Welcome, Paul!
Your electrical questions are probably best asked over in the electrical forum.
I do know that when adding an alternator to an old tractor that one of those wires is sometimes run to a generator light of some kind. Another option is to put a diode in the circuit. If you don't do that the thing will keep running even after you turn the switch off.
That's about the extent of my electrical knowledge! As mentioned, ask the guys in that other forum for a better explanation.
