APL's DIY axial-flux motor

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Thecoco974   10 mW

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Re: APL's DIY axial-flux motor

Post by Thecoco974 » Feb 18 2020 3:23pm

It look like an hybrid between a reluctance motor and an axial permanent magnet. The toroïdal stators are similar to some coreless motor we've spoken off before (but this Time they have an SMC core to loop back the field) and are interacting with the magnets I guess. And everithing else juste work like a switch reluctance motor. That's how i see it working

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fechter   100 GW

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Re: APL's DIY axial-flux motor

Post by fechter » Feb 18 2020 3:23pm

It's a radial motor. The "armature windings" are radial and pretty typical looking like you would have in a hub motor. Where it gets unique is the rotor. The rotor pieces are just iron and get magnetized by the "torroidal field winding" and a little bit from the permanent magnet. This allows much less magnet material (which could be expensive someday) to be used. It also allows for electronic field weakening.

Transverse flux motors are similar in many ways.

In a car alternator, the rotor is very similar. It gets magnetized by the field winding, which is between the two pole pieces. In this motor, they avoid the need for slip rings and brushes by having the field windings outside and the magnetism passes across a moving gap.
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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 19 2020 2:17pm

Still having a little trouble, the rendering lacks detail, The sides are stationary, the field windings, (not shown in detail),
are powered form outside, and the armature with the coils spin? Or does the armature and coils stay stationary, and the
sides spin,.. the field windings being induced by the armature coils and laminations?
hybrid-field-motor.jpg
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fechter   100 GW

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Re: APL's DIY axial-flux motor

Post by fechter » Feb 19 2020 2:37pm

My interpretation of it (which could be wrong) is the field windings on the sides and the armature windings are both stationary (so you don't need brushes for the wires). The shaft, toothed rotor and small permanent magnet are all connected together and spin. There is a small gap between the stationary parts and the moving parts. It can get a significant amount of its torque from variable reluctance (just the iron rotor attracting the armature coils) in addition to the magnetism imparted by the permanent magnet and the field coils. IPM motors would behave similarly.

With this design, it would be very easy to control field weakening and you could probably get the rotor to spin at very high RPM if you wanted. It's really like a car alternator except the field coils are outside the rotor instead of inside.
Car Alternator insides.jpg
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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 19 2020 2:59pm

OK,.. toothed rotor. Theres an air gap there, I missed that. I thought that the armature windings and rotor were one piece.
Now I get it. I was about ready to give up. :)

So it's a radial, and the field windings control weakening or enhance the field. The armature coils don't pictorially make
much sense, but I'll assume that they have it all worked out, and it's just a basic drawing.

How would it be controlled,.. one controller powers both sets of coils, and the side field current is adjusted?

I still don't quite see what the SMC around the shaft is for, unless it pairs with the diameter SMC ring, and connects the two
torrid's sides to 'box' in the rotor. A completed magnetic circuit. :?:

One things for sure,.. thats a heavy motor. It's solid steel and copper. But I suppose ecologically, it all good. We have lots
of steel and copper, but very little rare earth.

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fechter   100 GW

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Re: APL's DIY axial-flux motor

Post by fechter » Feb 20 2020 10:57am

The SMC around the shaft is to conduct the flux from the field coil to the rotor.
Any power used by the field winding is essentially wasted, so not an optimal design. Still interesting.
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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 21 2020 1:53pm

OK, one down,.. but now your alternator picture is bothering me. How is it that it has trapezoid rotors, but straight
stators? (at least, appears to.)

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Re: APL's DIY axial-flux motor

Post by fechter » Feb 21 2020 3:08pm

APL wrote:
Feb 21 2020 1:53pm
OK, one down,.. but now your alternator picture is bothering me. How is it that it has trapezoid rotors, but straight
stators? (at least, appears to.)
You are correct. I think they make them like that mostly for cost reasons. It is not optimal from an efficiency standpoint. The tapered poles on the rotor will give a more sinusoidal EMF than a rectangular one. Maybe this reduces noise as well. Guys have converted alternators into motors and you can get a lot of power out of them, but the laminations are thick (lossy), the air gap is big and you have to power the field to make it work or replace the field winding with permanent magnets. Efficiency is not great.

Back to your motor design, there really isn't a requirement that the magnets be the same shape as the stator poles but it optimizes torque.
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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 21 2020 9:48pm

I see. The sinusoidal EMF is a good point, cars have lots of electronics, and of course, the radio. I think the old military
planes had 400 htz systems, to make their radios quieter.
Cost reasons is another good point,.. high production parts.

