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Author Topic: Winding a strong electromagnet  (Read 204289 times)

Xaverius

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Re: Winding a strong electromagnet
« Reply #120 on: December 11, 2008, 09:20:12 AM »
@ CapnHook,
             
                any luck with electrical steel?  My next step is to try Magnetic Metals, magmet.com...............

Honk

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Re: Winding a strong electromagnet
« Reply #121 on: December 22, 2008, 09:16:16 AM »
Hi all.

Just a small question.

I believe your'e going to pulse this electromagnets of yours.
Have you considered the influence of inductance while designing it?
This is of utmost importance if you want a fast response time, aka fast RPM:s.
You might want to keep the inductance below 50mH or less, if possible.
There is a trade of: Higher efficiency = Higher inductance = Slow current build-up = Slow electromagnet.

If you measure the inductance and resistance you can use this calculator to see
how long it will take to reach a certain current level (the desired amp-turns).
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indtra.html#c2
It has helped me out tremendously.

Xaverius

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Re: Winding a strong electromagnet
« Reply #122 on: December 22, 2008, 09:39:26 AM »
Hi all.

Just a small question.

I believe your'e going to pulse this electromagnets of yours.
Have you considered the influence of inductance while designing it?
This is of utmost importance if you want a fast response time, aka fast RPM:s.
You might want to keep the inductance below 50mH or less, if possible.
There is a trade of: Higher efficiency = Higher inductance = Slow current build-up = Slow electromagnet.

If you measure the inductance and resistance you can use this calculator to see
how long it will take to reach a certain current level (the desired amp-turns).
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indtra.html#c2
It has helped me out tremendously.

Yes, the higher the Inductance, the higher the reactance, and the lower the current and reduced Ampere-turns. Laminated steel and/or parallel-wired multiple coils should eliminate this problem.

Honk

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Re: Winding a strong electromagnet
« Reply #123 on: December 22, 2008, 09:16:04 PM »
My own findings does not show any way to eliminate the sluggishness of high inductance at high RPM:s.
A high inductance will force you to increase pulse voltage just to apply the charge time you desire.
The increased voltage x current = a lot more power. This is not comparable to static mode.
It's possible it'll work for you depending on the wanted RPM. I wish you the best of luck in your research.

capthook

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Re: Winding a strong electromagnet
« Reply #124 on: December 23, 2008, 04:41:25 AM »
An application specific question on electromagnet core:

An Adams motor design:
1. The rotor magnet is attracted to the EM core
2. Just before dead center, the EM is powered on just enough to NEGATE the attraction
3. The rotor/magnet travels past the EM due to inertia

How will the permeability of the core effect operation?  Or will it be the same no matter?

(a) the higher the permeability, the greater/sooner the attraction so the better the propulsion
(b) the higher the permeability, the greater the % of domains aligned by the rotor magnet, thus the greater power required by the EM to NEGATE the attraction.

So:
(c) No matter the core, (a) is relative to (b), so any core will be the same net result?
or
(d) a higher permeability core means NEGATING the attraction is easier/lower power?

http://www.surepure.com/view_product.php?prodnum=2192
$100 for 12" x .5"  99.6% pure iron rod
(non-annealed, cold-rolled, so don't even know how much better it might be without heat treating)
(and like 4x as much for 99.9%)

??

SkyWatcher123

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Re: Winding a strong electromagnet
« Reply #125 on: December 23, 2008, 11:58:22 AM »
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?

Xaverius

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Re: Winding a strong electromagnet
« Reply #126 on: December 23, 2008, 10:53:40 PM »
@ Honk:  more voltage would be needed to overcome high Inductance due to eddy currents.  These can be eliminated with steel laminations that are insulated from one another.

@ CapNHook:  both (c) and (d) are correct, although naturally you would desire higher permeabilty in order to use lower input power.

@ SkyHook: the voltage is maximum initiallly, then the current rises relatively slowly to the maximum value.

