Howdy RB......Typical 3 phase automotive (and many other) alternators
will have 3 leads for output - the 3 resulting combinations of pairs are
each of the 3 phases outputting power. Looking closer at the winding to
lead connections you may see that each winding has a single wire
connecting to the output lead and that somewhere in the bundle you may
also see a 3 lead connection with or without a 4th lead attached - this
will indicate a typical 3 phase WYE connection......should you see 2
winding wires connection to each of the 3 output leads but no other
connection, this would typically indicate a 3 phase DELTA connection.
Each has it's own characteristics requiring more or less windings to
achieve whatever design voltage/current capacity is required. A further
or additional giveaway will be in the rectifier bridge associated with
what you're asking about.....3 phase alternators will typically have at
least 6 diodes and a typical rectifier will use 5 connections 3 for the
AC phases, 1 DC output and the ground connection whereas a single phase
winding (typically a single winding only with 2 leads) may have as
little as 1 diode (halfwave) or as much as 4 diodes in a bridge (this
may just look like a block with 4 terminals on it).

Hope this is a little clearer than mud to ya

Gord