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Magnax: Axial flux motor for EUCs


Beowolve
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I have searched for Magnax / Axial Flux in the forum, and it seams this topic hasn't come up so far.

There is a new company (Magnax) specialized in axial flux motors. This is also a brushless motor design and can also be build as a wheel hub motor.

It is basically superb in all aspects and allows for higher efficiency and at the same time very thin / small designs. 

So my question Is this type of motor allready used in some EUCs (IPS comes into my mind), or is this something that could improve EUCs in newer generations?

I am not a motor expert but this seams to be a no brainer for every EUC company. As I understand it, there seams to be no disadvantage over radial flux motors.

https://www.magnax.com/

Whitepaper

 

Here is the basic design difference:

6a00d8341c4fbe53ef0133ef5fb399970b-800wi

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21 minutes ago, Beowolve said:

I have searched for Magnax / Axial Flux in the forum, and it seams this topic hasn't come up so far.

There is a new company (Magnax) specialized in axial flux motors. This is also a brushless motor design and can also be build as a wheel hub motor.

Good question and possibly promising design, do you have any information are figures for its efficiency that are independent (I.e. not taking the company’s word for it)?

There is one word though that is likely to be a dirty word where uptake of this motor is concerned “Patents”. In reality efficiency increase is no more than about 10% (BLDC motors are 80-85% efficient) and it’s only real gain is likely to be in the motor being lighter. 

The company’s blurb suggests some manufacturing challenges I.e.

  • Rectangular section copper wire, for the highest possible copper fill factor (90%).
  • Concentrated windings, for the lowest possible copper losses (no coil overhangs).
  • Grain-oriented electrical steel, lowering the core losses by as much as 85%.

This suggests it would be a case of buying the motors from the company not making them yourself.

In conclusion a possibility for high value, high performance vehicles like electric cars, pretty much likely to be a complete non-starter for a small EUC or PEV maker (IMHO)

Edited by Keith
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Unfortunately I have no other information,  just read about that in on a german news site a while ago and instantly was thinking about  EUCs and wanted to share that info here.

Patents might me an issue, and if the motor cost is higher, it will have no success as well for sure.

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16 minutes ago, Beowolve said:

Patents might me an issue, and if the motor cost is higher, it will have no success as well for sure.

Not an issue if you buy them from the company that invented them. And it all depends on the motor cost indeed. Then again, what do you get in return? If the only return is that it will last longer no euc manufacturer will want to pay more. If you get a lot more efficiency/performance that might be different.

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4 hours ago, ir_fuel said:

Not an issue if you buy them from the company that invented them. And it all depends on the motor cost indeed

...and thereby hangs the point I was making. You almost certainly would have to buy them from the patent holding company.

Using square insulated copper wire in order to increase packing density is hardly going to be cheap. It will be challenging for a manufacturer to ensure adequate insulation at the sharp edges and the slightest twist whilst winding will have it cutting through a lower layer and shorting so great care and precision will be needed. It also looks like might require twice as many rare earth magnets and very controlled steel production to have the correct grain properties and orientation. Ergo, manufacturing costs will rise significantly (IMHO) For what appears to be around a 10% gain - it doesn’t look cost effective. How much would you be willing to pay for a 10% range increase for example.

I doubt many, if any, of our current  EUC manufacturer’s make their own motors (with the possible exception of Uniwheel and, of course, the Pulse Glider as that must be using Warp technology ?) but they almost certainly have a company in China knocking them out very cheaply by the 1000 and winding them to suit the application. 

Thereby hangs another point, I haven’t read through the white paper but we would need to understand the Kv and torque range of this motor as well. If the Kv isn’t in the correct range for a direct drive EUC or PEV that would kill any effeciency gain and might make it unusable.

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  • 3 years later...

Those motors sure seem to be gaining in popularity. One of the biggest manufacturers of those motors (UK company YASA) was recently acquired by Mercedes Benz who will be using those motors to power upcoming electric AMG Mercedes vehicles. Two or three years ago I asked about outrunner(=hub motor) versions of those motors in the comments section under one of the company's videos. One representative of YASA even answered me and said that an outrunner topology would be possible but that they hadnt made such a motor yet.

I think it is only a matter of time though, because such motors would be ideally suited for outrunner configurations. The biggest problem with the inrunner configuration is reinforcing and stiffening the rotors with the magnets against the enormous and rapidly shifting magnetic forces generated by the stator with the coils. In an outrunner configuration the magnets would be embedded in the huge and (because it is fully closed) extremely rigid outer case of the motor, which ought to  get rid of all stability issues. It would also allow you to use only ONE stator with the  expensive copper coils in the middle and magnets on BOTH sides of the cover for maximum efficiency.

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It begs the question:

--> What are the drawbacks of the motors in our EUC's today?

[radial-flux permanent-magnet position-sensor BLDC outrunner direct-drive wheel motors]


My thoughts:

  1. We've achieved just enough torque to make customers happy.
    We should treat today's Gotways with HB C38 @ 200A phase current as a 'minimum benchmark' for stall torque for an 18" tire size.
  2. More speed is always welcome.
    Decreasing output power with increasing speed is just a fact of life (for any electric motor design).
    Expanding the speed range using voltage is already hitting practical limits of affordable IC's, and electrocution safety.
    Expanding the speed range using variable gearing is excessive complexity and goes against our minimalist ideal for EUCs.
    Expanding the speed range using (electronic) field weakening may be possible (and could be employed on many motor types, including today's BLDC's).
  3. Motor overheating is almost unheard of.
    Our controllers burn first :)
  4. Neodymium magnets are expensive, bad for the planet, and susceptible to field weakening when hot.
    If we could achieve our goals without them, that would be nice.
  5. Mass reduction is always welcome... but you would have to cut the mass of the motor in half, to make a substantial difference in how an EUC performs.

So my proposal is: "We want more torque and more speed for the same mass and complexity."
(A man can dream, right?)
 

Axial-flux BLDC promises higher field strengths in the same package space. Field strength is good for torque and bad for speed... sounds like it shares the same drawbacks as the rest of today's EUC motors.

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