stator poles

[m3vuv]

I have a pair of 48v motors in bits,one is a 1kw chineese unit,the other is a 350 watt bion x,they are both direct drive hub motors,the chineese unit has 51 poles on the stator the bion x has 24,what difference does the number of poles make?.

 

[spinningmagnets]

When the same copper/steel mass is divided into more poles, it costs more to make, but the individual pole fields are smaller, and this means the "back iron" can be thinner, and thus lighter.

However, when a high pole-count motor begins spinning very fast (*72V-100V), it can run into difficulties in the controller with rapid switching, the electrical frequency. Maybe iron losses and inductance too?

Fewer poles costs less, but the required thicker back-iron weighs more. However it has less waste-heat when running extra-high RPM's.

Both benefit from less waste-heat from eddy currents if they use thinner laminations.

0.50mm thick laminations are common and cheap. 0.35mm is better, and the even when special-ordering at a higher cost, 0.20mm is near the theoretical best practical thin-ness.

 

[m3vuv]

thanks for the answer.

 

[m3vuv]

is one more efficient /powerfull over the other?.

 

[E-HP]

0.50mm thick laminations are common and cheap. 0.35mm is better, and the even when special-ordering at a higher cost, 0.20mm is near the theoretical best practical thin-ness.

Which companies provide special-ordering? At 0.20mm, I don't think I'd ever have any overheating concerns. I'm guessing with the improved efficiency, a 2 mile 20% climb (~2000ft) might be possible without overheating, maybe with just Statorade.

 

[spinningmagnets]

The Joby aero motors for the air-taxi use 0.20mm laminations (*I think?). I'm told that if you make them any thinner, the thin insulating varnish becomes a significant portion of the stator-tooth volume, and there's a reduction in performance at some point.

I don't know who you would order laminations from

 

[neptronix]

Higher pole count = better low RPM torque but iron losses increase the higher the RPM you run them, ideal for a hub motor with a large wheel.
Lower pole count = iron losses low, more suitable for high RPM ( IE inside a geared hub ), will have higher power density at high RPM.

~26 poles is typical for hub motors which will never spin beyond 1000RPM. 4 poles is more suitable for an RC motor spinning at ~10,000RPM

 

[E-HP]

The Joby aero motors for the air-taxi use 0.20mm laminations (*I think?). I'm told that if you make them any thinner, the thin insulating varnish becomes a significant portion of the stator-tooth volume, and there's a reduction in performance at some point.

Thanks. I just read about their stuff. Looks like the just signed a long term partnership agreement with Toyota. The whole electric passenger plane stuff is fascinating, but a little scary too.