Tim,
The above posting is correct in that the one wire alternators have regulators built into them. Most common was the Delco 10SI used in the 70s and 80s as they were and still are very reliable. All of the 10 SI alternator were basically the same, different amperage ranges but basically built the same. They all took the same internal voltage regulator. To make one a self exciting alternator with NO wires going to the regulator you change the regulator. It excites off of the rpms. With this being said there are different self exciting regulators available and it all depends on which one the builder is using. When the self exciting regulators first came out they werent worth a dime on low rpm applications such as tractors etc. Because of the cut in at around 800 rpm or so. Since then aftermarket has come out with different versions, low rpm cut in regulators etc. They will kick in at a couple hundred rpms. The only way, that I am aware of, to get one to kick in about as soon as the pulley starts turning is to use an aftermarket regulator that is a small box that mounts on the outside thru bolt of the alternator. Its a special regulator that will actually allow the alternator to charge just about by spinning it by hand. Its more costly but works great on low rpm applications. As far as I know this type of alternator has to be custom built but so do most self exciting ones. Just an FYI and my experience in building them years ago.
Ken
