lowest cogging torque with best winding factor.

http://www.bavaria-direct.co.za/scheme/calculator/

will more cogging steps per turn equal less cogging torque the motor will have?

Yes, it will

thanks
I got a very high amount of steps with decent winding factor on there with 15N16P but am bummed to hear it would be imbalanced with only 3 teeth involved in torque.

the stator manufacturer discouraged 24 teeth as they've never seen so many teeth in roughly a 47mm diameter. with such a small motor I imagine the airgap width will come into play with the more teeth and poles. I just started modeling in motorsolver and hope it will be revealing.

I see what you mean. Not many that beat the 15/16 in that regard. I checked in Emetor

The 24/22 looks good apart from that it might be too thin..low cogging and really high winding factor and balanced.

Another way of handling it:
If it's a DIY one-off then couldn't you skip the slot openings and thread all the turns if you wanted to put the cogging torque as a lower priority? I've read it lowers eddy losses and reduces cogging. I can't remember any downsides except for the manufacturing difficulty.

Who will be doing the stators?

larsb said:

Yes, it will

Click to expand...

Are you sure? when the copper windings don't have any power flowing them, i don't understand how they'd contribute to losses we associate with the iron in the stator itself.

cogging is there even if there is no power.
The relation between LCM and cogging torque is explained here:
https://www.emetor.com/glossary/least-common-multiple-between-the-number-of-poles-and-the-number-of-slots/

I think it has to do with the magnetic flux path being disturbed at every slot opening but this is an assumption from my memory, it was too long ago that i was into motor construction to be sure.

This is a 47mm 24 slot outrunner stator, 1.5mm wide steel teeth isn't a lot :wink:

I think you misunderstood me. You're talking about the stator iron design, me and OP are talking about copper windings.

Yes, the iron segment cogs at no power but i don't see how the number of turns of copper would have any effect on how much cogging there is in any situation.

Cogging steps per turn of rotor, surely not turn of winding?

Nothing indicates that it’s per winding turn in the question..

with motorsolve it shows way less cogging torque with 24N28P than 12N14P with peaks of .015 newton meters vs .0045 with similar other geometry. But then the easier to make 15N14P combo blows them all out with .0008 Nm and also has minimal transits which I think makes up for its slightly reduced power factor and will have reduced iron losses compared to anything else anywhere near it's low cogging torque. It shows to be balanced at least in simulations..lord knows I wont figure it out staring at it. But I did read the 15N14P is INBALANCED. it doesn't show to be the case with some simulators, as you have above with emetor or Bavaria's calculator but does in motorsolve.
http://www.bavaria-direct.co.za/scheme/calculator/



For all stators there's less cogging torque with smaller slot opening. no surprise. ideal would be a .00001mm slot opening and that's how mellow electric skateboards does it, by having separate teeth wound and then assembled



maybe a simple way to get zero cogging torque could be to have two of the same motor wound in series on the same hub and rotor skewed 180 degrees

But 15slot's still imbalanced for the forces? Might be balanced electrically, it's not the same thing.

I really like the separated tooth winding, always wondered why it's not done like that. Simple,easy to wind, high fill factor, less risk for shorts.

I think some flux is lost in the divisions between the teeth but i don't know how much, miles looked at it back in his motor design days.

larsb said:

But 15slot's still imbalanced for the forces? Might be balanced electrically, it's not the same thing.

I really like the separated tooth winding, always wondered why it's not done like that. Simple,easy to wind, high fill factor, less risk for shorts.

I think some flux is lost in the divisions but i don't know how much, miles looked at it back in his motor design days.

Click to expand...

it looks hella risky with the teeth connected after winding and surely had taken development and not a nice out of the box option. ideal in ways for sure but the one person who i read from who had made a stator like that,Christian lucas of LRK winding name, said it was for trains and it broke.

i still don't even understand the forces that are at play and I've read all 3 phases are energized when running foc programs. if only two phases are producing useful torque then it would be imbalanced mechanical forces but if the bearings are well fixed and stout i dont see that as a problem. guessing!! hopefully someone with this rare tidbit of knowledge will throw a bone. kind of like the Harley of electric motors.. chugga chug. ..chugga chug.

This is my understanding: FOC running is aimed at keeping the rotor and stator fields at 90 degrees angle all the time, it’s the same goal for the trap controllers but they don’t do it as precise and they use only two phases at the same time.
Still the difference in main current (and forces) is not huge —> I guess that the force imbalance will still be an issue. It will lower efficiency to some degree and make noise.

im in the works of making a powder core to confirm it can be balanced and will work as well as hoped. I read it can be and looking at the drawing I can imagine winding it with transits across the stator instead of the whole phase being wound on 5 teeth beside each other. I read it can have a better winding factor than even the 12N14P

if shows well im going to get a custom die made for the 15 tooth. the prices for dies from china are all over the spectrum i guess largely depending on the die material. 3200 to 12000.

the die makers are discouraging me from a cheaper option ( I forget all the names) where Id just get the laminations and glue them myself but ive read of people doing that. I can imagine it would be time and work coating them all and stacking in some jig but doesn't seem THAT hard. if you have any experience either way I'd like to know. I'm a pretty small business so doing maybe 100 or 200 stators a year is a guess.