How does a voltage regulator primarily control generator output?

The correct choice relates to the operational principle of a voltage regulator in a generator system. A voltage regulator manages the generator's output by varying the field current supplied to the generator’s rotor. The generator's output voltage is directly influenced by the strength of the magnetic field produced by the rotor. By adjusting the field current, the regulator can increase or decrease the magnetic field strength, which in turn modifies the generator's output voltage to maintain it at a stable level.

This method allows for precision control over the voltage delivered to the electrical system, ensuring it remains within designated limits regardless of variations in load demand or engine speed. The regulator can respond quickly to fluctuations, making it crucial for the reliable operation of electrical systems in aircraft.

While options like using a feedback loop from the output might describe a feature of some advanced voltage regulation systems, the primary and direct method for controlling the generator's output remains through adjusting the field current. Other options do not accurately reflect the fundamental operation of voltage regulation in a generator context.