Storing Cookies (See : http://ec.europa.eu/ipg/basics/legal/cookies/index_en.htm ) help us to bring you our services at overunity.com . If you use this website and our services you declare yourself okay with using cookies .More Infos here:
https://overunity.com/5553/privacy-policy/
If you do not agree with storing cookies, please LEAVE this website now. From the 25th of May 2018, every existing user has to accept the GDPR agreement at first login. If a user is unwilling to accept the GDPR, he should email us and request to erase his account. Many thanks for your understanding

User Menu

Custom Search

Author Topic: Magnet Core Solenoid?  (Read 19060 times)

arringtj

  • Newbie
  • *
  • Posts: 18
Magnet Core Solenoid?
« on: February 17, 2009, 06:24:35 PM »
EM guru question:

I am not building a PM Spiral / Sprain motor, but similar end magnet issue...
Given: Pole faces are 90 degrees to each other, not face to face... and magnet wire would be closer to other PM's than core.

If I have a 2 inch long X 1/2 inch diameter cylindrical N42 NDFEB magnet, can I surround it with a coil for the purpose of NEUTRALIZING it's field very briefly with a pulse of current???

Can the coil be "seen" by other PM's as the opposite polarity if current is opposite of core polarity?

What would a brief pulse of HF AC do in this coil?

Many thanks for any expert input!

Jeff

z.monkey

  • elite_member
  • Hero Member
  • ******
  • Posts: 1660
    • Scientilosopher's Domain
Re: Magnet Core Solenoid?
« Reply #1 on: February 17, 2009, 11:05:06 PM »
Modulate a permanent magnet field with a coil, been pondering that myself...

If the coil field is bucking the permanent magnet then it will reduce the flux.

If the coil field is aiding the permanent magnet then it will increase the flux.

If the coil field is alternating then you get both effects, alternating...

The poles of an electromagnet are determined by the magnetic right hand rule. 

http://hyperphysics.phy-astr.gsu.edu/Hbase/magnetic/magcur.html

It may take a little while to visualize this.  When you wrap the wire around the
inductor you should pay attention to the flow of electrons from negative to positive,
then apply the right hand rule to determine the flow of the flux on the core side
of the wire.  Then check your windings with a compass to be sure.  If you wind
the inductor backwards accidentally, then you can hook it up backwards relative
to the current source to reverse the flux.  Check this out to update your magnetic
fundamentals...

http://www.overunity.com/index.php?topic=6408.0

arringtj

  • Newbie
  • *
  • Posts: 18
Re: Magnet Core Solenoid?
« Reply #2 on: February 18, 2009, 04:25:51 PM »
Thank you , Z.Monkey!

Any one know what the fastest current rise config for the coil might be? The most efficient to "buck" the PM field?
Let's say I am mounting this 2 X .5 inch vertcally with the N end up. It is NDFEB N42
What gauge wire and how many turns around this 2 inch length?
What voltage/current?

I have 2 Dewalt 36 volt batteries (A123 Lithium inside ;) handy, by the way. 8)

Thanks,
Jeff

z.monkey

  • elite_member
  • Hero Member
  • ******
  • Posts: 1660
    • Scientilosopher's Domain
Re: Magnet Core Solenoid?
« Reply #3 on: February 18, 2009, 05:14:17 PM »
Howdy,

The formula for MMF (Magnetomotive Force) is basically Amps X Turns.

Amps being the keyword.  Use heavy gauge wire and fewer turns.

The permeability of the core also effects the magnetization.

I do not know what the permeability of a Neodymium-Iron-Boron magnet would be, probably better than Iron alone.

I use 1 layer of windings on a core, but you can add more layers if you like, increasing the resistance of the coil.  Using flat wire will increase the magnetization of the core.

If you want to use the batteries alone, just hook up the coil through a momentary switch.

If you want to give it an extra kick then hook up a large capacitor in parallel on the battery side of the switch.  When you punch the switch you'll get the extra current of the capacitor discharging through the coil.

There are many ways to do this, as a one shot or as an oscillator.

You could use a charge pump to generate a high voltage in a large capacitor and then discharge it through the coil.

This is where you get to experiment.  Build one then test it.  See how you can make it better, and build another...

