You are correct. But from what Im using, my alternator is a 3 phase AC.
On a side note, (stupid notion) I thought thats why they call it alternator, its because its alternating current?????
Based on this wiki, most modern alternator have a built in rectifier diodes to convert it to DC, and a built in regulator to regulate the output voltage.
Thats why its common practice for those people who converts their alternator to make it wind turbine (successful or not) removes the voltage regulator (and sometimes rectifiers because they are built in to regulators) and just add rectifier diodes to make it DC.
Like this one...