Does the rotor use brushes or a coomuntator? If not, does the rotor have integrated diodes?
When I used to repair generators, some types had two independent stator windings. One set of stator windings were used to control the "field" windings on the rotor to regulate the output, and the other stator windings were the output. One of the two sets of windings on the rotor produced an AC output which was then rectified to DC to produce the rotating magnetic field which then generated the actual AC output. The advantage to this type of design was NO BRUSHES !! Of course there was a slight hit to power efficiency.
