What is the main reason of placing field winding on the stationary rotor?

Construction of alternator

The main components of an alternator or synchronous generator are rotor and stator. The rotor is a rotating part and the stator is a stationary part. 

In alternators, the field winding is placed on the rotor whereas the armature winding is placed on the stator.

Reasons for placing field winding on the rotor, not on the stator:

• Armature winding deals with the high levels of voltages, hence it is easier to insulate a stationary winding as compared to rotating winding.
• The stationary 3-phase armature can be directly connected to the load without going through large, unreliable slip rings and brushes.
• Only two slip rings are required for DC supply to the field winding on the rotor. Since the exciting current is small, the slip rings and brush gear required are of light construction.
• Due to the simple and robust construction of the rotor, a higher speed of rotating DC field is possible. This increases the output obtainable for a machine of a given size.
• For large-rating alternators, the construction of the armature on the rotor becomes more complex.

Mistake Points Here the question format given is same format asked in the official paper of SSC JE 2023 And they considered stationary rotor as armature in official answer