Dual rotor axial flux motor design

[Miles]

Schiller design: http://schiller-energy.com/pdf/schiller-energy.pdf

Schiller patent:

[Miles]

ISIS YASA design: download/file.php?id=66703

ISIS patent:

[Miles]

You can get enamelled copper strip down to 1mm thick from Essex. See PDF

[rhitee05]

8mm x 1mm is pretty hefty stuff - comparable to 8-ga round wire. Bending radius could be an issue - you'd probably need to round the edges of the lam stack to accommodate it. Definitely suitable for a high-current motor, though...

If you want to provide me with some of the dimensions you're looking at, I can toss together a quick FEMM model as a place to start considering some of the tradeoffs.

[Miles]

8mm x 1mm is pretty hefty stuff - comparable to 8-ga round wire. Bending radius could be an issue - you'd probably need to round the edges of the lam stack to accommodate it. Definitely suitable for a high-current motor, though...

The insulation thickness values seemed quite high, too. But with only 3 turns x 2 .......

[Miles]

If you want to provide me with some of the dimensions you're looking at, I can toss together a quick FEMM model as a place to start considering some of the tradeoffs.

Thanks Eric. That would be very useful. I'll model up the stator modules properly for 12t and 18t layouts.

[Miles]

Reworked 18t stator:

[markobetti]

Reworked 18t stator:

will it be possible ti add this way one more lineup of magnets on top of allready mounted mags; for small increase in flux . If you remember ; the lynch motors have this option on their high power models . Modul per modul based motor..

[Miles]

Hi Marko,

I'm not up-to-date with what Lynch do so I'm not certain exactly what you mean.

This is a double rotor design and the second rotor is essential to complete the flux path.

If you mean stacking another layer of magnets on each rotor, I guess it's possible as long as it's allowed for in terms of space and rotor stiffness.

I've no plans to go into motor production....

[Miles]

This is what the present 18t stator looks like in relation to 20 rectangular magnets:

[Miles]

18t 16p:

[Thud]

When will you comit to making chips Miles?
This thread has my full attention..so far I like what i see.
my motor (s) langushes on a shelf...& I am almost out of Kudo's

[Miles]

Hi Todd,

I think I'll test out different construction techniques before I commit to a final design.

What do you think about the possibility of machining laminated blocks for the core modules?

How detrimental is minor bridging between the laminates at the edges, I wonder...?

[Thud]

Good question....
I would think the laminated block would be nearly impossible to machine conventionaly unless you actually held it under pressure in a vice or jig for the machining opperations....

My 1st though would be a grinding opperation (activly cooled) & some slow feed rates....depending on the lamination insulation material, I would think a quick clean up on a flat lapping table would be your best chance at elliminating any bridging between lams.

Just thinking outloud.

[Miles]

If one just machined the edges of the end sections it would be quite easy to lap them afterwards. A fully machined "I" section (from square blanks) would be more problematic, perhaps..

The laminations would be properly bonded (maybe pinned, too?) before machining.

[Miles]

Still wondering if there would be a significant advantage in using grain-oriented steel (up to 30% higher flux density but usually has a lower silicon content than non-oriented)?

Electrical steel references:

http://www.protolam.com/page3.html

[bearing]

Good stuff. Thanks for posting this

Most of the common electrical steels seems to be characterized at only 50-60Hz. In Sweden there is a plant making good electrical steel. Some if their steels (like NOxx) are characterized to 10kHz.

http://www.sura.se/Sura/hp_products.nsf ... A8002280E6
http://www.sura.se/

[Thud]

Miles:

Still wondering if there would be a significant advantage in using grain-oriented steel (up to 30% higher flux density but usually has a lower silicon content than non-oriented)?

I would like that answer from thouse in the know also.....I also have found sourcing reasonable amounts of any of the ellectrical steels has been problematic for me. especialy in a finer thickness like .2mm (.008") the prototype lam houses require a reasonable amount up front (1st born or just your imortal soul) & have no interest in supplying a small qty of material to a model maker.

I did buy a couple rolls of cheap 1080 low carbon steel shim stock in .008"t to try my hand at photo chemical machining. We'll go into more about that somewhere else.

I need to read through the PDF's you liked in a bit more detail when time permits.

[markobetti]

i dont see a point why not to make laminations : use 0.35mm or 0.2 mm soft silicone steel No. 250#.
winding wire perhaps : type(at least): Enameled wire, No. 2UEW, grade: F, internal resistance: 0.0087Ω

[markobetti]

http://www.villaindustrias.com/silicon-steel-info.html

[Miles]

i dont see a point why not to make laminations : use 0.35mm or 0.2 mm soft silicone steel No. 250#.
winding wire perhaps : type(at least): Enameled wire, No. 2UEW, grade: F, internal resistance: 0.0087Ω

I don't either Marko.

The idea here is to explore all the options. With most motor cores, it's not possible to take advantage of oriented steel. Here we have a segmented core with pretty much unidirectional flux paths. Is it worth trying oriented steel? I want to find out. It would also be pretty straightforward to use strip coils for the windings. Why not try that? It looks to give a significant advantage in fill factor.

Thanks for the link!

[Miles]

The thinnest Kapton tape is 64 micron of which 25 microns is the adhesive layer (40%!).

The technique used here looks interesting. Only 25 microns for the insulation! Pity that they only do it up to .005" copper thickness as a stock item

0.5mm copper thickness with the 0.025mm insulation thickness could give a fill factor of 0.8

[Miles]

This is where I am, at the moment.

There is a 1mm recess in the can which restrains the core modules in the axial direction. The collective wedging action against the core spacer strips (green) force the modules radially outwards, into the recess. I'm relying on the integrity of the lamination bonding and compression from the winding. I could also wind a layer of Kevlar yarn around the inner section of the core modules before epoxying them.

Will this be enough???

The coils will now be linked on the inside with circa 12 gauge wire, to avoid impeding the air flow.

[Miles]

Cross-section through stator:

[rhitee05]

Maybe something like an acrylic ring around the inner edge of the cores to keep them seated into the recesses?

If I understand the structure correctly, all of the torque reaction force is applied to those 1mm lips in which the cores sit? I'm not a materials or an ME guy, but that doesn't seem like a lot. On the other hand, this looks like a good arrangement to provide airflow over the coils and keep metal bits out of the magnetic path to avoid eddy losses.