ES Motor Project?

[toolman2]

Just as some design info, the Sevcon is limited to ~500hz commutation freq (if I remember correctly).

The Kelly Ultra-High-Speed option is limited to 1100hz (in my testing, and it was getting glitchy past 1000hz).


I think the "infinions" can do something around 2000hz (but there have been so many versions and chips used by this point, I have no idea what current ones do).....

4000 rpm / 60 x 8 pole pairs = 533Hz commutation frequency.

ive been fondling with some high speed and ultra high speed kellys and the (quite similar) ca 120 (2.3kg) motor lately, and the kellys are good for quite a bit of commutation speed,
the high speed option (kelly quote 70000 erpm max) can do this and more.
so this motor has 28 mags (and a large 120mm can od and 24 teeth), so its 14 pole pairs so the kelly should run it up to 5000rpm. ive had it around 6000 just in the last few days (with a burties timing module a key ingredient..) and it handles this rpm well, the ultra high speed kellys quote 100000erpm so should do 7143rpm or more, and i can test this out if needed.

with this and the desire for a single stage reduction in mind, i believe you may want a higher pole count. this ca 120 motor has more poles than any other rc motor of this type and this changes stuff; firstly the no load losses are much higher for a given rpm than people seem to expect, so most are turned off straight away, but with this high a pole count AND 120mm can you dont want or need above 7000rpm as theres so much going on before this anyway, this along with double length teeth (with another near doubling of the iron losses) allows for double the copper, and all in all you have a motor that is very suited to low rpm high sustained torque.

seems to me like its having all the (both positive and negative) effects of high rpm without it acctually being that high, so to keep down the noise and gearing issues im thinking this is what you are after. and btw im thinking you would get more much needed inductance from more poles too?

the (2.5 times the kg) collosus is the opposite of this motor in these ways as its only 20 mags, lower inductance (suprisingly similar resistance) and wants revs.
-quality is not the problem, the collosus is extra hard to drive due to low inductance and simply scared everyone by needing around $1000 worth of controller, not a big drama though, works nicely in splinteroz's roadbike.

arlo put quite an effort into increasing inductance on the collosus -without success from winding changes iirc.
is it fair to say though, that more poles (well teeth really) give higher inductance, as there are just more little inductors inside?

 

[Arlo1]

Ok so lebowski's controller should be safe to add as an option. But I really really feal we need a low magnet pair number. Rpm is key to HP! Even if its wound for low rpm at first and as better controllers become avalible. I will be in 100% but only if high rpm is an option.
THUD. Were you talking about the 2 axis laser i linked? There is multiple lasers you can choose for it and diy starting at 1200. As soon as my head doesnt hurt im going to research it more.

Cheers guys very exciting. But controllers are where the effort is needed!

 

[bigmoose]

Large diameter inrunner would solve that problem... Does it have to be an outrunner?

You guys are going to "eliminate" the ol' guy for saying this...

If you went inrunner and added a misting Dextron Oil cooling loop, the sky would be the limit on PoWeR! ... Thud's already got the gearpump ready!

 

[Arlo1]

Large diameter inrunner would solve that problem... Does it have to be an outrunner?

You guys are going to "eliminate" the ol' guy for saying this...

If you went inrunner and added a misting Dextron Oil cooling loop, the sky would be the limit on PoWeR! ... Thud's already got the gearpump ready!

I am not sure i agree. Luke has soemwhat proven it. The way I see it cooling just lets you run at the max for longer but it realy doesnt change the limits of the iron and magnets they realy only can push pull so hard!

 

[nieles]

I am not sure i agree. Luke has soemwhat proven it. The way I see it cooling just lets you run at the max for longer but it realy doesnt change the limits of the iron and magnets they realy only can push pull so hard!

but you have to agree, that with the stator on the outside, cooling can be a lot more effective!

as long as you stay away from the stator saturation point, the only way to get more power from a particular motor is to have better cooling or a higher efficiency

 

[Lebowski]

I got some good experiences with forced cooling in my axial flux bike motor. What stopped the axial flux design, Miles ?

About my motor, the inductors are in a 5 mm acryllic glass (plastic) plate. You'd expect this to heat up very quickly
but I dissipated 150 to 250 W in there for about 10 to 15 minutes straight (going uphill at full throttle) and afterwards
it still felt only mildly warm to the touch. The 'sucking air through the shafte hole - flinging air out over the coils'
works extremely well...

 

[Miles]

I was thinking about the 40mm stator stack too. The only width difference between the hubbie design and a standard skirt bearing design would be the width of the hole to run the phase wires through. My drawing isn't anywhere near scale but with a 40mm stack, it should be very easy to get a sub 100mm overall width..

With a 40mm stack, you wouldn't necessarily require the extra support bearing...?

 

[Miles]

Large diameter inrunner would solve that problem... Does it have to be an outrunner?

I guess not. The larger the diameter, the more expensive the laminations, though. The Joby inrunners are already available at the 150mm size. Personally, I'd prefer 125mm, max.

 

[Miles]

Here's what a 5" inrunner might look like:

 

[Miles]

What stopped the axial flux design, Miles ?

Nothing, yet... I'm still intending to make one.

I thought we needed something a bit simpler for a communal project.

 

[Lebowski]

What I don't like about the inrunner design is that the place where torque is generated (at the airgap) is
about halfway between the axle and the outer shell. Keeping the I and windings the same (equal losses),
with the airgap on the outside of the design (like with an outrunner), you get the same force as with the
inrunner but the longer arm means you get more torque and thus more usefull output power per unit losses.

