Jason,
I probably should clarify that I understood that you had these magnets and rotors and was responding to the original question of "about how many turns" for, in this case a 20-pole, 12', 24V alt. I didn't get into the prop design or matching aspect of it to know whether 12' is the right fit for this. Re-plugging the inputs, I get:
Assumptions:
magnet size -
length: 2.0 inputs in blue
width: 1.0
volts: 24.0
#poles: 20
rpm: 130
rps: 2.17
telsa 0.55
#coils / ph: 5
average emf: 4.0 (phi)f volts / turn
sine wave form factor:
1.1
rms volts / ph: 4.4
Surface Area of Magnets:
l x w = sq in =
2.0 1.0 2
x = sq cm =
6.4516 12.90
Total Flux / Pole: telsa x area (sq cm/10) mWb
0.55 0.71
line volts = rms volts/ph x 1.732, and
DC volts = rms volts/ph x 1.732 x 1.4, therefore:
rms volts/ph = DC Volts / 1.73 / 1.4 = RMS Volts / ph
24 1.732050808 1.414213562 9.80
line volts
16.97
Speed is: 130 rpm
2.17 rps
frequency = pn / 2 (where p = #poles, n = rps)
rps x #poles / = freq (Hz)
2.17 20 2 21.67
line Volts / rms/ph / (tot flux / pole / 1,000 / ) freq = #turns/ph
9.80 4.40 0.71 1,000 21.67 145
#turns/ph / coils/ph = turns/coil
145.0 5 29.0