madin88 said:
It seems not, because the realtionship between the percentage of endturn copper mass and ETA is not like you still believe.
Hm. I suggest that you re-read what I wrote. I don,t believe there is
any relationship between end-turn mass and ETA (which I didn't even mention).
Whilst you continue to argue against that which I did not say,...
What did I actually say.
In the BionX D, with 84 teeth and an air gap circumference of 42", that's 1/2" per tooth. With an ~2.5:1 ratio of tooth face to gap, the tooth faces are 3/8". With room for 2 layers of 18AWG within the axial undercut, that leaves 0.214" as the axial width of the teeth.
Converting to metric to be consistent with your thread data, 5.445mm.
Layer 1: has 24mm of copper running axially, and 10.89mm of end turn: 10.89 / (24.0+10.89) =
31.21% end turn.
Layer 2: has 28.08mm running axially, and 14.96mm of end turn: 14.96 / (28.08+14.96) =
34.75% end turn
So, an average of 32.98% of the windings are end turns. Almost 1/3rd; I was being conservative when I said 30%!
Now let's consider the laminations:
With 4,436mm^3 of 0.018" US Steel Type 2, with a rating of 3.35W/lb (at 60Hz and 1.5T), what do you estimate your eddy current losses to be at (say) 1600Hz and 1T?
At certified rating of 60Hz/1.5T, it would be 35W; but eddy current losses are tricky. Beyond the headline "Finner is be'erer", there are a few other considerations to take into account; like frequency, harmonics, field strength...
BTW: When you were taking your BionX'D apart and taking all those photos your posted, did you notice:
How the phase wires -- red, white, black -- split into 4?
How those 4 sub-phase wires went to slots that were 90° apart, with 7-teeth between each of the 3 phases in each of the 4 quadrants?
Does 7 * 3 * 4 mean anything to you?
Do you remember your discussion with Justin_LE about whether this motors was 44000 eRPM or 22000 eRPM?
Oh, and did you notice how, for the 6 slots between of the 12 split phase wires, the copper from the last wind at the top of one tooth, goes diagonally in all 3 dimensions, to the bottom of the next adjacent tooth?
How would you feel if I told you that the eRPM of your motor (that I've never seen IRL, much less held or analysed), could have the same eRPM as a 11p12t motor. Ie (less than 2000)?
You know how you were disappointed with your experiments
First i noticed that it really cannot take much abuse in terms of phase current. It overheats still very quick when pumping more than 50-60A, so i set up the PV controller for 30A batt and 50A phase for the tour.
This was about 2500W of input power at an average battery voltage of 85V.
When going full throttle on the flat, the temperature did stop to climb after acceleration at an input power of about 2000W continuously at a speed of about 65kmh.
So it can do more than 2000W at high RPM which isn't bad for a 4kg DD motor pushing 125kg (45kg vetor bike + myself).
When climbing hills at 15kmh with the other ebikers, i was able to go up very long 12% grades (about 350 meter height in total without stop at 5km distance), BUT that was at only 500-800W of input power with the setting of 50A phase current. I needed to control the throttle very carefully, because even two seconds with too much throttle already led instantly to 10°C more stator temperature. The response of the thermistor on the windings is very quick. On hills or during harder acceleration it follows the twist of the throttle.
with the BionX'D, despite all the earlier promise from your rules-of-thumb, fag-packet calculations and simulator output?
Could it be that your intuition is wrong? That you were basing your optimism upon an incorrect model of how BLDCs work?
Just saying...
But I digress, back to the subject of...oh, what was it again? That's right, what I said about the efficiency of the BionX'D
iff you (et al.) were correct about the non-contributory nature of end-turns copper...
And how you (and others) misread that to read something about "ETA", which I didn't mention.
And how you accuse me of not reading what you write.
Bored now...
But, my simulation of your hot-rodded BionX'D just completed, with the upshot that at 20A phase current, the total losses from the tooth & hub laminations, back-iron and copper, at a conservative 1600hz, are: Tadah! A whopping great 5.5412W of waste heat
per tooth, for a total of 465W!
Could that be why it kept overheating?
Care to guess what they are at 50W/phase?