Magnet Core Solenoid?

[arringtj]

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]

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]

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.

Thanks,
Jeff

[z.monkey]

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]

"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?