APL's DIY axial-flux motor

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fechter   100 GW

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Re: APL's DIY axial-flux motor

Post by fechter » Apr 25 2020 10:43am

The anodizing looks great! Nicer than a lot of factory motors. Great to see thing moving forward.
"One test is worth a thousand opinions"

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Re: APL's DIY axial-flux motor

Post by APL » Apr 26 2020 2:35pm

Thanks! I've got my fingers crossed. I'll have to get moving on it's sister project,.. installing a bigger battery, so I can
properly abuse it when the time comes. The little Dewalts are just going to tickle it.

I inherited a lithium give-away a while back, from a local scooter importer that gets battery returns,.. mostly bad BMS's.
He didn't want the fire hazard, and now I have the same problem. But theres a few of them that look like they can be
shoe-horned into my battery space, and just about double the output.

Meanwhile, I started designing the fan segments for this motor. I'll have to sneak up on it by printing singles, until I
get it to fit just right, and even then I have to wait until the spacers are finish-milled for the air gaps before I can do
the final prints.
Outer Fan Segment..png
Outer Fan Segment..png (98.17 KiB) Viewed 1226 times
Amberwolf your project looks great, an awesome idea! Lebowski brain in a massive Honda body,.. sounds like a movie
I saw once, Franken-something...? Can't wait to see it taking shape! Bulletproof, with all the bells and whistles! :thumb:

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Re: APL's DIY axial-flux motor

Post by Dui, ni shuo de dui » Apr 26 2020 8:56pm

APL wrote:
Apr 26 2020 2:35pm
Meanwhile, I started designing the fan segments for this motor. I'll have to sneak up on it by printing singles, until I
get it to fit just right, and even then I have to wait until the spacers are finish-milled for the air gaps before I can do
the final prints.
That's so great to finally see your motor being built, it looks really awesome!

For the blades, I suggest to curve them the other way, just like they are in almost all centrifugal fans. I'm no expert, but I think that the way you designed them right now will be noisier and much less efficient, because it will change the natural direction of the air coming out of the motor, for no actual purpose.

Here is what I'm talking about:
Untitled.png
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:bolt: :bolt: My electric Ninja 250 clone: 16 000W 72V40Ah A123 cells : :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=90032

:bolt: :bolt: My electric Scooter: 11 000W 72V 50Ah LiFePO4 cells: :bolt: :bolt:
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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Apr 26 2020 9:29pm

Maybe were seeing it different, I'll show the direction it should be going. I thought it should help scoop it out. But maybe
your saying that they should still bend the other way, to be quieter?
Outer Fan Segment. copy.png
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serious_sam   1 kW

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Re: APL's DIY axial-flux motor

Post by serious_sam » Apr 26 2020 10:23pm

Dui, ni shuo de dui is correct. The curvature should be reversed.


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Re: APL's DIY axial-flux motor

Post by APL » Apr 27 2020 12:57pm

Thanks for the help! :thumb: I see my blunder now. Theres a flaw in my ointment. :)

Looks like the blade should actually be an air foil design, but I suppose for production purposes they usually use a piece of
curved tin, making it a forward curved blade.
Centrigugal blade design..jpg
Centrigugal blade design..jpg (39.45 KiB) Viewed 1167 times
Evidently, they will all work, forward, backward, or even straight radial,.. but noise an efficiency will suffer. It depends
on the speed and the application. Forward curved is most efficient though.

Well, since it's being 3D printed, I can try to do an air foil style without to much trouble, or just curve it the other way.
I'll print this one up, to check the fit, and make the changes on the next one.

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Re: APL's DIY axial-flux motor

Post by fechter » Apr 27 2020 4:55pm

Since the motor RPM is quite low I don't think the curvature will matter much. Wind from the forward speed will have a bigger effect.
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Re: APL's DIY axial-flux motor

Post by APL » May 04 2020 1:26pm

I got the first print back, just a course print for sizing, and find that it's about 2mm to long. The spacers form a slanted
hole, (trapezoid), so it's a little hard to measure. Thought I'd be closer than that though. :confused:

