil sparks. JavaTC gives me back a number 0.4 to 0.7 (depending on the former size) when it is perfectly tuned. So at this coupling, lots of internal sparks are to be expected and so I think they made it out of tune on purpose to avoid this kind of phenomena. When it is given as they did it, the coupling is around 0.20 to 0.25. Just a theory though...We'll see what happens when I have it ready...
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.
Strange old Tesla coil no2
