Not 3 phase, AC ~ current
3 phase requires another set of windings 120
degrees out of phase (if I remember right) to
the windings that produce the single phase
cycle current
As for the brushes, I think they help in the process
of getting the alternator going at a low RPM. Not all
AC motors are induction, which have no brushes, some
like your hand drill and many small motors that are used
for work have brushes, these motors do not need a starter
winding and capacitors to get them moving, and have lots
of power at slow RPM speeds. Have you ever tried to use a
single speed hand drill ? not as much fun as a variable speed,
I break too many drill bits with them

Wild