The voltage coming out of the alternator depends on two variables: the amount of current flowing through the field coil (i.e. the strength of the magnetic field) and the speed at which the alternator’s field is rotating. Increase the speed, and you need fewer windings in the armature for the same power.
If you can match your frequency requirement to the speed the alternator will be rotating in service, then you don't need a step-down gear box either.
(Nice reply ASFKAP - shows your generosity of spirit.
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