Pulled apart another one to try it out. This one is wired in wye rather than delta, and I wanted to see what kind of difference it made to the numbers...
A lot more work to get connections on this one; the regulator et al is internal on it, whereas the first one is just sitting under a cover on the back. Had to run wires to everything to get external connections.
Final setup, about the same as the other one.
Results?
Less current and less RPM at full 80v/10v - 3750 rpm rather than 4700, pulling 10a max vs 13. Got up to almost as fast with field weakening, 80v/4v - 4900 rpm vs 5200, dropping the current down to 7a. Similarly unstable below 5v on the field.
Now, these aren't identical alternators, so they're not going to play the same, but it wasn't so different as I thought. The speed difference could be (partially) due to the field winding pulling 30-50% more current than the previous one.
It makes sense that a wye wound would run slower than a delta...as an alternator, a wye puts out more voltage vs rpm than a delta...so it's going to take more voltage going in to spin it at the same speed.
Wye is supposed to have more low end torque...I'd have to agree with that...the first alternator rocked a bit on a gentle start up, this one would try to jump, however gently you gave it throttle from a dead stop. Good to be able to choose to either have high starting torque or high full speed torque, depending on how it's wired up.
Bit surprised not to see either rev up stupidly fast...I hate to guess what kind of voltage can come out of an alternator with no load on it and the regulator bypassed...sounds like my next project.
I'm rather enjoying this silly project.