Seriously another alternator question.

Before alternators, generator regulators often had over current cutout or regulation. It was a normally ON relay, with both coil and contacts in series with output. When current reached max design limit, contacts would open, hence current regulation.

Generators needed current regulation, because rotor carried current, and it was conducted thru commutator and brushes. In an alternator, output current is in stator, with lesser control current in rotor via slip rings. The stator has greater heat dissipation due to large radius, surface area an open frame design. Electrically the system impedance, and mechanical design, current limit, hence active current limit left out of regulator design. Things like rotor and stator impedance, with turns and wire diameter, diode rating, pulley diameters, and chassis wiring set upper current limit for most cases.