In an AC machine, what is synchronism in the context of synchronous generators?

In an AC machine, what is synchronism in the context of synchronous generators?

• A. The rotor speed is synchronized with the supply frequency; rotor speed constant at n_s = 120 f / P.
• B. The rotor speed is synchronized with the supply frequency during startup only.
• C. The rotor speed varies with load to maintain voltage.
• D. Synchronism means the stator current remains in phase with the rotor current.

Answer: (B)