Great test and thoroughly done. Thanks!
Each phase segment came out almost exactly the same, so that eliminates one potential problem. You could go looking for other things like shorts into the laminations, but that's not likely. You didn't mention if the original motor had all 12 wires identified and carried out, or if you did that yourself. Mis-identifying wires on a phase backwards would cause a weak phase, but I doubt your alternator has any problems.
So a 1-Y star connection would measure about 5.6 ohms, exactly the same as the one I converted 2 years ago and ran with the 8' prop. In 2-Y it will be 1.4 Ohms line-to-line. Cut-in for 24v in 1-Y is about 90 rpm, or in 2-Y would be 180 RPM. Again, a lot like mine was, maybe a bit slower.
If my experience applies, you can expect about 500 watts, in 24v + 2-Y connection, when it's turning about 500 RPM. With my 8' prop, the wind had to be over 20 mph to accomplish that. Common where I live, in the winter. For a motor conversion with maybe 33% electrical efficiency at that current, the required input power is around 1800 watts.
The prop you've made has about 2x the swept area as the one I used. It won't match the alternator, no matter what you do. I was skeptical about using a 12' prop on a converted 3HP motor when I saw your first postings about it and I guess this shows what happens when you try.
The math on the prop goes something like this:
Diameter = 12'
Swept area = 113 square feet
density of air = 0.002378 slugs/ft-cubed (at sea level)
Wind speed = 25 mph
velocity is cubed, so (25*1.47)^3 = 49633 cubic feet per cubic second
A conversion factor of 1.355 is needed to go from feet+seconds+pounds to Watts.
0.002378 / 2 * 49633 * 113 * 1.355 = 9036 W
In these conditions, the wind will have 9000 watts kinetic power passing the 12' prop. Assuming Cp=20% you capture 1800 Watts at the prop, which matches the peak power of the alternator.
In contrast, an 8' prop would have 4000 watts of kinetic energy from the wind. But here though, you need Cp=45% to get 1800 Watts into the prop to match the alternator.
If the small prop isn't good enough to make a Cp=45%, then it will require faster wind to provide the 1800 watts cranking power. That was my situation, and as a result, mine could run unfurled if I wanted it to, and I tweaked the furling up and down until I got it just right.
If the large prop is well made (looks like yours), then it is capable of delivering 1800 Watts in much lower wind speed. Any faster wind and it will have a humungous energy. Though it isn't efficient, you will have great low-wind performance. The larger prop is always wayyy off its design point - it will be turning much too fast. But what happens when the wind blows stronger? You'd better have a bullet proof furling system. It may be difficult to "tune" the furling so that it protects well enough in strong winds >20mph, yet still can reach the 500W you want.
I get winds nearly 50 mph several times every winter. The 8' windmill could be electrically shorted, but be far from stopped in that condition. Turning several hundred RPM, even though it was furled out of the wind, too. Electric shorting will not hold your 12 foot prop, I bet.
Well, this morphed from Ohm's law to furling. It's all one system and everything is interrelated. It will work together, but you'll have to be careful. You might want to monitor RPM.
