Dual field alternator in single field vehicle

Field polarity does not matter on the isolated field alternators.

The field energizes the electromagnetic rotor. The rotor has interlocking end plates that form magnetic poles. The curved lobes bent on the plates alternate N-S-N-S.... on the rotor circumference. Polatity does not matter, AC is always generated in the three stator windings, and full wave rectified by 6 diodes.