Winding a strong electromagnet

[capthook]

the AT/W ratio is the same @ 10.

Xaverius - thanks so much for the clarification!  I had been scratching my head the last few days over that.

As TK points out - fewer turns of thicker wire reduces resistance and increases amps that increases EM strength at the cost of more power consumed.
Winding 2-in-hand further reduces resistance and increases amps that increases strength at the cost of more power consumed.
Two excellent methods for increasing AT per meter.

However, if the goal is OU, the more power you consume the more power you must produce.  Catch-22.
This has been the reason for my focus on the AT/watt.
You may have noticed on my excel spreadsheet the power input of .5 watts.

The last wind I did was:
#22 AWG : 140' : 3/8" x 3" core : 1" OD  x 1 7/8" L coil : 781 turns : 2.3 ohms
1.06V x .461A = .488W : 360 AT : 1/2 lb. of holding power.

So with under 1/2 watt of input, I'm getting what appears to be a sufficient EM strength for my application.
However, thanks to the discussion here, winding it 2-in-hand will increase the EM strength relative to the power draw.  (ie. 50% more power but 75% more strength -)  The same AT/W but a relative larger flux - a larger % of domains aligned.
As such, designing for larger device output to accommodate the larger EM power draw should result in a net system gain.

Another thing I noticed this last week:
A larger core diameter will perform poorly over a smaller diameter at low input power.
The 3/8" core works better at .5W than the 1/2" core.
My thinking is that the low input can only align a small % of domains.
With a smaller core, that % of alignment is greater than the % of the larger core meaning greater EM strength.

[capthook]

What about 'flux focusing'?  Focusing the flux into a small area transmitted over an airgap.

What methods might be used?  How effective might it be?

Something like the attached picture....

[Xaverius]

Hi CapNHook,

               Sorry for making you scratch your head so much, my technical writing skills are not the best in the world but I'm getting better day by day, LOL!
Also, the math as you can see will sometimes throw you off.  I've been working with electronics and physics for many years and I can easilty get confused when the numbers start flowing, which they most certainly will with these two topics, LOL!

                 That being said, you made a good observation with regard to low power input and a narrow cross-sectional core.  I think you're right, at low power less domains are capable of alignment, also I might note that the same thing happens with shorter cores.  I've had the experience that at low power inputs, shorter cores yield less magnetic force, probably because the domains are squeezed together longitudinally and can't align efficiently.  In other words, a longer core allows the domains to "stretch" lengthwise and align properly.

                  One thing you may know by now, when you DOUBLE the magnetic field strength(H), you QUADRUPLE the magnetic force.  So in your examples, when you DOUBLE the AMPERAGE, you also DOUBLE the WATTAGE, however the AT/W remains the SAME, but the MAGNETIC FORCE QUADRUPLES.

                   In your application you are using repulsion, in mine I am using attraction.  If BOTH modes are used with a pulsating DC power source you are effectively DOUBLING your output.  Attraction and repulsion are used in AC motors, but to no overunity effect because when the cycle changes directions the attraction or repulsion is negated gradually.  With pulsating DC that problem is eliminated.  Also if you use BOTH POLES of the EM you double your output again.  Double the amperage, double the modes(attraction/repulsion), double the poles(N/S), you will increase your output by 16X.

                    BTW, have you achieved any result with 1006?  Good luck.

[Xaverius]

What about 'flux focusing'?  Focusing the flux into a small area transmitted over an airgap.

What methods might be used?  How effective might it be?

Something like the attached picture....

Flux focusing would indeed prevent most leakage and increase efficiency.  I'm not sure how it would be done other than alternate stator poles with opposite polar(N/S) EMs in close proximity.  You might look into Joe Flynn's technology or the Hildenbrand valve on Peswiki, if you haven't already.  They might give you a clue toward flux "steering".

[capthook]

Thought I would add this here as equations can get lost in the shuffle and might not be easily 'translated':

Question: I want to duplicate the 2000 Gauss strength in an electromagnet with a 3/4 inch diameter, 2 inch length solid metal core.

Answer:
A rough approximation:

(1) H in Oersted= (.4 x 3.14 x N x I)/coil length in cm

(2) B in Gauss = (H x (core permeability x 0.00000125664)) x 10000

So if 2,000 Gauss needed with core permeability of 800u:

H= 2000/10.05312 = 199
(rearrangement of  (2))

H = (.4 x 3.14 x N x I) / 5.08 = 199

N x I = (199 x 5.08) / 1.256 = 805 ampturns

So you could use:

N x I = 805 turns x 1 amp = 805 ampturns

805 turns of #22 AWG = 8.3 ohms
I=V/R : 9volts / 8.3 ohms ~ 1

So 805 turns of #22 AWG at 9 volts on a 800u permeability core (1010 steel) will achieve a rough approximation of around 2000 Gauss.