Dual Rotor and Casting Soft Magnetic Powders

[Wa]

hi,

my crude research with soft magnetic powders such as MPP and other nickel moly alloys leads  me to believe that it might be helpful to mix into the casting resin of a dual rotor stator - MPP, nickel-iron, and sendust are available in powder form

windstuff ed's casting projects would be a wonderful sort of testing for dual rotor or maybe even single rotor, depending on the permeability rating of the powder - there have been poured stators of iron powder (windstuff ed), but MPP and insulated nickel-iron powders have far less losses

i have experimented with chokes and toroids, and found improved saturation (obviuosly) over a simple air coil  - i have no way as yet to spin anything at speed, and current backflow

my question is; what happens at higher currents and rotor speeds? one poster uses sapphire powder to create strong magnetically inert stators, is this because at rpm and currents we would create magnetic lag with such stators using MPP? anybod tried it?

thanks,

wa

[JW]

Whoooa! Dude.

 I was mearly "suggesting the use" of saphire powder (aka AL02 or aluminum oxide)mixed in the resin epoxy or high temp epoxy ready mixes as provided as my preivious link.

 Its well known that wires suspended over a distance perform better because of cooling properties. This kind of performace is not generally seen with the same distance of wire wound into a coil. Then the coil is surrounded by an insulator such as fiberglass resin. Cystals on the other hand are semimetals, hence they will conduct heat like a metal, but yet wont conduct electricity that well. Glass is not the same, true cyrstals conduct heat much better than glass, and they have simular insulative properties. By aiding in the removal of heat from a stator you can get better performace from the wires and insolation on them.

 JW

[Ungrounded Lightning Rod]

my crude research with soft magnetic powders such as MPP and other nickel moly alloys leads  me to believe that it might be helpful to mix into the casting resin of a dua rotor stator - MPP, nickel-iron, and sendust are available in powder form

windstuff ed's casting projects would be a wonderful sort of testing for dual rotor or maybe even single rotor, depending on the permeability rating of the powder - there have been poured stators of iron powder (windstuff ed), but MPP and insulated nickel-iron powders have far less losses

Whoooa! Dude.

I was mearly "suggesting the use" of saphire powder (aka AL02 or aluminum oxide)mixed in the resin epoxy or high temp epoxy ready mixes as provided as my preivious link.

Nevertheless, Wa's suggestion makes EXCELENT sense.

You couldn't pot the whole thing in soft magnetic material, of course, because it would route the flux around the coils.  But you could mix up TWO batches of epoxy, one for the pole pieces with magnetic material, and one for the non-poles with sapphire or what-have-you.  Both would conduct heat.

You could use a temporary dam to shape the pole pieces in any way desired, allowing you do design the transitions to minimize cogging, then pull it out while the epoxy is still soft so the magnetic and non-magnetic portions bond to each other, forming a single mass.

The powdered magnetic materials are way better than laminations at limiting eddy current losses.  (That's why they're used in the inductors of switching regulators, where the magnetic fields are swapping around at kilohertz rates.)  If they're not prohibitively expensive they'd make dandy pole pieces to eliminate the large gap in the radial alternator designs.

They'd also be great for making the one-rotor, slotted-disk style.  Cast your slotted disk, insert your pre-wound coils, either pot them in with sapphire-etc-filled material or leave them open for ventilation.  (You could also do a second casting of the magnetic material to make the crossbars of T-shaped pole pieces after the wires are in place.

So the questions are:

 - Does anybody see anything wrong with the above speculations?

 - Where can we get this stuff?

 - How much does it cost?

 - Is there any special technique necessary for working it?

[Flux]

Anything that improves the thermal properties must be a good thing if it is not too expensive.

Also the magnetic stuff ought to be worthwhile even if it only has a modest permeability. It would be a non event for single phase, but that's just about a non event anyway.  For 3 phase the coging ought to even out,  and as you say it should be possible to shape things for best results.

