Motor comparison spreadsheet
- Thread starter Miles
- Start date
crossbreak
1 MW
Do u know shaft dia and bearing size? I can do a DIN calc analysis on overload fracture. Won't be as accurate as calcing the while calc but it will give you a number. I also need sprocket effective dia too.
For the cyclone 1680w motor no load measurement did you try it without the motor seal ? Most motors do not have a seal whereas that one does. Also IPM design has LESS eddy current losses not more, and its the reason why Zero motorcycles went to them this year , here is a video of the benefits of IPM design :
http://www.motorcycle-usa.com/2015/12/article/zero-motorcycles-ryan-bifford-explains-new-z-force-motor/
crossbreak
1 MW
yep, thats also my opinion. but he is right about the .5mm lams being bad for eddy loss..still we calced a figure that seems much higher speed then cylcone proposes. speeding up this thing seems to be good in terms of efficiency/continuous power.
For the cyclone motor to make it even more efficient, would it be better if the motor was rewound to a higher KV, like say 150-175kv which would mean lower winding resistance and hence lower copper losses? Because at 72v in your chart crossbreak it seems eddy current losses are a lot lower then copper losses ? what is the ideal balance point you want to have between winding and copper losses at peak power ?
Thats a great message Luke, for all the motor designers out there to put some effort in and stop pissing around. :lol:
dunno, i still think rpm (say more than the wheel needs directly) will likely play its part in future high power density motor development..
-aand i think there will likely also be a place for race bikes that are on rough tracks or terrain to not want the motors weight on the wheel, but suspended low in the frame.
Ive given this some thought Miles and other than being greedy (maby for more torque via extra iron and copper via tooth length etc -and thats not realistic with in the same dia without making the rotor smaller) cos the other bike components prolly max out first, the motor really is spot on, and also very similar to your designs. :wink:
dunno, i still think rpm (say more than the wheel needs directly) will likely play its part in future high power density motor development..
-aand i think there will likely also be a place for race bikes that are on rough tracks or terrain to not want the motors weight on the wheel, but suspended low in the frame.
Miles said:
Ive given this some thought Miles and other than being greedy (maby for more torque via extra iron and copper via tooth length etc -and thats not realistic with in the same dia without making the rotor smaller) cos the other bike components prolly max out first, the motor really is spot on, and also very similar to your designs. :wink:
speedmd
10 MW
Hi Toolman2
Enjoyed very much your video of your ebike dropping the gassers.
Is the JM1 a much better choice than the JM1S if your gearing for higher speeds without giving up too much low end torque or acceleration in tighter-slower sections.
Enjoyed very much your video of your ebike dropping the gassers.
Is the JM1 a much better choice than the JM1S if your gearing for higher speeds without giving up too much low end torque or acceleration in tighter-slower sections.
The 46p Joby (JM2) is also interesting. Optimised for torque density, rather than power density (as we're frequency limited).toolman2 said:
I've settled on 34 poles in a 120mm O.D. motor, to experiment with. We'll see how that works out....
speedmd
10 MW
Interesting comparison in the JM1 and the JM2 given the difference in top end RPM. I would think the lack of high RPM capability of the JM2 possibly somewhat limiting in usable top end vs the 9000 rpm limits of the JM1. Screamer vs something more like a diesel! Not sure what works out best, lighter geared lower with more rpm range or something more steady- torque.
Compare the continuous torque density of the JM1 and the JM2S, which are close to the same mass....speedmd said:
The scaling effect is quite significant and needs to be born in mind, too.... One large motor should always beat two smaller motors of equivalent total active mass....
speedmd
10 MW
Understood. However, the area under the torque-power curve is what may be more important in the motors overall usable range vs speed constraints. A broader rpm range may win out when all is considered. No argument on the larger is better effect. Doing so and also not giving up the high end revs would be a no-brainer. Have to say it would be great to have something the diameter- torque of the JM2s with a 9000 rpm max. Wee.eee.eeee..! 
speedmd
10 MW
Can not stop thinking of the possible advantages that internal magnets may bring to increasing rpm range/ reducing iron losses in this class of motor, even if it loses a bit of max torque and adds a bit of weight.
Miles said:
I wonder why Joby went wich such thin and expensive laminations, instead of lowering the pole count.
Such lower pole motor would not be that lightweight anymore (more iron needed for the stator and for the magnet return), but fwik, half poles should mean half the eddy losses while torque stays the same. additionally they could increase the copper fill with such stator.
or did i miss something? are there any other disadvantages of lower pole count?
Advantages of higher pole count:
Less iron needed for the yokes (as you said). For a given O.D. this allows either, an increase in copper cross-sectional area or an increase in gap diameter and area.
More options for a higher winding factor.
Possibility of higher LCM (more cogging steps per revolution).
Possibly, there's a small advantage in torque from the pole count but it's not clear why.....
Less iron needed for the yokes (as you said). For a given O.D. this allows either, an increase in copper cross-sectional area or an increase in gap diameter and area.
More options for a higher winding factor.
Possibility of higher LCM (more cogging steps per revolution).
Possibly, there's a small advantage in torque from the pole count but it's not clear why.....
crossbreak
1 MW
it also looks like they use rectangular bar magnets instead of shaped magnets. The more used the more the polygon becomes almost a circle.
i'm not so sure if this really exists. I cannot find a valid conceptual model that proves why a motor with more pole count shall produce more torque/should be higher Km². If you just want thinner yokes, you can simply use high slot count like the leaf does. You most likely get a better winding factor: A 12n8p has 0.866 while the 48n8p has 0.966. An incrase in Km² of 24%. Both being the same pole count. the 48n will be more expensive to produce
Miles said:
this is for inrunners, right?
how would two outrunner motors compare in terms of copper fill?
both have same gap diameter and same stator width, but one has high pole count and one has low pole count.
what i really like on high pole hubmotors is that the iron needed for the magnet return can be very thin
madin88 said:
Perhaps it's better to talk about copper area? Copper fill usually refers to the percentage fill of a given area.
Keeping it simple.... You need less iron for a higher pole count so, the weight saved could be used to deepen the slots, increasing the active area?
crossbreak
1 MW
Since the back iron of both stator and rotor are thinner. But the sum of the tooth widths will be the same, as the ratio of slot width to tooth width shall be the same for equal torque abilities, 50%/50% for example.Miles said:
So what is saved on weight basically is back iron.
Edit: cross-section of the stator backiron should depend on slot count while rotor' backiron depends on pole count. Could we say so? somehow depends on the winding scheme..doesn't it?
Edit2: Just depends on pole count, increasing slot count alone does not help
crossbreak
1 MW
that brings me to the idea of an axial sandwich motor that lacks of stator back iron: One rotor, then the stator and then another rotor: Still two backiron parts, but they both are in the rotors. These virtually have no eddy currents and need less cross-section than stator back iron does
crossbreak said:that brings me to the idea of an axial sandwich motor that lacks of stator back iron: One rotor, then the stator and then another rotor: Still two backiron parts, but they both are in the rotors. These virtually have no eddy currents and need less cross-section than stator back iron does
Been there: https://endless-sphere.com/forums/viewtopic.php?f=30&t=36368
crossbreak
1 MW
yep, been there, thx for the link
backiron thickness should be about half of the tooth width?
backiron thickness should be about half of the tooth width?
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