If the armature voltage exceeds its maximum allowed value, the windings could be
damaged. The angle of IA that requires maximum possible EA specifies the rated
power factor of the generator. It is possible to operate the generator at a lower
(more lagging) PF than the rated value, but only by decreasing the apparent power
supplied by the generator.
Synchronous motors are usually rated in terms of real output power and the lowest
PF at full-load conditions.