Any recommendations on coil/core geometry/dimensions?  Something like how a Brooks coil dimensions is proposed for an air core design?
Maximum width/depth of windings/ distance from core?
Core width/length? etc...

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Kator - I've tried to upload the Ebook to the uploads section of this site - but stated file size limit is 5meg and the Ebook is 12meg.  However - the link given before IS active and links to the .pdf download of the Ebook....

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Silicon Steel  (Electrical Steel)
 
"When low carbon steel is alloyed with small quantities of silicon, the added  volume resistivity helps to reduce eddy current losses in the core.  Silicon
steels are probably of the most use to designers of motion control products
where the additional cost is justified by the increased performance.  These
steels are available in an array of grades and thicknesses so that the material may be tailored for various applications.  The added silicon has a marked impact on the life of stamping tooling, and the surface insulation selected also affects die life.  Silicon steels are generally specified and selected on the basis of allowable core loss in watts/lb.

The grades are called out, in increasing order of core loss by M numbers,
such as M19, M27, M36 or M43, with each grade specifying a maximum  core loss.  (Note that this means that material can be substituted up , as M19 for M36, but not vice versa.) The higher M numbers (and thus higher core losses) are progressively lower cost, although only a few percent is saved with each step down in performance.  M19 is probably the most common grade for motion control products, as it offers nearly the lowest core loss in this class of material, with only a small cost impact, particularly in low to medium production quantities.
In addition to grade, there are a number of other decisions to make regarding silicon steels.  These are:

1. Semi vs. Fully processed material,
2. Annealing after stamping,
3. Material Thickness,
4. Surface insulation. 

  Fully processed material is simply material which has been annealed
to optimum properties at the steel mill.  Semi processed material always
requires annealing after stamping in order to remove excess carbon as well as to stress relieve.  The better grades of silicon steel are always supplied fully processed while semi processed is available only in grades M43 and worse.  The designer considering semi processed M43 should evaluate Low Carbon Steel which may provide equivalent performance at lower cost.

Even though annealed at the mill, fully processed material may require further stress relief anneal after stamping.  The stresses introduced during punching degrade the material properties around the edges of the lamination, and must be removed to obtain maximum performance.  This is
particularly true for parts with narrow sections, or where very high flux
density is required.  In one instance, a tachometer manufacturer was able to
reduce the stack height in his product by 10% by annealing after stamping.  The annealing cycle requires a temperature of 1350-1450 F in a non oxidizing, non carburizing atmosphere. Endothermic, nitrogen, and vacuum atmospheres all work well. The selection of lamination thickness is a fairly
straightforward trade off of core loss versus cost.  Thinner laminations exhibit lower losses (particularly as frequency increases), but thinner material is more expensive initially, and more laminations are required for a given stack height.  The most common thicknesses are .014 in., .0185 in., and .025 in. (29 Gauge, 26 Gauge, and 24 Gauge, respectively.)  These thicknesses are supplemented by thin electrical steels, available in .002, .004, and .007 in. thick.  Thin electrical steels are available in one grade (Equivalent to M19) and are made by re-rolling standard silicon steel.  Due to substantially higher material cost, thin electrical steel is used primarily for high performance and high frequency applications.  In order to gain full advantage from a laminated core, the laminations must be insulated from one another.  The simplest way to do this is to specify a surface insulation on the raw material.  Silicon steels are available with several types of insulation: 
--C-0:
Also called bare, or oxide coated.  This is a thin, tightly adherent oxide
coating put on the material at the steel mill, or during the annealing process
after stamping. This is the lowest cost insulation, but offers little
resistance.
--C-3:
Enamel or varnish coating which offers excellent insulation, but parts so
coated cannot be annealed after stamping.
--C-4:An inorganic coating providing higher resistance than C-0, but which will withstand annealing temperatures.
--C-5:
An improved inorganic coating similar to  C-4 but with significantly higher
resistance. It withstands annealing well in most cases.  This is probably the
best choice for most performance sensitive applications.  The main drawback to C-5 is  an increase in tool wear due to abrasiveness."
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Anyone have a source for ordering small quantities of electrical steel?

 Hi capthook,

thank you. I simply can not believe it how scattered information in the web is. But anyway look here,  even searched with google´s book-search-engine and could not find it.

Regards

Kator01

Huh - must be a US thing.
Google caused a bit of an uproar when they started the book scan project.  Royalties issues etc.
Just a week ago or so they settled a law suit for over $20 million relating to it.
Maybe it will clear some of the hurtles in the near future.

