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 #9039
Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117
I am beginning to understand better how the SSTCs work and why they need suc high voltage on the primaries to throw sparks.
At such high frequencies (200kHz or so) there is not enough time for the current to build up beyond a peak of 100mA or so with say 12V input at the primary.
I used the standard AC formulas to do a rough calculation of current and around 0.1A is what came out out using AC impedance on the primary coil inductance and half bridge capacitors.
And this fits with my observation that my Tesla coil can only excite a fluorescent bulb but not throw any sparks with 12VDC input.
The GDT puts out a high frequency sine wave (on my oscilloscope) so surely the current flowing through the power FETs will effectively be high frequency AC.
Which in turn means the AC impedance formulas ARE good enough to calculate the peak current if you factor in the duty cycle that changes the effective voltage, e.g. 50% means half the input voltage.
So my fear about peak current getting so high that it starts melting wires etc is a great deal less likely than I had assumed.
Next on the agenda is to finish off my 120V DC power source.
I have one of those fuse box safety switch things (8A) on the primary coils of my series connected modified MOTs.
But I think I need to put in some fuses on the DC side just in case.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714
Comments from someone who has never made a Tesla coil of any kind.
Most "wound" devices can be rewound for operation with different voltage and current. Frequency, coil sizes and weights, magnetic field strength, electrical & mechanical power, and efficiency are invariant.
>>At such high frequencies (200kHz or so) there is not enough time for the current to build up beyond a peak of 100mA or so with say 12V input at the primary.
One remedy might be to use a primary coil with fewer turns, in proportion to the lower working voltage. Thus lower inductance by factor of about N^2. Resonant capacitance would have to increase by that same factor. Of course the number of turns can't be less than one.
For TC's of a given size and frequency, a useful metric for (say) the ability to throw sparks might be the primary voltage per turn.
Registered Member #9039
Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117
klugesmith wrote ...
Comments from someone who has never made a Tesla coil of any kind.
Most "wound" devices can be rewound for operation with different voltage and current. Frequency, coil sizes and weights, magnetic field strength, electrical & mechanical power, and efficiency are invariant.
>>At such high frequencies (200kHz or so) there is not enough time for the current to build up beyond a peak of 100mA or so with say 12V input at the primary.
One remedy might be to use a primary coil with fewer turns, in proportion to the lower working voltage. Thus lower inductance by factor of about N^2. Resonant capacitance would have to increase by that same factor. Of course the number of turns can't be less than one.
For TC's of a given size and frequency, a useful metric for (say) the ability to throw sparks might be the primary voltage per turn.
I was merely testing the primary with 12V so I was not really expecting anything spectacular.
I am feeling my way slowly forward with this thing and not making any assumptions.
I was not sure at all how much current was likely to be drawn by primary but my multimeter indicated something of the order of a few 10s of mA at 12V input voltage.
It was never the less enough to light up a fluorescent bulb held near the secondary so I know the circuit is working as expected.
Next I will test it with my 120V DC power supply.
If that goes OK then I may consider increasing the voltage to perhaps 220V DC - my caps are rated for 250V
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.
Primary coil current
