A synchronous machine is called a doubly excited machine because
Right Answer is:
Both its rotor and stator are excited
SOLUTION
Why synchronous Motor is called Doubly Excited Machine
Synchronous machines:- A three-phase synchronous machine is a doubly excited machine because its field winding is energized from a dc source and its armature winding is connected to an ac source.
When this is done, torque can only be developed at one speed-the synchronous speed. At any other speed, the torque is zero. In fact, it is this characteristic (i.e doubly-fed) that enables the synchronous motor to develop non-zero torque at ~only one speed (i.e. synchronous speed) and hence the name synchronous motor.
when working as a motor, the synchronous machine takes active power from an ac source. During its working as a generator, a synchronous machine delivers, or export AC power.
When this is done, torque can only be developed at one speed-the synchronous speed. At any other speed, the torque is zero. In fact, it is this characteristic (i.e doubly-fed) that enables the synchronous motor to develop non-zero torque at ~only one speed (i.e. synchronous speed) and hence the name synchronous motor.