Same debate again, motor windings!

Electric Motors and Controllers
Hummina Shadeeba   10 MW

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 05 2020 10:56am

When I say “where does it go?” Im referring to the energy loss. I know at higher speed it’s unnoticeable to a rider but it’s still there overlaid on the motor torque.

I haven’t read anywhere but ES that the energy of cogging is lost to micro vibrations and noise and that doesn’t seem possible at the low frequency of cogging. All I can see related to such a phenomenon would be magnetostriction:
https://en.m.wikipedia.org/wiki/Magnetostriction
but somehow silent.

if cogging produces heat that should be easy to show by slowly externally spinning a motor with awful cogging and temp sensors. I’ve never seen it shown cogging goes to heat.

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Toorbough ULL-Zeveigh   100 MW

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Re: Same debate again, motor windings!

Post by Toorbough ULL-Zeveigh » Feb 05 2020 2:41pm

roll a marble down an incline.
the floor is corrugated fiberglass or polycarbonate sheeting laid perpendicular to the incline.
where does the energy go?
why is it harder to pedal on a cobblestone road?

Hummina Shadeeba   10 MW

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 05 2020 6:05pm

What the hell?! I go looking expect to find an answer as to what is cogging torque through the analogy of the rolling ball on the undulating track and then this happens:
https://m.youtube.com/watch?v=_GJujClGYJQ

Pedal harder on a cobblestone road. So many things involved. But If we take the tires and tubes off and smooth the cobbles and make them more orderly and get the person and everything else off but one wheel I imagine work same as this ball.

I have no idea.

Is this track and ball analogous to cogging in ways?

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Toorbough ULL-Zeveigh   100 MW

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Re: Same debate again, motor windings!

Post by Toorbough ULL-Zeveigh » Feb 05 2020 7:21pm

that's beautiful; didn't occur to me to search utube.

yes, this is the analogy in which i view cogging.
if the analogy falls apart at some point i'm listening.

got another one for ya that i've been searching everywhere for years without success so if you find it pls post.
this wuz a demo by my hi-skool phyz prof that got me hooked on electronics.
take two bike rims mounted on the same axle in such a way that the rim walls are facing each other as close as possible without touching.
attach/glue a rubber stopper to a drill bit, mount the bit in a hand drill & spin up one of the rims to speed like a friction drive (or could use a prop-spinner).

what happens to the other rim?
1] turns in unison
2] turns the opposite
3] nothing, duh.
4] explodes

Hummina Shadeeba   10 MW

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 05 2020 7:28pm

What’s ur quote w the heavy metal sounding lyrics? I hear white snake r something but search nothing.
https://m.youtube.com/watch?v=vPQgfaB3S1c


And the wheels on same fixed axle or both wheels on bearings?
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Toorbough ULL-Zeveigh   100 MW

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Re: Same debate again, motor windings!

Post by Toorbough ULL-Zeveigh » Feb 05 2020 7:37pm

Last edited by Toorbough ULL-Zeveigh on Feb 11 2020 5:13pm, edited 2 times in total.

Hummina Shadeeba   10 MW

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 05 2020 7:43pm

Weird I searched even editing down to no frock and didn’t get that. Did end up searching Ryan Adams and heard his music in my head. Thought maybe ur own lyrics to his songs. Or white snake, which I don’t know at all, but at 14 Bryan Adams I probably listened to straight for weeks. That’s why I got hooked on searching and it’s stuck in my head. rare for me. ..and came upon that vid above I’ve never seen. But these days liking https://m.youtube.com/watch?v=knfrxj0T5NY
But fixed axle or bearings on both wheels

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Re: Same debate again, motor windings!

Post by John in CR » Feb 05 2020 7:59pm

Hummina Shadeeba wrote:
Feb 05 2020 10:56am
When I say “where does it go?” Im referring to the energy loss. I know at higher speed it’s unnoticeable to a rider but it’s still there overlaid on the motor torque.

I haven’t read anywhere but ES that the energy of cogging is lost to micro vibrations and noise and that doesn’t seem possible at the low frequency of cogging. All I can see related to such a phenomenon would be magnetostriction:
https://en.m.wikipedia.org/wiki/Magnetostriction
but somehow silent.

if cogging produces heat that should be easy to show by slowly externally spinning a motor with awful cogging and temp sensors. I’ve never seen it shown cogging goes to heat.
Just because our motors can't be heard while riding (using a good controller) doesn't mean they're silent. Haven't you spun up a motor with no wheel or load while stationary. They're not silent.

Regarding your test with temp sensors, you can't separate out the eddy currents and hysteresis that also occur.