TinselKoala

  • Hero Member
  • *****
  • Posts: 13958
Re: Magnet Core Solenoid?
« Reply #4 on: February 18, 2009, 09:05:15 PM »
"When you wrap the wire around the
inductor you should pay attention to the flow of electrons from negative to positive,
then apply the right hand rule to determine the flow of the flux on the core side
of the wire.  "



Doesn't the "right hand rule" refer to the direction of "conventional" current, not the flow of electrons? That is, we know that electrons flow from negative pole to positive pole, but aren't all the right-hand rules based on the mistaken direction, assigned by Ben Franklin, of "positive" current?

z.monkey

  • elite_member
  • Hero Member
  • ******
  • Posts: 1660
    • Scientilosopher's Domain
Re: Magnet Core Solenoid?
« Reply #5 on: February 18, 2009, 09:15:02 PM »
Well, you can test the theory by building an inductor, use the right hand rule to determine the north side of the electromagnet, and then test it with a compass.

I know that there is that disparity between electronic (- to +) flow and positronic (+ to -) flow...  After reading the Alchemical Manual I believe that there is a bidirectional flow happening, the particles (electrons) flow from negative to positive, and the holes (positrons) are flowing in the opposite direction from positive to negative.

A magnetic field also has a bidirectional flow, time field predominant forces are flowing in one direction and and space field predominant forces are flowing in the opposite direction.  Space Time Fields make the whole magnetism thing a lot easier to understand, thanks Aaity, and the Starfriends...

Ergo

  • Sr. Member
  • ****
  • Posts: 280
Re: Magnet Core Solenoid?
« Reply #6 on: February 18, 2009, 10:07:18 PM »
I do not know what the permeability of a Neodymium-Iron-Boron magnet would be, probably better than Iron alone.

The permeability of a Neodymium-Iron-Boron magnet is the same as air, namely 1.

It's not possible to alter the flux of a NdFeb magnet by a surrounding coil.
It would take an extremely heavy duty magnetizing force to affect the magnet.
But the heavy force would also demagnetize the ndFeb at the same time.

This idea is flawed and will not work.

arringtj

  • Newbie
  • *
  • Posts: 18
Re: Magnet Core Solenoid?
« Reply #7 on: February 18, 2009, 10:49:38 PM »
Thanks Ergo and everyone.

I understand that in the manufacture of NDFEBs they use large currents through large capacitors and dump them in a solenoid coil to align the moments.

So, I suppose I am describing the same, and it would demag if I meet or exceed the coercivity?
I thought this might be an issue, BUT...

What if the coil was 2 inches in diameter with .5 inch mag in center and my "gate" magnets on either side are now actually closer to coil than to NDFEB?

 ???

Best regards,
Jeff

z.monkey

  • elite_member
  • Hero Member
  • ******
  • Posts: 1660
    • Scientilosopher's Domain
Re: Magnet Core Solenoid?
« Reply #8 on: February 19, 2009, 02:51:32 AM »
Its worth a try...

You don't have to overpower the magnet...

You just have to get it to wiggle...

The fluctuation of the flux lines causes accretion of electrons...

Honk

  • Sr. Member
  • ****
  • Posts: 497
Re: Magnet Core Solenoid?
« Reply #9 on: February 19, 2009, 08:59:27 AM »
I agree with Ergo.
Myself I don't belive you can create enough force by your coil to affect the magnet.
The equipment used at the factory consist of a superconducting coil and a bank of
super strong and large capacitors that dumps their charge into the coil.
This creates a field of 10-20 teslas and it not possible to do is on your own.
But I also agree with z.monkey. It could be worth a try just for fun.
Don't forget to report you findings here at OU forum.

TechStuf

  • Hero Member
  • *****
  • Posts: 1280
    • Biblical Record Proves True
Re: Magnet Core Solenoid?
« Reply #10 on: February 19, 2009, 11:19:26 AM »

Quote
If I have a 2 inch long X 1/2 inch diameter cylindrical N42 NDFEB magnet, can I surround it with a coil for the purpose of NEUTRALIZING it's field very briefly with a pulse of current???

Arringtj, I happen to own a digital camera with an NdFeB flash catch which does just that....at least for the purpose of releasing the flash arm.  I also own a handful of the NdFeB magnets you mention and their fields can also be "neutralized" or more accurately, 'shunted', via similar method.

