Cheers Bryan,
Looking nice buddy. Regarding that 300 rpm..seems we are still a tad over that? This "mini" is turning out to be a hair bigger than you first planed...2.5 meters (8.2 feet)
For the benefit of those following along and others looking for information in the future, hope it's OK to go into the easy maths we are using here to figure cut-in?
Using our test results above we can take a reading..lets use the 450 rpm (that one cross references very nicely with some of the others as well as with the projected Hz reading).
We see a reading of 3.2VAC at 450 rpm..that will let us get a very good idea of what a finished machine might do.
3.2 VAC X 4 coils in series =12.8 VAC
12.8 VAC X 1.73 (star connected 1 WYE stator) = 22.14 VAC
22.14 VAC X 1.4 (AC RMS to DC conversion) = 31 VDC
we can take that 31 VDC and divide by 450 rpm and find we get 0.0688 volts per rpm.
on this machine Bryan is looking to charge a 24 volt bank of batteries.
A lowish battery bank on a 24v nominal system might be about 25 volts.
For cut-in we need 25 volts plus 1.4 volts rectifier voltage drop = 26.4 volts to start charging.
26.4/0.0688 = 383 rpm cut-in with the above 45 turns at the airgap tested.
Hope that sounds reasonable.
cheers, dave