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 #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
I have searched google but can not find the derivation. I know how to derive the inductance for a solenoid, but does anyone have a link or reference where I can see the derivation for inductance of a flat spiral based on its geometry (inner radius, outer radius, turns)?
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
First, the derivation of inductance for a solenoid applies to 'infinitely long' solenoids Mr. Wheeler did lots of measurements to arrive at the empirical equation that we commonly use. For arbitary solenoid dimensions I'm not aware of a simple explicit derivation, any references?
Similarly for a spiral coil the equation is also I believe empirically derived.
Registered Member #29
Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500
That is for an idealised long solenoid.
Derivations for realistic coils is difficult, but possible if certain assumptions are made (e.g. the conductors are infinitely thin). Numerical methods are needed for "real" coils..or approximations (like Wheeler's formula).
I have attached a few pages of S. Ramo, J. R. Whinnery and T. Van Duzer, Fields and Waves in Communication Electronics, Second Edition, 1984. These pages give some of the mathematical background if you want to develop your own software to compute inductance of real coils....(which in reality, would not be too difficult to do if you are familiar with some basic numerical methods). Have fun!
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
Wheeler and versions thereof are good for giving a few percent accuracy for many coil geometries. However, you can get surprisingly good estimates from very gross approximations to the coil shape, if you are happy with 10-20% accuracy and a feel for what is going on.
1) Estimate the path of the 'average' field line.
2) Its distance from the average conductor gives the H field for unit current in the coil
3) The H field and the line length give the mean B field
4) The average conductor area and the B field gives the flux linakge per unit current, which is the definition of the Henry!
If the air path is replaced by ferrite or iron, then the above method becomes extremely accurate, the estimates replaced by measurements of the actual core.
If the air coil is very extended, like a Tesla primary, or secondary, then the estimates become very flaky indeed, but it's still worth doing a) to get a physical feel for what is really going on and b) to make sure your Wheeler calculation isn't out by a factor of 10, or 25.4, or something silly.
For a compact "max inductance per length of wire" geometry winding, I got to within 3% of Wheeler with my approximation, your hand-waving may vary!
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.
inductance derivation