Ergo stated:

Quote
It's not possible to alter the flux of a NdFeb magnet by a surrounding coil.
It would take an extremely heavy duty magnetizing force to affect the magnet.
But the heavy force would also demagnetize the ndFeb at the same time.

This idea is flawed and will not work.


Said the parrot on the shoulder of the man with the tenured eye patch.  There are numerous methods by which to alter the path and density of the flux quanta surrounding an NdFeB magnet.  An EM coil is certainly one of those.


Why, just the other day I gingerly waved a piece of iron in the face of a mean, stubborn old Neo, and it got all bent out of shape....and that lowly piece of fickle ferrousness was hardly pulsating with heavy force at the time.


TS

khabe

  • Hero Member
  • *****
  • Posts: 525
Re: Magnet Core Solenoid?
« Reply #11 on: February 19, 2009, 03:05:18 PM »
I took apart today one car starter solenoid. Outer case was OD-52mm, ID-44mm
not welded tube and tried on the Lathe - very well machinable and looks like
Nickel contents. Sizes do not fit exact I need. Its very hard to find or ask if you
dont know exact type or mark of steel you need, or how its called ...
One possibility is to visit scrap store and perhaps find right size starter solenoid ..
... unfortunately Im little bid ill right now and my back causes pain as well >:(

Anyone has info about ???

With due respect,
khabe

z.monkey

  • elite_member
  • Hero Member
  • ******
  • Posts: 1660
    • Scientilosopher's Domain
Re: Magnet Core Solenoid?
« Reply #12 on: February 19, 2009, 05:15:36 PM »
I am building a solenoid based transformer now.

It is 2 inches long and about 0.85 inches in diameter.

It is the primary core for the Flapjack coil, here's the link...

http://www.overunity.com/index.php?topic=6640.0

It uses a soft iron tube and a 1/2" machine screw for the core.

After thinking about arringtj's idea I decided to make a second
primary coil with the NdFeB Magnets.  This web site sells some
0.75 inch ring magnets which I could stack up to make the core.

http://www.magcraft.com/products/ring/index.html

The rings are 1/4" tall so I stack up 8 and there is the NdFeB core.
I'll use a 3/8" machine screw to hold the core together and epoxy a
22 AWG winding to the outside diameter of the NdFeB magnets.

Thanks arringtj...

Edit:  The NdFeB ring magnets are 0.125 inches tall so I will need
16 of them to make a 2 inch stack.  At Magcraft's prices this is $27
plus shipping to make a 2.25 inch tall core.  That is pricey...

X00013

  • Hero Member
  • *****
  • Posts: 679
Re: Magnet Core Solenoid?
« Reply #13 on: February 20, 2009, 01:46:43 AM »
@ arring          as stated before, overcoming a neo with a wrap will be futile, i think what you might be looking for is somthing like this, take your .5 x 2 inch neo and place it end to end with same size isoferrite, then wrap the iso which has  low permabilty, the iso will flop poles via the neo and as you apply current to the wrap, only side effect will be they will fly apart when current is applied (simple enginnering problem),  hope this helps and good luck .

Low-Q

  • Hero Member
  • *****
  • Posts: 2847
Re: Magnet Core Solenoid?
« Reply #14 on: February 21, 2009, 04:01:34 PM »
EM guru question:

I am not building a PM Spiral / Sprain motor, but similar end magnet issue...
Given: Pole faces are 90 degrees to each other, not face to face... and magnet wire would be closer to other PM's than core.

If I have a 2 inch long X 1/2 inch diameter cylindrical N42 NDFEB magnet, can I surround it with a coil for the purpose of NEUTRALIZING it's field very briefly with a pulse of current???

Can the coil be "seen" by other PM's as the opposite polarity if current is opposite of core polarity?

What would a brief pulse of HF AC do in this coil?

Many thanks for any expert input!

Jeff

You can use a magnet as an electromagnet core. The difference is that the core this time has an magnetic offset. The energy you put in to the magnetwire will accordlingly reduce the total magnetic field of the magnet. However, the change in magnetic field is allways less than the energy you put in to the magnet wire. So if you want to make a OU magnetmotor based on magnet cores, you will probaly meet a dead end. But it's worth trying anyway for learning purpose.

Vidar