I've been looking for axial motor FEMM's, to try and see just exactly where the flux concentrates on the magnet, and core
faces. Just like the back iron has a flux-split in the middle of the magnet,.. I suspect that the core does too.
And that the middle of the core plays less of a part than the sides. :?:

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Re: APL's DIY axial-flux motor

Post by APL » Feb 21 2020 10:41pm

The magnets are staring to line up, and looking little more like I wanted them too. It's like doing a mosaic. Theres a few
pieces that need to be re-done, but for the most part, it's going along pretty good. Developing an M.O. is most of it.
I can't recommend doing it this way to anybody else,.. to toxic, but it's good info to know, and at least, that it can be done.
Magnets V2..jpg
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Looks like I might able to leave the spacer bonded to the back iron, as it doesn't really get in anythings way.
I probably should have made the spokes another 1mm thinner, 4mm looks just a little bit to wide.

In one of my magnet searches, I found some 'windmill' trapezoids, as they call them. They're on liquidation pricing,
50mm tall, and 6mm thick,.. they're big dogs. 13000 gauss each!
16 of them edge to edge makes an 8" diameter, stator size motor. Perfect bike motor size.
That would make a real monster motor! 8)
(maybe V3)
CMS Trapezoid..jpg
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https://www.magnet4sale.com/n42-wedge-n ... -5-degree/

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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 23 2020 9:20pm

I'm still searching for a good FEMM of the trapezoid core in action, but haven't found one yet. Heres a good image of the
back iron though, and shows the flux 'parting line' in the middle of the PM's.
Axial flux distribution in back iron..png
Axial flux distribution in back iron..png (291.05 KiB) Viewed 1438 times
Also found this E-core concept, that uses Haibach style magnet concentration, on ferrite's, in another attempt at reducing
rare earth content. We've talked about using E-cores before, as they're abundantly available.
Taken from; https://www.nrel.gov/docs/fy15osti/64748.pdf
E core axial..jpg
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fechter   100 GW

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Re: APL's DIY axial-flux motor

Post by fechter » Feb 23 2020 11:08pm

APL wrote:
Feb 21 2020 10:41pm

Looks like I might able to leave the spacer bonded to the back iron, as it doesn't really get in anythings way.
I probably should have made the spokes another 1mm thinner, 4mm looks just a little bit to wide.
That might be a good idea. As long as it doesn't rub on anything it won't hurt to keep it in there.

Those big 5mm trapezoid magnets look pretty ideal. Maybe overkill but sometimes that's fun.
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Dui, ni shuo de dui   1 kW

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Re: APL's DIY axial-flux motor

Post by Dui, ni shuo de dui » Feb 24 2020 4:07am

APL wrote:
Feb 21 2020 10:41pm
I can't recommend doing it this way to anybody else,.. to toxic,
Can't you just cut the magnets immerged in a bucket of water?
It's pretty easy to do with a Dremel flexible attachment, this way you won't heat the magnets and you wont get any dust.
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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 24 2020 2:16pm

Those magnets are very tempting, and I'm still struggling with the idea. My budget is getting taxed from the current motor
project at the moment,.. plus we need the results from this build to make sure that things are viable.
But the little gears in my head are spinning, to be sure! It's not 'that' much $$. Hmmm...

A beefy motor with those magnets would probably need a re-inforced carrier, bigger cores, thicker back iron, and
thicker wire, plus a big battery and controller. Would be fun though, for sure. Might push the limit of bike parts
as a mid drive.

To add to the temptation,.. I have the Muscle Cruiser bike thats slated for a build in the near future, that would be a
good candidate for a big motor. And I came into a windfall of used lithium packs last summer, so I have batteries.

I know,.. not everybody likes cruisers, but I'm into them. :) Off road bike would be cool too, but I like asphalt.
V4 Concept..jpg
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Dui, ni shuo de dui, cutting in water is a good idea, and should take care of the heat, and dust, as you said. That would be
a good advancement in this tech for sure. The magnets aren't actually cut with the Dremel, just scored, but scoring them in
water would work better, if I can figure out a logistical way to do it, with water, and have good visibility.
I'm thinking I'll need to make a small machine of some sort for the task.

