Comparing motor specifications
- Thread starter Miles
- Start date
yep, i agree with continuous torque as the key spec.
and thanks for the info roller, yes im making a ~500a power supply to test amps vs NM output.
also if your still after dyno results, actual measured specs i have lots for the ca120,
heres one for said rc motor, at 11.2kw for a 2.2kg rc motor, the physics may or may not support it, but it happened anyway.
-actually i measured just 15.4NM max continuous (150deg c windings with a 10w fan)on my lathe dyno for a std ca motor, but here on the rolling road dyno (and a good rewind) we had a shop vac for motor cooling (cheating), and we saw 27.7NM from a standstill to nearly 4000rpm. its kinda beyond what i would have thought to be the motors continuous ability, but then again when you ride the bike you can't really hold this power for .5 sec anyway. :?
View attachment ca120 dyno graph.pdf
and thanks for the info roller, yes im making a ~500a power supply to test amps vs NM output.
also if your still after dyno results, actual measured specs i have lots for the ca120,
heres one for said rc motor, at 11.2kw for a 2.2kg rc motor, the physics may or may not support it, but it happened anyway.
-actually i measured just 15.4NM max continuous (150deg c windings with a 10w fan)on my lathe dyno for a std ca motor, but here on the rolling road dyno (and a good rewind) we had a shop vac for motor cooling (cheating), and we saw 27.7NM from a standstill to nearly 4000rpm. its kinda beyond what i would have thought to be the motors continuous ability, but then again when you ride the bike you can't really hold this power for .5 sec anyway. :?
View attachment ca120 dyno graph.pdf
roller
1 W
toolman - thanks for the curve -- that's pretty impressive stuff. What's changing between the 10 runs that causes differentiation? (motor/windings/voltage/temperature/ . .? ) Would be nice to know corresponding amps/efficiency along the curve . . , but I get that this is a wheel dyno.
Where do you strap on the shopvac on your bike?
Do you know what your (neo) magnet material is (S? SH? UH?) . . . 150C coils may put your mags in the danger zone. 15Nm -- what do you consider "continuous" -- 24/7? 1 hour? 1 sec?
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Miles -- like the paper describes, this method is likely valuable and useful for selecting 1 motor from a catalog of 1 manufacturer that is (ostensibly) consistent with their spec measurements/techniques/qualifications. But specs mean different things to different people, so it get's harder to apply across platforms/manufacturers. I hope for ES folks + motor suppliers/resellers will put up their independent curves, to build up a database . . .
Where do you strap on the shopvac on your bike?
Do you know what your (neo) magnet material is (S? SH? UH?) . . . 150C coils may put your mags in the danger zone. 15Nm -- what do you consider "continuous" -- 24/7? 1 hour? 1 sec?
----
Miles -- like the paper describes, this method is likely valuable and useful for selecting 1 motor from a catalog of 1 manufacturer that is (ostensibly) consistent with their spec measurements/techniques/qualifications. But specs mean different things to different people, so it get's harder to apply across platforms/manufacturers. I hope for ES folks + motor suppliers/resellers will put up their independent curves, to build up a database . . .
roller
1 W
toolman --
a thought about saturation that may be easier. . . (unless building 500A supplies is something you do in your sleep):
stator field/saturation is proportional to (A*t/mm) = "phase (pk) amps x coil turns per mm of stack length" . In some of our early motors, this was the magic "40" (At/mm) where saturation began . . . .A function of the steel quality, more than anything. . . . but tells how many amps a given structure can take before onset of saturation.
One can take an empty stator ; wind ONE pole 1,000 (whatever) turns of the smallest wire, and it will take very few amps to saturate it. . . but the formula holds, so you know what the amps will be at lower turn counts (or longer stack, etc).
Still required is measuring the field . . . I found an Android app " Max Mag Detector " which actually works. I can measure the strength/polarity/direction of a weak ceramic magnet from 10" away. I don't know if I've damaged my phone/sensor from playing with this -- it's a possibility with a lab full of N35 which corrupt my credit cards regularly (I swear that's why they don't work).
a thought about saturation that may be easier. . . (unless building 500A supplies is something you do in your sleep):
stator field/saturation is proportional to (A*t/mm) = "phase (pk) amps x coil turns per mm of stack length" . In some of our early motors, this was the magic "40" (At/mm) where saturation began . . . .A function of the steel quality, more than anything. . . . but tells how many amps a given structure can take before onset of saturation.
One can take an empty stator ; wind ONE pole 1,000 (whatever) turns of the smallest wire, and it will take very few amps to saturate it. . . but the formula holds, so you know what the amps will be at lower turn counts (or longer stack, etc).
Still required is measuring the field . . . I found an Android app " Max Mag Detector " which actually works. I can measure the strength/polarity/direction of a weak ceramic magnet from 10" away. I don't know if I've damaged my phone/sensor from playing with this -- it's a possibility with a lab full of N35 which corrupt my credit cards regularly (I swear that's why they don't work).
roller said:
thanks for the info roller, we changed phase amps and battery amps on a keb 10kw kelly, it seemed that above 50% setting on either didnt make any more, but the changes from 30% to 50% are what you are seeing, i video d the ca for each run and the most i saw was 12.4kw but it must be a little more than that.
yes i may need a 24s cordless leaf blower, as its smaller than a shopvac!
i dont know about the magnet grade, but ive done these temps a lot and it hasnt gained kv, but i acctually think the mags were too strong in this motor and that they are now weaker from being cooked.
continuous was for hours at 150deg c, but nothing was changing, so although its an unhealthy temp for increased copper resistance etc, i dont see it dying from it.
and yes a 500a supply will not be easy, but do you think the formula would hold when theres so much difference in tooth thickness, ie some motors have double the amount of tooth width (leaving less room for copper) but thers a good pic of this stator somewhere here and it has thin teeth and more copper?
-and its 3 turns of 23g 16 strands.
roller
1 W
toolman2 said:
it holds (and is intended) for variations upon a given lamination/stator (tooth geometry). The magic "40" is for a Transmagnetic 4", 12/8 pole motor only, of standard lam mat'l + thickness. But with that knowledge, I know what saturation is for all of our 4" motors of any winding or stack length.
The formula is not meant to apply across differing platforms / lamination designs, but needs be determined only once for a given lam design.
My suggestion is to find the "magic number" for your exact (or equivalent) stator, by winding one pole with many turns and measuring the field (Max Mag Detector = free) with a small power supply.
I recommend one pole, compared to fully wound stack (if possible) so that there is only one field generating source. An outrunner will be more easily measured with a phone than inrunner, if all poles are wound.
roller
1 W
don't know how it would relate to motor constants . . . but a nice generic motor metric would be the ratio of (real) continuous power (out) to peak power (out):
Pcont/Ppk
The closer to 1, the more "useful" or "optimized" or "effective" the thermal system is. As your efficiency or cooling improves, this ratio (or Pcont) increases.
This is most relevant for continuous duty applications (as opposed to vehicular traction).
Pcont/Ppk
The closer to 1, the more "useful" or "optimized" or "effective" the thermal system is. As your efficiency or cooling improves, this ratio (or Pcont) increases.
This is most relevant for continuous duty applications (as opposed to vehicular traction).
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