Again it depends on the cost,I would  be interested in any results.

Flux

[windrules]

Hi guys, don't know if I should put this as a new post but I will start here.

Is it feasable to make the stator out of aluminium or stainless steel,say have one side cut to same shape as poured stator then put in spacers to wind coils around with say small plates on the other side.Been thinking of this all day and both of these metals are non magnetic and would heatsink rather well.The other thing is that you could rewind if need be to say thicher wire or more or less turns which to do with a poured stator you would have to start again.

The other thought I had was why don't you leave a hole in the center of each coil in a poured stator to allow more airflow. This could be done by iserting a piece of PVC tube or something in each coil.This should reduce the temp build up quite a bit.

Regards,

Mos

[Ungrounded Lightning Rod]

s it feasable to make the stator out of aluminium or stainless steel,say have one side cut to same shape as poured stator then put in spacers to wind coils around with say small plates on the other side.

Nope.  They're conductive.  You'd get eddy currents and they'd have to be laminated just like an iron flux path to prevent them from eating your energy and serving as a very strong electric brake.

Unfortunately, most things that conduct heat well also conduct electricity - because the moving electrons transfer vibration's momentum over a long distance as they take each multi-atom hop.  Without conduction electrons the vibration has to move from atom to atom, which takes longer.  (Some crystals with strong bonds are non-conductive but stiff enough that the vibrations travel rapidly.  Diamond and sapphire are two such.)

The other thought I had was why don't you leave a hole in the center of each coil in a poured stator to allow more airflow. This could be done by iserting a piece of PVC tube or something in each coil.This should reduce the temp build up quite a bit.

Yes, if you can get air circulation past it.

I've been thinking about only potting the part between the magnets and leaving the loops from one pass to another exposed to the air, protected only by the enamel - and spread them out a bit so air can pass through them.  The copper would conduct heat to the loops, where it would transfer easily to the air via the large surface area of the individual wires.

[Wa]

hi,

a few more leads on materials - my material science comes from a lifetime in the theatre as a propman in special effects - we cast everything, and solve problems with out of the box solutions,so... i am not a physicist, but i do have a background in machining ,casting and electrics - so take this info with a grain of salt...

the soft magnetic powders i have uncovered fall in roughly 3 catagories;

MPP - moly permalloy powder

High Flux, Genalex - Nickel-Iron high flux

Soft Magnetic Composites - Insulated Iron

these materials are meant to be compressed under very high pressure, then cooked for a time to flash off lubricants in the press process - i have found a scant few articles on the use of the powder in an epoxy pour as opposed to a heat cured pre-preg - i would imagine it is possible to get the powder in an insulated but dry state - unsure exact form factor, i will be speaking to different companies over the next week

MPP has relatively low flux density but almost no eddy current loss - it seems like it could work as an enhancement in a dual rotor genny  pour (pole area only) - no where near enough flux density for a single rotor machine

Soft Magnetic Composites (SMC) is basically irregularly shape iron particles insulated from each other - the material is already being used to make a variety of stators in many PM motors - very comparable to silicon laminates - the flux is 3 dimensional as opposed to linear to laminates - can we use this feature? - seems like SMC would work well in a single rotor genny, with a second pour to seal the slots - this material will cog, so  the best use of this material is to fill the slots and remaining voids with a second buttering of the material - there are also thermal advantages with sinking heat from the coils - this would be even more enhanced with a perimeter and interior pour of an aluminum epoxy around the coil ends (suggested earlier) - fins could be cast into the outer perimeter - in addition, the entire stator could be cast on top of an aluminum backplate for thermal bonding/conductivity

the nickel-iron high flux powders fall in-between, and i am unsure what there use would be - i will be obtaining samples of all these materials and welcome collaboration with application -

hope this helps,

warren

[Wa]

hi,

just to clarify, aluminum pour and aluminum backplate out of insulated aluminum powder (not plate) - they have that too -

also sapphire would be great (as previously discussed)

wa