Winding a strong electromagnet

[capthook]

Hi folks, Does anyone know if a coil, an aircore coil for example when pulsed does the voltage rise instantly within a coil to max or close to the inputted voltage while it takes more time for current to build based on inductance?

You can also use this site: http://www.coilgun.info/mark2/inductorsim.htm

Enter the coil dimensions and wire size for many useful calculations including inductance, resistance, # turns and wire length.

[capthook]

I STILL can't get me brain around this - thinking I'm brain damaged! 

I have a magnet attached to the end of an electromagnet (EM) with a steel core and pulse the EM with just enough juice to get the magnet to drop off.

Which will require less energy input to get it to drop off?

1) a high permeability core
or
2) a low permeability core

(1-A) the magnet is very strongly attached to the high permeability core and almost all the domains of the core are aligned.  This will require a large input of energy to negate the attraction.  BUT, will the high permeability core more readily 'accept' the flux from the EM pulse meaning it will actually require LESS?

(2-A)  the magnet is attached, but not quite as much as a much smaller % of the domains of the core are aligned, thus less energy input to the EM to get it to drop.  BUT, will the core also be less 'accepting' to the EM pulse so it will require more input?

Or a small size core with a relatively large/strong magnet is going to fully saturate the core, so the high permeability core will require less.
But if the core is large with a relatively small/weak magnet this changes things?

Or what and why?

Tx

[Kator01]

Hi capthook,

that is exactly the question I have pondered on and I share your experience of mentally going in a loop on this for the last months´s.  One thing to consider is the spontaneous magnetisation which demands less energy, see here the topic "long range ordering" :

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Now as for a permanent magnet to trigger this allignement in an effective way, meaning not to over-energize
the core-material, there will be just on way to controll it : the air-gap-width. The air-gap if properly spaced will carry most of the energy and complete full saturation of the core.

I will carry this question to this guy from New-Zealand because he has build a special Adam-Aspden-motor.

Also of interest might be the Potter-Debate at Aspden´s Webpage here :

http://www.aspden.org/reports/Es4/esr4.htm

Hope it heps you.

Regards

Kator

[capthook]

Kator01-

Thanks for the link to the Potter-Debate paper.  I've downloaded it and will read soon.  Still haven't fully read the ENERGY SCIENCE REPORT NO. 1: POWER FROM MAGNETISM by HAROLD ASPDEN.

Also did a search of the hyperphysics site (seach term on google):
"long range ordering" site:hyperphysics.phy-astr.gsu.edu

gave me this page:
http://hyperphysics.phy-astr.gsu.edu/Hbase/Solids/ferro.html

Just basic information on ferromagnetism...

And the magnet is actually over a small airgap - was just easier to 'visualize' it as attached.

I would test numerous materials - but the high permeability materials are VERY expensive and VERY VERY hard to source (especially annealled).

As such, I'm still hoping that someone might give me a definitive answer.

tx

[Kator01]

Hi capthook,

in that hyperphysics-Link you have to read this "long range order" thingy.

http://hyperphysics.phy-astr.gsu.edu/Hbase/Solids/ferro.html#c2

Although I can not do the math I can tell you for sure that you can control the saturation-level in your em-core by variation of the air-gap. The bigger the distance ( air-gap) the less power you need for cancelling the allignement to the degree of setting the magnet free.
I am sure even this electronic engineer from New Zealand had just solved this by practical testing.
( variation of air-gap-width )
He was off for some holidays and I wiil contact him today and ask him about this problem. He may have some
working formulas.

Since most of the E-Mag is concentrated in the air-gap ( I have read a tutorial on switched-power-supplies ) you only need to expend that amount of energy to cancel the smaller energy-portion (saturation) in the core. Because you will not be able to cancel the emag in the air-gap in a direct way.

I will do a research on this but it might take some time, as I am a german and need to find relevant english literature.

Some days ago I put a file into the download-section : "E_mag-Fe-Air by Kator01", because there was the same topic which I had to draw the attention to in the Peripiteia-Thread.

http://www.overunity.com/index.php?action=tpmod;dl=0

I put together some  formulas and explanations from my old german physics-textbook dated 1940. Here in this book is a paragraph about the spark-inductor used at the end of the 19th century. Here it was clearly explained that E-mag in the air (and therefore the  fieldstrength H ) is thousands times bigger than in pure iron. Look at the formulas and you will see the relative permeability is in the denominator of the Energy-formula.
A similar situation occurs ( although not fully equivalent) when the magnet passes by the core at a distance.

Then as a repeater have a look at the file in the same section named "Permeability of pure iron".
Permeability is not a constant. It is depending on the fieldstrength. So you can engineer the point along this graph
where you have most efficiency as the permeability in decreasing at a certain fieldstrengh. It even can be brought down to 1.

Regards

Kator01