Winding a strong electromagnet

[TinselKoala]

@X: Picture hanging wire is generally steel (higher tensile strength) and is smaller in gauge or multi-stranded, here in North America. The soft iron wire is a general-purpose stuff usually sold in fairly large rolls (several pounds?) and is used for fencing, baling hay, concrete rebar tieing, anything you need a stout but formable wire for. I see that it is also called black iron wire.
When using it for cores it can be left bare, insulated with varnish, heat shrink, or any combo. You can also experiment with using the core itself as part of the circuitry, in whole or in part. Pack it tight, or even embed it in epoxy, to keep things from vibrating under AC stimulation.

EDIT to add there's a trade-off between number of turns and the added inductance. It isn't just resistance of the windings that is of concern. So there is an optimum number of turns, wire gauge, etc. for a particular core geometry and purpose (motor, transformer, choke, etc.) Electric motors and generators are remarkably efficient already and more efficiency would be a very strong sales incentive. IF motors could really be improved by reducing wire size and adding turns, beyond what has already been done, even just a little bit, it would be big news. Joe Newman's motors are remarkably inefficient flywheel energy storage systems; the main benefit from all that wire is the rotating mass it provides for the flywheel.

[capthook]

@ CaptHook, how is it going.  I can totally relate to your frustration on finding high permeabilty materials.  I'm not sure about cold rolled steel?  Could you provide more information about it?  The permeabilty is most important....
I think the best material is silicon electrical steel which is very common but manufacturers will only sell to buyers with LARGE orders.  If you can salvage the cores from used transformers or inductors you could obtain the material, but I'm not sure how to do this.

think the best material is silicon electrical steel which is very common but manufacturers will only sell to buyers with LARGE orders.  If you can salvage the cores from used transformers or inductors you could obtain the material, but I'm not sure how to do this.

Cold rolled steel:
http://www.ussteel.com/corp/sheet/cr/mls.htm
http://www.coilgun.info/theorymath/home.htm
Maximum permeability: 2,000u

Silicon electrical steel:  I second your motion and also wonder where to source a small, inexpensive, rod shaped piece !?!?

[Xaverius]

@X: Picture hanging wire is generally steel (higher tensile strength) and is smaller in gauge or multi-stranded, here in North America. The soft iron wire is a general-purpose stuff usually sold in fairly large rolls (several pounds?) and is used for fencing, baling hay, concrete rebar tieing, anything you need a stout but formable wire for. I see that it is also called black iron wire.
When using it for cores it can be left bare, insulated with varnish, heat shrink, or any combo. You can also experiment with using the core itself as part of the circuitry, in whole or in part. Pack it tight, or even embed it in epoxy, to keep things from vibrating under AC stimulation.

EDIT to add there's a trade-off between number of turns and the added inductance. It isn't just resistance of the windings that is of concern. So there is an optimum number of turns, wire gauge, etc. for a particular core geometry and purpose (motor, transformer, choke, etc.) Electric motors and generators are remarkably efficient already and more efficiency would be a very strong sales incentive. IF motors could really be improved by reducing wire size and adding turns, beyond what has already been done, even just a little bit, it would be big news. Joe Newman's motors are remarkably inefficient flywheel energy storage systems; the main benefit from all that wire is the rotating mass it provides for the flywheel.

Hi, I have a lot of picture hanging wire here in my gallery.  I am familiar with baling wire, rebar wire, etc. so now I know what to look for.  I hope it is more permeable than ordinary hardware(nails, screws, bolts).  Enamel spray paint would be my insulator of choice with wire bundles to reduce eddy currents and Reactance.

You're right, motors are now extremely efficient, approaching 100% in most cases.  This has to do primarily with rising electricity prices  and using motors in small places such as electric razors, cd drives etc.  In my experience there are already some small motors(primarily DC) that are overunity.  For a given amount of electrical input, the mechanical output is greater.  What is very frustrating is that most small motors don't give their rated output, but if you search Data Sheets for small motors you can sometimes find the information.  The larger motors, used for compressors, pumps, etc. usually have a horsepower rating but I've never found any that are overunity.  It seems the larger the motor,  the less efficient but the greater output in absolute terms.

[Xaverius]

Cold rolled steel:
http://www.ussteel.com/corp/sheet/cr/mls.htm
http://www.coilgun.info/theorymath/home.htm
Maximum permeability: 2,000u

Silicon electrical steel:  I second your motion and also wonder where to source a small, inexpensive, rod shaped piece !?!?

I see cold rolled is the same as silicon electrical.  Like I say you can salvage core material from used motors and transformers, but obtaining the right size might be difficult because these cores are machined to a particular shape.  Also have you tried ScientificAlloy.net?  You'll have to telephone them before 5:00 P.M central time and talk to a salesman.  They quoted me $250.00 for pure iron, ask them about EM core material.

[mondrasek]

I know this might step off topic, but I've got to ask...

Say you are to make an electromagnet where you use a great number of single turn conductors wired in parallel.  Does this create an EM with nearly zero resistance, reactance, and impedance?  What kind of capacitance would such a device have compared to one of an equal number of turns wound from only one continuous conductor?

M.