IRON FILINGS in Epoxy for stator?

[xymox]

Was thinking of a way to make a stator without laminates. This would be used in a 3 phase single rotor alternator, much like an induction motor conversion that I see here on the site.

I was considering using expoxy and mix with a large amount of iron filings to surround my coils and by doing so would surround the coils with the iron creating an efficient flux path. In effect I would be pouring on the epoxy/iron mix directly on the coils/stator and rotating at high speed to evenly distribute the mix.

Any problems with this?

[xymox]

For some reason my post is not staying after I hit submit. Anybody care to elaborate?

Regards,

[kurt]

i think Tomw was thinking you were meaning iron filings inside the stator of a duel rotor if you are then forget it.

if you mean a single rotor with a laminate stator backing like i think you do. then casting the stator backing using iron filings/powder and resin will work. windstuff ed did one that way.

http://www.windstuffnow.com/main/poured_stator.htm

you will have iron loss and possibly cogging depending how you build it that you do not have to deal with with a duel rotor but it is possible to make a functional alternator that way.  

[Flux]

There is no doubt that you could get some sort of result using iron filings in some sort of resin. At best it is not likely to be very good, there seems to be good reasons why this has never been adopted by any motor or generator manufacturer.

I suspect there is a fairly critical concentration of filings beyond which it becomes sufficiently conducting to have eddy current losses as a serious issue, At low concentrations the flux path will be very poor.

After about 150 hears of development there seems little chance that these ideas are new and they haven't stood the test of time. Sometimes changes in technology make old ideas practical but now that neo has made the air gap alternator a practical proposition I see little hope for half baked iron cores but don't let me stop you trying something different.

Flux

[bob g]

being the Bob from Windstuff's page, i know a bit about castiron resin mixes

a couple of thoughts if i may

1. the permeability is not good, better than air but much less than laminate silicon steel.
   
2. the stuff is very high in electrical resistance so eddy currents should be small.
   
   

turns out it is ok for single magnet rotor where you need an opposing steel to return the flux from the magnets, just ok,, easier than making a sloted laminate backplate, but not near as good, now having said that.

i don't know of anyone that has worked with this stuff in a dual rotor air core alternator, it might be that there is some potential in that the stuff would provide some directionalilty across the airgap without most of the attendant cogging issues that laminate steel presents.

if it weren't so damn costly in time and money one could use the polymer cast iron

to make up the centers of the coils, much like coil formers. wind the coils on them

screw them down to a wood backing (bottom of the form) and then imbed the coils into the common resin mix.

there likely would be some improvment in output from the aircore alternator using this method, perhaps more than what is given up due to cogging.

again there would be some cogging but only a fraction of that presented by laminate steel.

if someone wants to go that route, a good source of cast iron chip is under a brake lathe,, just use a magnet to winnow out the good iron from the dirt.

when it comes to mixing with resin, mix the resin with its hardener as usual

and then fold it into a plastic container that has the needed amount of castiron chip in it waiting. use no more than is needed to make it a wet mix, very stiff and almost dry works very well.

there are a jillion other uses for this stuff as well, it makes a very good cold cast iron, and with the addition of a steel frame armature (much like rebar in concrete) very strong casting can be made.

bob g

[bob g]

i would like to make a few more observations

1. the polymer castiron mix as another interesting  property that might make it useful

to the aircore machines, that is its ability to be very wear resistant.

should one use it to fill the centers of the coils as described and at some point the magnet rotors started to make contact with the core, they would harmlessly glide over the polymer cast for quite sometime before getting into the copper.

2. the use of polymer cast iron would make a fairly drastic reduction in the airgap of an aircore machine, even with the lower than steel permeability of the material it still has much higher permeability than does air.
   
3. the stuff should aid in focusing the flux more effectively across the poles most especially at higher amperage levels where amps in the stator wire work to distort the fluxpath as the current increases. far easier to distort a fairly wide flux path that has nothing but air in it, would seem to me.
   
   

my point is, there may very well be some benefit to using polymer cast iron

perhaps a bit more discussion and theorizing is in order if not experimentation?

bob g

[BigBreaker]

Yes but then you have to deal with cogging.  The rotors want to center the magnets on the cores and that makes the whole generator resist start-up.

[bob g]

you will definetly have some cogging, but no where near as much as you would with

a laminate steel core

my experiments lead me to believe that the polymer castiron lies somewhere between  zero cogging of an air core and hard cogging of a steel core.

what has not been proven to me at least is whether the gains from reduction of airgap distance and a more focused magnetic field offsets whatever is lost from cogging.

my thinking the gains would possibly offset what is lost due to cogging in all but the smallest of applications, in low wind areas. larger units in reasonable wind area's likely would not have an issue with the low amount of cogging.

bob g