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 #103
Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845
Ok, I was looking at an old GDT I once made out of the wrong core material, and it got me thinking.
Say I have a ferrite ring to form a magnetic circuit, and I want to store as much flux as possible in that circuit in the shortest amount of time (ie drive it to the point just before saturation). But what would be the quickest and most efficient way to do this, with a large mmf (ampere turns) value or with a low mmf value?
I've been googling and wiki'ing, but I don't fully understand reluctance. I guess what I'm trying to say is 'Is the maximum rate at which you can drive a core to saturation defined by its reluctance in the same way the maximum rate at which you can drive a current through a wire or coil is defined by it's inductance?'
So that would mean with a high reluctance, it would be most efficient to use a high mmf value (many turns, low current) to 'slowly' drive the core towards saturation, at the maximum rate defined by the reluctance of that core material. The current could therefore be self limited by the resistance of the large number of windings, resulting in the fastest AND most efficient way to saturate the core (correct number of turns, and therefore current for the reluctance of the material you are trying to saturate). Is this paragraph correct?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Bear in mind that this post is powered by a large amount of beer so YMMV.
The question you're asking doesn't make sense. The amount of magnetic energy that the core stores when driven to saturation is always the same. So it doesn't really matter how you drive it, no method is more "efficient" than any other.
Saturation is always caused by the same amount of ampere-turns, no matter the amount of windings you use. But since I=(1/L)*integral(V dt), and L is proportional to turns squared: the more windings you have, the longer a given voltage will take to get the current to the saturation level.
So the quickest way to saturate the core is to slap a very high voltage across a winding with only a few turns. And according to the first point above it's no more or less efficient than any other method.
Saturation is usually regarded as a bad thing that we try to avoid, except in certain circuits (saturable reactors for power control and pulse compression)
Reluctance is the magnetic analog of resistance. It's a measure of how many ampere turns you need to force a given flux density.
Registered Member #103
Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845
That makes sense now, thanks! So the only limitation in driving the core to saturation would be the ability to provide a sufficient current for a specified period of time, determined by the inductance of the whole mess.
I was thinking that the core provided some kind of resistance to accepting flux, so it could only accept it at a rate slower than you could physically apply the current, hence my thinking that applying the current slowly would be more efficient. I suppose I need to think less and read more
That's funny, this post is also fuelled by a fair amount of beer and I think I understand it now.
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.