How is the output voltage of an alternator controlled?

The output voltage of an alternator is primarily controlled by varying the field current that excites the alternator. The alternator generates electricity through electromagnetic induction, and the strength of the magnetic field, which is created by the field current, directly affects the voltage produced by the alternator.

When the field current is increased, it enhances the magnetic field, resulting in a higher output voltage from the alternator. Conversely, reducing the field current decreases the magnetic field strength and thus lowers the output voltage. This method of controlling voltage is essential for maintaining the appropriate levels needed for various electrical systems within an aircraft.

Other choices involve different concepts that do not provide direct control over the output voltage. Adjusting the alternator itself is not a feasible or practical method to maintain or regulate voltage on a flight or operational level. Changing the load on the alternator does affect performance, but it does not regulate the voltage produced; it can influence the voltage to drop if the load exceeds the alternator's capacity. Modifying the battery connection could alter the configuration of the electrical system, but it would not dynamically control the alternator's output voltage in the way that adjusting the field current does.