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Dui, ni shuo de dui   1 kW

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Re: APL's DIY axial-flux motor

Post by Dui, ni shuo de dui » Feb 24 2020 8:47pm

APL wrote:
Feb 24 2020 2:16pm
I know,.. not everybody likes cruisers, but I'm into them. :)
I don't really like cruisers but your design looks very, very nice. Can't wait to see it finished! :bigthumb:
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openwheel   10 µW

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Re: APL's DIY axial-flux motor

Post by openwheel » Feb 25 2020 12:43pm

Hello,

Just read through this whole thread, totally excellent discussion, learned a lot and very impressed.

Apropos of coreless stators, I wonder if you have seen this research by Sigbjørn Lomheim of NTNU? From 2013, not sure where it stands now.
https://pdfs.semanticscholar.org/e016/e ... 39a364.pdf

Though he was hoping to develop a traction drive for an EV competition, ultimately the topology appears best suited to ultra-high torque concentration in industrial settings where very high amperage is available, as a substitute for a winch.

But pretty neat concept nonetheless. Lots of detailed measurement, simulation and explanations.
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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 25 2020 2:45pm

Welcome to the ES openwheel, and welcome to this thread! I haven't seen that research, but it looks very interesting, and
is an awesome link. Just the kind of thing we need here, as it's chock full of information. It's going to take a while to go
through! :thumb:

Thanks for the great info!

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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 27 2020 1:31pm

Finally made it through that last link, or most of it, and put it in my favorites. So nice to see a motor article that uses
normal language to explain things,.. most that I have seen seem to go out of their way to use extreme technical
terms, making simple concepts non-understandable,.. at least, for me.

It was interesting to see him using, or at least talking about, the use of partial laminations with the coils, to increase
efficiency. (Magnetic)
Lots of good information about magnet skewing, and shaping, to reduce cogging and harmonics. Wish I would have read it
first, before starting on this venture. :)

Unfortunately, in the conclusion, the high copper content contributed to high eddy's, and made more of a magnetic brake
than a motor. But I'm sure that with some tweaking and more research, this could be overcome.

As I'm finding out,.. motors need to evolve, from one trial to the next, and it's a lofty expectation to think that it can be
done in one build.

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openwheel   10 µW

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Re: APL's DIY axial-flux motor

Post by openwheel » Feb 27 2020 1:44pm

Hello,

I'm glad you enjoyed reading it! In the same lines of readily consumable theory, I found this textbook is available for free:
https://www.academia.edu/38304436/Ebook ... tor_Design

And, only since I haven't seen it referenced on the forum (except for one link), I'll mention sci hub.
https://en.wikipedia.org/wiki/Sci-Hub

Also potentially of interest, is a parametric design of an axial flux motor I made yesterday:
viewtopic.php?f=30&t=104867

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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 28 2020 2:21pm

A powerful collection of links! :thumb:

Your parametric design tool is a great idea, and saves many hours of effort. Coupled with the Bavaria link for winding
schemes, one can visualize a viable axial motor concept in minutes. http://bavaria-direct.co.za/scheme/calculator/
Excellent work!

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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 28 2020 2:30pm

After looking at this chart of the magnet manufacturing process, I can see that the magnets are machined at the end,
and the last thing that is done, is the magnetizing. This begs the question as to wether a magnet can be re-magnetised.

I don't know what the machine for magnetizing is like, probably way out of reach for us, but still,.. I wonder. :?:
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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 28 2020 2:37pm

Here's a picture of a big windmill generator, in the process of getting some magnets bonded,.. talk about pinched fingers! :shock:
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fechter   100 GW

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Re: APL's DIY axial-flux motor

Post by fechter » Feb 28 2020 5:31pm

Just get one of those windmill generators and put it on your bike :twisted:

The magnetizing machine is just a big electromagnet powered by discharging a huge capacitor bank. Not totally impossible to DIY.
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APL   10 kW

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Re: APL's DIY axial-flux motor

Post by APL » Feb 28 2020 9:26pm

Thats good to know. I looked up neodymium magnetizing on Youtube, and found some videos of the process. I suppose
a person could make a machine, but I wouldn't want to,.. those things are rude!

https://www.youtube.com/watch?v=h7_z93Xklmo

But,.. there must be places that offer the service. Depending on the cost, it may be conceivable to cut and re-magnetise.
At least, maybe for bigger projects.

Also, water jet cutting may be a safe way to shape magnet segments. it would be dust free, and no heat. I don't think
that it would cost that much either. There are lots of local water-jet outfits. Just a thought.

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fechter   100 GW

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Re: APL's DIY axial-flux motor

Post by fechter » Feb 29 2020 1:10am

That was an impressively large power supply. 24 million watts.

I've never heard of water jet cutting magnets but would be worth investigating.
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