Please help me understand this

[qwerkus]

Hello,

I've been playing around with ebikes.ca's motor sim, and stumbled upon this.



How is it possible that a 9c 212 with only 56 poles reaches nearly the same climbing efficiency of a 10% slope than the infamous bionx D with 88 poles ? Sure the 212 has twice the stator width than the bionx, but shouldn't the extra poles more than make up for it ?

 

[pwd]

I think what you are seeing is that the extra copper in the RH212 is almost perfectly making up for the extra poles/diameter in the BionX. Also, you should adjust the rpm/v (under advanced) instead of the throttle to give a better comparison; although in this case they are almost the same rpm/v.

 

[E-HP]

I think what you are seeing is that the extra copper in the RH212 is almost perfectly making up for the extra poles/diameter in the BionX. Also, you should adjust the rpm/v (under advanced) instead of the throttle to give a better comparison; although in this case they are almost the same rpm/v.

Looks like that also impacts how long they take to overheat.

 

[qwerkus]

Also, you should adjust the rpm/v (under advanced) instead of the throttle to give a better comparison;

Care to elaborate ? Throttle is physically adjustable; rpm /v is fixed for a given winding.

 

[pwd]

Also, you should adjust the rpm/v (under advanced) instead of the throttle to give a better comparison;

Care to elaborate ? Throttle is physically adjustable; rpm /v is fixed for a given winding.

My thought is that when comparing two motors with different magnet widths and/or different diameters; keeping them at the same rpm /v in the simulator will help highlight the effects of those differences without the rpm /v difference skewing the results.

For your example: you wanted to see the performance of a motor with a larger diameter, narrow motor vs smaller diameter, wider motor. In order to isolate just those difference; wouldn't you want the rpm /v to be the same?

 

[qwerkus]

My thought is that when comparing two motors with different magnet widths and/or different diameters; keeping them at the same rpm /v in the simulator will help highlight the effects of those differences without the rpm /v difference skewing the results.

For your example: you wanted to see the performance of a motor with a larger diameter, narrow motor vs smaller diameter, wider motor. In order to isolate just those difference; wouldn't you want the rpm /v to be the same?

Got it! thanks for the explanations.

Still very surprised by those sim results. I always thought the ideal dd hub would be a 20" rim with something like 90-100 narrow poles. Now I realize it's probably a compromise between copper mass, poles numbers and stator diameter.

 

[E-HP]

My thought is that when comparing two motors with different magnet widths and/or different diameters; keeping them at the same rpm /v in the simulator will help highlight the effects of those differences without the rpm /v difference skewing the results.

For your example: you wanted to see the performance of a motor with a larger diameter, narrow motor vs smaller diameter, wider motor. In order to isolate just those difference; wouldn't you want the rpm /v to be the same?

Got it! thanks for the explanations.

Still very surprised by those sim results. I always thought the ideal dd hub would be a 20" rim with something like 90-100 narrow poles. Now I realize it's probably a compromise between copper mass, poles numbers and stator diameter.

I think the conclusion from the way you modeled it is that the motors have a similar kV, and that you could model totally different motors, but if they have the same kV, they perform similarly. The other conclusion from manipulating the throttle is that when using the same motor, but with different kVs, you can replicate the performance of the slower motor simply by decreasing the throttle of the faster motor. This is the biggest thing I've found with the simulator, since it demonstrates that there are virtually no advantages of the slow wind over the fast, except a negligible torque advantage down low, which pales in comparison to the huge torque advantage of the faster wind from the midrange on up, when both are running at full throttle.