Well, no matter, I'll redesign with the correct blade curve, and try again, that's the beauty of 3D printing. I have to thank
you guys for getting me into Cad., it's one of the coolest things ever! :)
IMG_2285 (1) copy.jpg
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Re: APL's DIY axial-flux motor

Post by APL » May 08 2020 8:21pm

I got a package from Texas today,.. Coleasterling has shipped the SMC cores.  One look inside took my breath away, he
has worked his magic on the raw slugs that I sent, and turned them into metal jewelry!  Those CNC machines of his,
make my 50's Cincinnati mill look like a hand drill!
Beautiful machining, and really puts a suit and tie on this motor build.  I'm back to thinking that this material might be
usable yet. Much tanks, and thumbs up to Coleasterling & crew! :thumb:
2 Cores..jpg
2 Cores..jpg (119.12 KiB) Viewed 927 times
Curious about the weight of these new cores, I put them on the digital scale and came up with 2920 grams for all 36 of
them, or 6.43 lbs. At roughly 6-1/2 lbs, they're only about 2 lbs heavier than the last cores, and there were only 21
of them.

So thats real good news weight-wise, and I'm sure that I can hone some more weight off of them, once we figure out
what a minimum amount of core steel is necessary. For now, this is a good starting place, and will give a good base line.

I have to lengthen the slots in the stator carrier, to match the longer slots on the cores when they were redesigned for
external end windings. And I suspect that I'll have to relive the spacers and fan blades a bit, to make room for the copper,
since it will be outboard a little more.

At any rate, winding the coils is coming up at last,.. and the big road test will be soon after. 

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Re: APL's DIY axial-flux motor

Post by fechter » May 09 2020 11:03am

Those are beautiful.

I forget, why did you not use a brim on the end turn area? From what I read before, that's a way to reduce copper losses and weight.
"One test is worth a thousand opinions"

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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » May 09 2020 2:39pm

Yes, I'm being torn between the open end turn, and brim theories. One day I'm this way, and another day I'm that. At the
moment I'm with you, I should have left the brims. It will work both ways though, and I might still have the option to
machine the brims later. Rather than change my mind too many times, I put my foot down and made the choice.
It does allow for more flux transfer through the stator carrier though.

As the theory goes, (if you can call it that), only radial, or slot turns create torque. But where this saying came from is
not clear to me, and I've noticed people tend to repeat things without really understanding them.

Certainly it is true with air core windings, and probably true with long radial motor armatures with long slots, and loose
end turns, (which are historically the most common), but I question the application to smaller trapezoid or squarish cores.

I'm currently of the opinion that any copper tight up against the steel is going to contribute Lorentz force into the core,
ultimately creating a stronger north and south pole., which is all the PM's see anyways. The pole face, not the turns.

The fact that the brim is there to specifically keep the PM's from interacting with the copper should be proof. But theres
also the fact that if one uses a 'C' core in a motor, the windings are no where near the core faces, and can't have anything
to do with torque other than Lorentz transfer through the steel to the pole face.
C cores.jpg
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At any rate, were still in the ball park, and in an effort to reduce weight, I'm voting for brim's, and anything else that will
lose weight. My secret goal is to home build a 10 lb. 2K watt motor, but it's probably pretty lofty. One step at a time. :)

For now, I'll wind these up and check it out,.. I'm getting anxious to see it spin. It would be a good test to try the brims
next, and see what the difference in performance and weight might be. I suspect that these cores might have too much
steel in them anyway.

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Re: APL's DIY axial-flux motor

Post by fechter » May 10 2020 12:03am

It probably won't make a really noticeable difference. Having more mechanical strength has a lot of advantages too. Motor design is all a bunch of trade-offs.
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Re: APL's DIY axial-flux motor

Post by coleasterling » May 11 2020 11:46am

Looks awesome! Thanks for taking such good photos and thanks for the compliments!

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Re: APL's DIY axial-flux motor

Post by major » May 11 2020 10:46pm

APL wrote:
May 09 2020 2:39pm
...
also the fact that if one uses a 'C' core in a motor, the windings are no where near the core faces, and can't have anything
to do with torque other than Lorentz transfer through the steel to the pole face.

C cores.jpg
...
Hi APL,

Could you elaborate on Lorentz transfer for this geometry? Perhaps do a visual aid showing the directions of flux, current and force. Thanks.

major

PS. Also it appears that 3/4 of the copper would be end-turn.