Everything turns to heat in the long run, whether it's the sound in your ear buds or the energy content of the food you eat.

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 05 2020 10:10pm

It’s maybe hard to isolate from the bearing noise but if spinning a motor, unpowered, I doubt there’s any sound. Powered complicates it but looking at cogging forget power.

Eddies and hysteresis are high speed losses that are possibly not even measurable at the slow speeds speeds cogging is very noticeable. Iron losses wouldn’t be separable with the experiment and could add to the heat yea but considering the small losses they produce at 1000rmp at 60 rpm I don’t think they’re gunna make a dent. A “motor” could be designed to minimize those losses while also designed to heighten cogging for a test. Or a couple different to compare.

Every turns to heat but does just the pull of a magnet necessarily produce heat?
Nice resource: https://van.physics.illinois.edu/qa/lis ... tic-energy

If viewed like a gravitational the separation of a magnet from iron is like potential energy while. Falling in gravity isn’t a loss. Maybe.


Pretty neat:
“Magnets are a crucial part of collecting energy from heat: When one side of a magnet is heated, the other side—the cold side—gets more magnetic”

https://www.google.com/amp/s/phys.org/n ... energy.amp

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Re: Same debate again, motor windings!

Post by John in CR » Feb 05 2020 10:34pm

Cogging losses aren't much power. Yes, they do make a slight noise when you spin them up by hand, and sometimes when up in the air like that you can also hear the vibrations faintly resonate through the bike frame. If you do it with an old Xlyte X5 with the angled stator stack to eliminate cogging, it doesn't have noise or vibration...It's just heavy and not very efficient.

Spin one unpowered yourself, and you'll realize there have to be losses involved, and the manner in which it slows before stopping you'll realize it has to be cogging losses and end this off topic discussion.

Hummina Shadeeba   10 MW

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 06 2020 12:52am

Greatly reduced cogging torque with hair greater iron losses.

(Done with shifted not skewed magnets so not reduced torque)

http://kpubs.org/article/articleMain.kp ... _v11n4_878

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Re: Same debate again, motor windings!

Post by John in CR » Feb 06 2020 8:01am

Hummina Shadeeba wrote:
Feb 06 2020 12:52am
Greatly reduced cogging torque with hair greater iron losses.
(Done with shifted not skewed magnets so not reduced torque)
http://kpubs.org/article/articleMain.kp ... _v11n4_878
I'd suggest a bit less time reading and use that time to spend with actual motors. All you had to do was spend 5 minutes with a motor and what you would have learned would have prevented wasting so much time and thought about cogging, which is insignificant in the big picture anyway.

Hummina Shadeeba   10 MW

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 06 2020 12:42pm

theres a lot of interest in cogging besides from just myself and a lot of research out there into how to reduce it but none I can find explaining what the forces are specifically. if the energy is lost to heat how is that transformation done? 5 minutes with a motor..what would that show? if it irks you im in this thread I can start another. ill do that.

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Toorbough ULL-Zeveigh   100 MW

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Re: Same debate again, motor windings!

Post by Toorbough ULL-Zeveigh » Feb 06 2020 5:18pm

https://en.wikipedia.org/wiki/Gyrator%E ... itor_model
http://theijes.com/papers/ICIEEE/K085093.pdf
Hysteresis loss is associated with the phenomena of hysteresis and is an expression of the fact when ferromagnetic material is involved, not all the energy of the magnetic field is returned to the circuit when mmf is removed
it requires additional force to flip a magnetic domain even when static.
The force required to remove the residual magnetism from the material is called the coercive force or
coercivity of the material.

Hummina Shadeeba   10 MW

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 06 2020 9:10pm

you also think its hysteresis even after your great top link.
an easy test for seeing if cogging is due to hysteresis being putting all magnets in motor with the same polarity facing in. no?

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Toorbough ULL-Zeveigh   100 MW

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Re: Same debate again, motor windings!

Post by Toorbough ULL-Zeveigh » Feb 07 2020 6:39pm

somehow i just knew you'd come back with that.
the whole time as i was writing my previous post that i'd come to regret including 'flip'.

ok so you changed the parameters, no matter.
single polarity simply means you're in only half the hysteresis curve(you have seen the curve?) but it still applies just the same.
think of it as magnetic 'inertia' (which i'm sure you or someone will take issue with that too).
every shift in magnetic domains takes more force to get them moving than their 'momentum' returns as they come to rest.
anyway just wanted to dispel your notion that hysteresis only applies at high speed.

everything is an analogy therefore imprecise.
wikipedia wrote:The gyrator-capacitor model is, in turn, part of a wider group of compatible analogies used to model systems across multiple energy domains.
https://en.wikipedia.org/wiki/Mechanica ... gy_domains

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 07 2020 7:31pm

I assumed using one polarity the iron wouldn’t be thrown so far or something but now:

I don’t think there’d be any hysteresis in the all N up motor as the teeth would be exposed to the same continuous field as the rotor rotated all the same continuous polarity past the teeth.

