How does AC Alternators Work?

The modernization of aircraft has seen a correlated increase in the amount of AC power systems providing the vessel its electrical capabilities. Many of these electrical systems operate solely on AC. On the other hand, lighter aircraft tend to function better when using DC systems. The model AC electrical system would be composed of an AC alternator, a system that regulates the aforementioned alternator, as well as fuses and wiring.

Inverters are capable of bridging the gap when only a small amount of AC power is required. It serves a multi-function purpose, as it can also be used as a reserve power source on specific aircraft that employ an AC alternator. An inverter can also convert DC power into AC power when necessary. Many inverters are capable of supplying both 26-volt AC, as well as 115-volt AC. However, if both voltages are occupied, the power must be distributed on separate 26- and 115-volt AC busses.

AC alternators were designed for use on aircraft that employ a significant amount of electrical power. This includes all commercial and transport aircraft. In case of an emergency, these larger aircraft sport an additional AC power source (either an AC inverter or a small AC alternator). Modern alternators are designed to be exceptionally reliable and facilitate very little maintenance. They utilize a brushless technology that can transfer energy magnetically.

The core components of these AC alternators include three generator stages; each one functioning in different ways to create a harmonious design. The first one is the exciter generator, which is a stationary field composed of a permanent magnet alongside two electromagnets. The second generator is the pilot exciter which is mounted on the stationary part of the assembly. The AC output is supplied to the generator control circuitry where it is regulated, rectified, and later sent to the exciter field windings. The current then provides the voltage required for the last of the three components - the main AC alternator. The rotor continues to turn as the main AC alternator field generates power into the main AC alternator armature, utilizing electromagnetic induction. This final output concludes the three-stage AC process and is what essentially powers the different electrical facets.

This type of technology requires some sort of cooling mechanism. Oil is a common fluid used in successful cooling techniques, which is supplied by the constant speed drive assembly. Ports allow oil-flow between the constant speed drive and the generator. Oil level is critical to the success of the AC alternator.


March 11, 2020
February 25, 2020

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