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Re: APL's DIY axial-flux motor

Post by Dui, ni shuo de dui » May 11 2020 11:00pm

Looks amazing, again wonderful work!
Can't wait to see it finished and running!!!
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Re: APL's DIY axial-flux motor

Post by APL » May 12 2020 2:19pm

Major,.. should be the same as a single loop coil, where all the force goes in the same direction. Basically a simple coil
and core, except bent. Flux concentrations in the air gap are shifted to one side because of the difference between in
lengths between the outside and inside diameters of the 'C' shape.

I can't find anything but side views of these things, but heres a link to Images of others; https://www.google.com/search?q=flux+ga ... 1665&hl=en
1mm_flux_gap_round.jpg
1mm_flux_gap_round.jpg (18.4 KiB) Viewed 704 times
Taken from Things in motion; https://things-in-motion.blogspot.com/2 ... motor.html

I guess what I'm saying is that if the coil is far enough away from the core ends, that the side of the core the windings
are on should be irrelevant. They all contribute equally to the core end flux, and that only the shape of the core face,
width/hight, will make the difference.

It might be misleading to say slot windings contribute to torque, it should be core shape or side length contribute most,
same thing, but a different way. :?:

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Re: APL's DIY axial-flux motor

Post by major » May 12 2020 3:39pm

Thanks for the reply APL. But what I am interested in is how Lorentz force law is applied to this geometry. Namely the flux, current and force vector directions. Looks to me like the current and force ( or motion, tangential to rotor) are in common direction which doesn't work well with the required orthogonal Lorentz relationship. Also the 3/4 end-turn coil seems poor choice. Have you, or anyone, seen a real-life motor example?

Thanks again,

major

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Re: APL's DIY axial-flux motor

Post by APL » May 12 2020 8:33pm

Sorry for being basic, and misunderstanding. I've seen these motors in my searches from time to time, but always thought
that it was a dumb idea to have coils in the diameter, as it makes the motor to large, and the extra steel in the C-core is
not a good idea either, so I have always passed them by.

Looking around for them now is not bringing up any 'actual' motors, only papers, and most of what I find is in the switched
reluctance field. Evidently the C core is attractive for stability, and noise for that design.

Anyway, heres a good paper on the C-core motor above, and has a lot of good info and graphics on that SRM.
https://www.motor-design.com/wp-content ... switch.pdf

Otherwise, theres a Semantic Scholar paper on another similar SRM, but that requires a sign in. The graphics are accessible though. https://www.semanticscholar.org/paper/A ... 5d2800ef62

Sorry, no real motors yet,.. but I'm probably not using the correct term for the search.
Another C core..jpg
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Re: APL's DIY axial-flux motor

Post by major » May 12 2020 10:42pm

Hi APL,
That second link is about SRM. You can view the diagrams without sign in. This one did have vectors.
Has 15 C-cores/coils and rotor with 12 steel blocks on the periphery. From your post showing a 12 C-cores, I thought those were PMs.
2-Figure2-1.png
SRM
2-Figure2-1.png (312.49 KiB) Viewed 673 times
An interesting oddity but not much good for a PM motor unless I'm missing something.

major

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Re: APL's DIY axial-flux motor

Post by APL » May 13 2020 12:59pm

Being a newbie to motor world, I've just become aware of reluctance motors, so I don't have much to say about them.
They are very interesting though, and I'm all for tossing out the PM's. There seems to be a startup direction problem,
but I would think that a set of Hall's and a go/no-go circuit would help. The most attractive part, is the supposed lighter
weight potential that they claim, but all the radial designs I've seen so far appear to have a lot more iron in them.

I'm seeing a fairly good selection of axial SRM's, and perhaps that design has a better weight potential. I wouldn't mind
trying something like that, but it will have to wait until I have a better understanding of SRM motors.
At the moment I'm still struggling with getting a 3 phase PM motor off the ground. :)

Thanks for your input, and graphics, it helps in understanding this machine. I'm not sure about their power potential,
but since there are no PM's, I would think that it's just a matter of how much current you can put into it without over
heating,.. and so the cooling of these things becomes crucial.

