Why are rotating armature AC generators less common than rotating field generators?

Rotating armature AC generators are less common than rotating field generators primarily due to their limited current capacity. In a rotating armature design, the armature itself is on the rotating component of the generator. This configuration can make it more challenging to handle high current levels because of the physical constraints and design limitations related to the armature's winding and size. High current requirements typically benefit from a rotating field generator, where the field windings are on the rotor, allowing the armature windings to remain stationary and be designed to better manage larger currents.

In contrast, rotating field generators typically have improved efficiency and adaptability when it comes to generating higher voltages and currents. This advantage makes them more suitable for many applications, especially those that require significant power output.