I upload the file to a free file service:

http://www.filepanda.com/file/vjdxk5ztmx4m/

It will take a min. or two (or more on dial-up - 12 MB) to download and then opens a .pdf window.
You can then click on "save a copy" in the top-left menu to save to your hard drive.

 

A 2nd Ebook of interest is:

Solenoids, Electromagnets & electromagnetic windings
423 pages, 7MB

A good complement to the first and written 25 later.
The author, Underhill, writes this in reference to the author of the 1st ebook link:

"The labors of Professor Silvanus P. Thompson in this field deserve recognition from the electrical profession, to which the author desires to add his personal acknowledgments."

The file is here:

http://www.filepanda.com/file/2rpkksms11kj/

1st attach picture:

A graph showing the results of different core materials using a small test coil as a generator coil.


2nd pic: MIG welding wire

Ran across this interesting core idea:

"Get yourself a roll of .030 MIG welding wire.

Make your coil form so that there is very little airspace at the center of the winding.

Wind the steel wire in tandem with the copper wire on the same form.

What you have there is an integrated, ultra-low eddy-current ferrous core.

You can also do this with regular mechanics wire. But, it's usually kinda dirty and oily right on the roll. MIG wire is nice and shiny."

What you lose in winding space for the copper wire because of the steel wire might be similiar to what you gain in being able to wind the coil to a smaller inner dimension?
Either way - an interesting idea I've never heard of!

Nice suggestion, any idea of the permeabilty of welding wire?  Btw, how is your electrical steel/ferrite projects progressing?  I received a 6" long/1" diameter ferrite rod from Stormwise.com.  It was encased in 1/8th thick plastic tubing for weatherproofing.  I chiseled off the plastic today and found two 3" segments pushed together end to end.  I wound one segment with 80' of 26 gauge wire.  When I went to test it, I found that my 9 volt battery was dead!  #%!&^$...very frustrating.  I'll have to get a battery and test it Saturday, will post the results then.

Hey capthook,

Ah, great idea. I like your random way of thinking. A side-effect with this idea is that you reduce the capacity between the windings as well. Some time ago member pese was speaking of a transformer-design
build in germany in the 50 ´s or 60 ´s. They used only iron-wire-windings and by this there was no need of a core because the permeability was built in - so to say.  Of course this design had heat-losses. But it would be intersting to rebouild such a transformer.

Another thing I found some time ago - and I was not sucessfull to find it in my files - but I rememer this :

They said - and this was backed by calculation and tests - that once a load ( weight ) drawn to the coil-core-surface and has come to rest and is in close contact - you can reduce the current to a certain percentage to hold it in place.
So you can try this with your test-rig you already have.

There is another effect where you could combine magnetic-attraction with electrostatic-attraction-forces to hold a load-weight in place if this is needed.By  this combination you can switch off your electromagnet and only have a few miliamps at 200 Volt DC left to to hold the load in place.
It is called Johnson-Rahbeck-Effect ( dicovered in 1920 ) I only have a german description and will provide this here but it will take some time as I have to scan this from an  old german physics-book ( 1940)  and translate it for you.

In the meanwile you can try to find it via different search-engines. One of my favorites is this one here :

http://clusty.com/search?input-form=clusty-simple&v%3Asources=webplus&query=

Best Regards

Kator01

@ CapnHook

No luck with the Ferrite.  A 3 inch core wound with 300 turns of wire and 1.5 amperes yielded 1/10th of a pound of force.  Essentially useless.  I'm going to query some manufacturers for some electric steel samples.  Hope I have better luck, next time.

Your weight/pull testing idea is a good one.  It's much easier and more accurate to pour water than my method with the nuts and washers.  It's time consuming to add some nuts, then remove a nut, add some washers, etc..
Thanks!!

What?!!?  Really?  DAMN!  It SEEMS it would make a great core.  I have a little piece laying around, and when I attach a magnet (large or small), the flux pours right through it like it was the magnet itself.

...............................
Good point. The effect of an air-gap is almost exponential.  So the smaller the airgap, the flux is x².  A close approximation is: half the pull for every 1/8" increase of airgap.  Of course it depends on the strength of the flux to begin with and the material being affected.

However - I wouldn't know how to design an circuit/process for automatically/accurately  adjusting the power draw to take advantage of this effect.  And in real time - it happens very quickly!
Or how to apply it to a pulse/repulsion style EM.

That small piece of ferrite you have, is it soft or hard?  The one that I ordered is soft.  Is the one you have already magnetized?  Could be I have a defective core.  Perhaps you'll have better luck with the Amidon material.    If you do I might try some.