 

[Miles]

What I don't like about the inrunner design is that the place where torque is generated (at the airgap) is
about halfway between the axle and the outer shell. Keeping the I and windings the same (equal losses),
with the airgap on the outside of the design (like with an outrunner), you get the same force as with the
inrunner but the longer arm means you get more torque and thus more usefull output power per unit losses.

The larger the overall diameter, the less the difference in air gap radius needs to be, though.

 

[Miles]

5" inrunner with greater airgap radius:

 

[Miles]

with this and the desire for a single stage reduction in mind, i believe you may want a higher pole count.

Higher pole counts (& the likely higher teeth counts) need less rotor back iron and less stator yoke material. So, more room for copper equals less copper loss. The flux frequency goes up though, so greater iron losses. I guess that (for a given stator material) there's an optimum balance for every speed in the same way that there's an optimum balance for a given torque between the amount of copper to iron?

So, I guess we're back to:

What is the range of nominal speeds we need to cover?

 

[toolman2]

greater airgap radius yes, but that 2nd motor will now produce less continuous torque and higher copper losses cos its got less copper, its actually now a higher rpm lower torque motor, and also lighter and has higher very short term peaks.
-that 2nd one is getting a bit more like a joby..

so yep, just saw your post, "What is the range of nominal speeds we need to cover?

and you right arlo revs are the way to make power, what if you had to decide between revs and inductance?

 

[Miles]

greater airgap radius yes, but that 2nd motor will now produce less continuous torque and higher copper losses cos its got less copper, its actually now a higher rpm lower torque motor, and also lighter and has higher very short term peaks.
-that 2nd one is getting a bit more like a joby..

Not necessarily. The turning moment is greater, therefore the electrical loading is less for the same torque.

 

[Thud]

Wow,
take a 6 hour nap & there is a lot of reading to do.

Arlo: No. it was the E-bay engraving laser Luke linked too. I looked at a couple other sites last night, I may need to sell a few dirt bikes to afford anything like what I saw.....Still looking like a home chemical macining set up will be the way to personal laminations.

Inrunner? not out of the question, The only idea Ive had for something like a "DIY" Joby would be a stator made from very light gage iron wire bonded into a stator shaped object. Just need a mold & a high temp infusable resin...& a billion short lengthe of .005 wire

Bigmoose is right...if we took a Astro & spun it to its absolute max (thats above 20krpm's iirc) & activly cooled it.....it would deliver some mind blowing performance.

I think for a hi-powerd bicycle/moped, toolman2's aproach is also valid. Just a touque monster cranking a happy 2krpms will work also. & its encouraging to hear of some progress with the Kellys. IS all your testing on the bench? or have you tried it under some load?

Arlo & I are the exceptions looking to spin this thing into the 8k range (wich may just be un-reasonable with this topology without active cooling)

But all of this is really an aside, the 1st issue was & is, procuring non grain oriented hi-silicon steel for making laminations. The rest is a walk in the park.
If I hit the lottery it all become a mute point 8)

I would be curious to get a quote for the stators as they are currently in just a 20mm stack. It would have to be from china as I know how much anything on this side of the pond will cost form in-country suppliers. a new stator design & a minimum run is still spooky. (you can buy an = number of Astro's for what I was quoted for stators after adding tooling costs)

 

[Lebowski]

greater airgap radius yes, but that 2nd motor will now produce less continuous torque and higher copper losses cos its got less copper, its actually now a higher rpm lower torque motor, and also lighter and has higher very short term peaks.
-that 2nd one is getting a bit more like a joby..

Not necessarily. The turning moment is greater, therefore the electrical loading is less for the same torque.

Indication of an optimum !

 

[toolman2]

greater airgap radius yes, but that 2nd motor will now produce less continuous torque and higher copper losses cos its got less copper, its actually now a higher rpm lower torque motor, and also lighter and has higher very short term peaks.
-that 2nd one is getting a bit more like a joby..

Not necessarily. The turning moment is greater, therefore the electrical loading is less for the same torque.

yes, they appose each other like that so you would think it may go either way, but a comparatively large amount of copper is lost for a small increase in airgap radius.

 

[Miles]

yes, they appose each other like that so you would think it may go either way, but a comparatively large amount of copper is lost for a small increase in airgap radius.

That's true.

The copper area increases towards the outside. Better iron:copper ratio.

You are also increasing the airgap area.... I guess you'd need to reduce copper volume even more to take advantage of it, though...

 

[Miles]

so yep, just saw your post, "What is the range of nominal speeds we need to cover?

I'd say that we need to make something that is optimised for speeds between 2000rpm and 4000rpm but is still usable at around 6000rpm.

With the 16 poles, flux frequency at 4000rpm is 533Hz - so iron losses will still be relatively low for 0.2mm laminations. At 6000rpm it would be 800Hz.

 

[Lebowski]

sometimes I wonder, with all this motor and controller knowledge here, we should start a company

 

[Miles]

I would be curious to get a quote for the stators as they are currently in just a 20mm stack. It would have to be from china as I know how much anything on this side of the pond will cost form in-country suppliers. a new stator design & a minimum run is still spooky. (you can buy an = number of Astro's for what I was quoted for stators after adding tooling costs)

Here's my DXF. I guess we ought to use up the centre with a 55mm stator section that we could sell on........

 

[TylerDurden]

I checked the laser cutter last night. Everything says "do not cut metal", but the etched metal samples looked like the penetration was more than .2mm deep. :?

 

[mdd0127]

sometimes I wonder, with all this motor and controller knowledge here, we should start a company

I wish it was as easy as it sounds! If you did though, I'd be very excited about the future.