Kator01

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Re: Winding a strong electromagnet
« Reply #127 on: December 24, 2008, 12:53:53 AM »
Hi capthook,

it turns out a bit more complicated than just permeability and we have to study a bit more about some physical fact( this is also true for me ) I just received this info from an engineer in New Zealand who has constructed an Aspden/Adam-Motor which runs with some excess-energy but is not OU at this stage of development. He was refering to this website here for Aspen/Adam-patent on this motor:

http://www.angelfire.com/ak5/energy21/adamsmotor.htm

Move down to ELECTRICAL MOTOR-GENERATOR ( common patent by Mr. Aspden/Adams ).

Notice : this website is not related to the person I got the message from. He was refering to this website because  he wanted to show me the basis of his design ( Figure 6 and 7 )

But before you read this you should read in Aspeden´s website where the extra-power we all are looking for
is located and how to tap it. It is in the air-gap. And if you have higher permeabilty you will have stronger attraction-forces and need more EM-cancelling-power but you will have more power returned from the air-gap.
Permability can be controlled as it is no a constant along increasing values of  Ampere/windings ( see in the download-section here a document I place named "Permeability of pure iron" ). Have a look at the diagramm only.
Now Aspden talks in the Power from Magnetism of the operating-point below the knee of the B-H-Curve, which can be achieved by magentic-bias of the core-lamination.
May be you already know this topic. It is of utmost importance to fully understand this. Read it three times. I just
read it the second time and still have some problems especially if it comes to his calculations.

http://www.aspden.org/reports/Es1/esr1.htm

Regards

Kator01




Honk

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Re: Winding a strong electromagnet
« Reply #128 on: December 24, 2008, 11:57:27 AM »
@ Honk:  more voltage would be needed to overcome high Inductance due to eddy currents.
These can be eliminated with steel laminations that are insulated from one another.

Yes, higher voltage will accelerate any coil regardless of the inductance, just like higher
voltage will accelerate the charge of a capacitor, if there is no current limiting factor.
And the higher the inductance the higher the voltage, but eddy currents have very little
to do with this. The slugginess is always present in a high inductance coil/electromagnet
regardless of the core material. A core will only amplify flux and increase inductance.
Just use the link I provided. It will give you all the answers you need about coil pulsing.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indtra.html#c2
You just need to enter the Inductance, Resistance, Applied voltage and Pulse time.
This will calculate the achieved Current level at the specified Pulse time, aka Amp-Turns.
It can't be any simpler than that.
« Last Edit: December 24, 2008, 12:23:09 PM by Honk »

Honk

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Re: Winding a strong electromagnet
« Reply #129 on: December 25, 2008, 05:43:19 PM »
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?

When pulsing a coil the voltage will rise instantly (just as fast as you can apply it) but the current build-up is slow.
The higher the inductance the slower the build-up time. This is regardless of core material.
A ferromagnetic core amplifies the flux from the windings. And this process also increases inductance.
Ferromagnetic core amplification is named by Permeability. The higher the Permeability the greater the flux amplification.
The trade-off is higher inductance that slows down response time. Slow response = slow current build-up.
There is a middle way where the number of turns, aka amp-turns vs response time is the best combination.
This is totaly dependent on your needs in your own specific project. You'll just have to calculate, wind and measure
the outcome a lot of times. And then use this calculator to see if the amp-turns vs response time will do it for you.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indtra.html#c2

 

capthook

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Re: Winding a strong electromagnet
« Reply #130 on: January 08, 2009, 06:55:10 AM »
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

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Re: Winding a strong electromagnet
« Reply #131 on: January 08, 2009, 07:11:16 AM »
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

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Re: Winding a strong electromagnet
« Reply #132 on: January 08, 2009, 11:37:42 AM »
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

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Re: Winding a strong electromagnet
« Reply #133 on: January 08, 2009, 06:48:25 PM »
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

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Re: Winding a strong electromagnet
« Reply #134 on: January 08, 2009, 07:57:37 PM »
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