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 09 2020 2:04pm

If all N up.. no hysteresis or eddies produced in teeth as same continuous field presented to them no? Not a switching field. Since cogging would still be there this should show cogging isn’t a product of iron losses?

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Re: Same debate again, motor windings!

Post by John in CR » Feb 09 2020 5:12pm

There may be no cogging, but probably no going either.

Hummina Shadeeba   10 MW

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 09 2020 11:21pm

There will be no going but that’s ok just to see. There will be cogging. And I think no iron losses no? Since no switching field.

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Toorbough ULL-Zeveigh   100 MW

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Re: Same debate again, motor windings!

Post by Toorbough ULL-Zeveigh » Feb 11 2020 5:07pm

Hummina Shadeeba wrote:
Feb 05 2020 7:28pm
And the wheels on same fixed axle or both wheels on bearings?
sorry man, i initially overlooked this.
yes, both wheels on the same axle would be the simplest to construct.
but that's not a requirement as long as the two rims run (very closely) parallel to each other.
so they can be physically separated but otherwise are co-axially aligned.

Hummina Shadeeba wrote:
Feb 07 2020 7:31pm
I assumed using one polarity the iron wouldn’t be thrown so far or something but now:

I don’t think there’d be any hysteresis in the all N up motor as the teeth would be exposed to the same continuous field as the rotor rotated all the same continuous polarity past the teeth.
not switching from one extreme to the other, sure the loss would be less but you wouldn't have a continuous field if the rotor is moving.
the field intensity is varying in both magnitude & direction as the magnet passes by the iron core (say left to right) even if the polarity remains the same.

magnetic domains are commonly depicted as tiny compass needles.
if a compass could be placed on the end of a stator tooth the needle will move following the N as it swings across.
but unlike a compass needle with a friction-free bearing that responds instantly, magnetic domains are stuck in molasses.
actually the word molasses (or inertia) are not a particularly good analogue since both imply a linear relationship when it is more of a step response almost like a detent (stiction maybe??).

if you've ever magnetized a screwdriver that's hysteresis.
wikipedia wrote:When an external magnetic field is applied to a ferromagnetic material such as iron, the atomic domains align themselves with it. Even when the field is removed, part of the alignment will be retained: the material has become magnetized. Once magnetized, the magnet will stay magnetized indefinitely.
now the very next sentence following the above quote talks about requiring the opposite polarity to demagnetize.
since this case is specified all N, demag won't happen but the domains are still in motion regardless.
however before they can get moving it takes a certain amount of field strength to first get unstuck from the position they're locked into which robs some energy.

now any magnetic field that passes thru a conductor produces a current (how a genny works) & this is what happens when a domain moves thru an iron core.
since iron is not the best electrical conductor, it's relatively high resistance converts that current into heat.
is this particularly hi speed?


WRT to the ball-track, cogging would be the energy-well represented by the hill/valley in the track.
hysteresis & eddy-current are the source of loss equivalent to friction, both air & rolling (even though a motor has both of those too).
if there were zero loss, then the ball or rotor would continue moving (almost) indefinitely just like things do in the vacuum of outer-space.
in either case the source of loss may seem small but it can have a seemingly large dramatic effect that is due to the relatively large (by comparison) energy-well.
as the system drops out of balance from small, gradual, continual accumulated loss it falls to ground giving up it's potential energy store.




as i get a little older,
i get a little bolder.
then roll it down a little hill.

good times.

Hummina Shadeeba   10 MW

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Re: Same debate again, motor windings!

Post by Hummina Shadeeba » Feb 11 2020 8:58pm

. then again id like to see all the graphs of lots of options.

if cogging were iron losses how does a skewed stator have more iron losses? what would the losses be if driven externally on a dyno (how would that power compare to the motor being driven itself?) i assume it will take more current to spin the regular stator than the skewed. why would there be more iron losses in non skewed? theres more iron losses it seems in the skewed according to the paper i posted.



need more skewed vs regular stator comparisons.

test being driven externally with no load at all rpm.

another model to test would be stator of aluminum. don't think they have that option on the program. gotta figure how to get dxl files to work better on there.

maybe the all North up motor could be modeled. I can run motor analysis program if the dxl file (?) will work. like to see how the magnetic poles pass an object as you say and in a simulaton it would say so much.

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