The Semantic Scholar link is about a 5 phase axial,.. 5??? Good luck finding a controller! I should probably try signing in
to that account though, because it is plum full of the most interesting papers!

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Re: APL's DIY axial-flux motor

Post by Lebowski » May 13 2020 1:41pm

You can run a SRM sensorless from start with full torque... the tech is what I uploaded here on ES. With a SRM everything is based on the wire inductances varying a lot with the rotor angle.
The most difficult bit about a 5 phase controller is finding the appropriate micro processor, one that has 5 sets of PWM outputs. The math is the same as for 3 phases, just with Clark and inverse Clarke for 5 phases instead of 3. Rest is the same.

All simple and doable, just lots of work...

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Re: APL's DIY axial-flux motor

Post by madin88 » May 14 2020 5:12am

fechter wrote:
May 09 2020 11:03am
Those are beautiful.

I forget, why did you not use a brim on the end turn area? From what I read before, that's a way to reduce copper losses and weight.
https://things-in-motion.blogspot.com/2 ... orque.html

from chapter 2:
"End turns in air-core motor designs are not considered in the calculation of torque as they are either outside of the region exposed to the permanent magnet's magnetic field or the force generated is in the wrong direction."

same is true for iron core motors

"In my next post, the concept of flux linkage will be explored and used to understand why end turns still do not contribute to flux in conventional iron-core motors."

I think this aplies to most motors which have surface mounted magnets or better say any motor which doesn't have potential for reluctance torque (like IPM motors have).

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Re: APL's DIY axial-flux motor

Post by APL » May 14 2020 10:00pm

I didn't see his "next post". :?: I'm probably missing something really basic, it's easy to find info on complicated things,
but the super simple stuff is rushed over, and if you don't get the very basics, then everything else will suffer.
I'll show a couple of simplistic thoughts I have, and maybe you can tell me where I'm getting things wrong.

If we take a single coil loop, we can see the magnetic field is equal, and in the same direction all the way around. Once
the iron core is placed into it, the field is induced equally all the way around creating the concentrated north and south
pole at the faces. Of course, we all understand that,.. goes without saying, but I said it anyway for the next step.
Magnetic field of single loop coil..png
Magnetic field of single loop coil..png (69.83 KiB) Viewed 563 times
In (a), I'll place the two sides of a long end turn coil next to a square core, and in (b), I'll go the other direction. Both
are making the same north and south pole, but of course, only half of the coil is used.
In (c), both sides are used, making the pole flux twice as strong as before. Should be the same for a trapezoid, but since
two sides are smaller, they contribute a little less. (OK, nothing new here...)
End Turns..png
End Turns..png (49.65 KiB) Viewed 563 times
In (d), I'll extend the core, so that the coil turns are distant, and only the face of the core is having an effect, then rotate
the core 90 degrees at a time. Isn't the flux that the PM sees, and used for torque, the same no matter the direction the
core and coil are turned?
End turn orientation..png
End turn orientation..png (101.81 KiB) Viewed 563 times

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Re: APL's DIY axial-flux motor

Post by major » May 14 2020 11:16pm

:bigthumb: :bigthumb: Image

This is different than the C-core design. Here the two radial coil sides will pass thru the magnetic circuit carrying the charge (as current) perpendicular to the desired force (tangential), as well as being perpendicular to the flux (axial, from the PM), completing the orthogonal Lorentz relationship. With the C-core, only one coil side passes through the core and it is tangential.

If you look at diagram 'a' in the image I posted of the SRM you'll see the reluctance force vector resolving into a large radial force and a meager tangential force (which is responsible for the torque). That large radial force causes difficulty with mechanical design. I've not been active with SRMs for quite awhile, but early in their development, frame distortion was a big problem. The noise was deafening.

Anyway, my point is twofold with that C-core design. One is the 75% end-turn and two is the Lorentz orthogonality when used with PMs. As shown in that article as a SRM, I'd be surprised if they could deal with the distortion with an axial layout like that.

Sorry for being off topic. It's just that I ocassionaly see that type of C-core axial design proposed for motors or generators and, if asked, discourage it. So I'm just on the look-out for an actual motor or analysis.

Regards,

major

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