If rotor-to-stator air gap readings for an electrical generating machine have changed significantly from the last reading, what should be checked?

Correct Answer: Option C — the generator bearings for wear

Significant rotor-to-stator air gap variations indicate physical shifting, mechanical distortion, or advanced wear of the main generator bearings allowing the heavy rotor to drop out of center. Prompt inspection prevents destructive armature-to-stator rubbing and catastrophic electrical failure per IEEE 45 standards.