The ROTATING ARMATURE-ALTERNATOR is essentially a loop rotating through a stationary
magnetic fealties cutting action of the loop through the magnetic field generates ac in the loop. This ac is
removed from the loop by means of slip rings and applied to an external load.
The ROTATING-FIELD ALTERNATOR has a stationary armature and a rotating field. High
voltages can be generated in the armature and applied to the load directly, without the need of slip rings
and brushes. The low dc voltage is applied to the rotor field by means of slip rings, but this does not
introduce any insulation problems.