Alternator

The word “alternator” is a portmanteau of “alternating generator,” which means the alternator generates electrical energy to charge the battery and power electrical components. The other main components of an electrical system are the battery, master solenoid, master switch, bus bar, wire, and switches.

These terms can get a little confusing if you know that much older airplanes used a generator rather than an alternator to perform essentially the same function. Alternators are lighter than generators; they run at greatly reduced speeds, which means less wear and tear on the unit; and they are more dependable. A small amount of current (typically 1 to 4 amps) is fed into an alternator through the field terminal. Electrical power up to the alternator rating is available at the output terminal.

The alternator creates electrical current via a spinning electromagnet called a rotor that spins inside a conductor called a stator. As the rotor spins, alternating current created in the conductor is converted to direct current through a series of diodes that allow current to flow in one direction, but not the other. The current charges the aircraft battery; the battery provides all electrical power to the aircraft and the alternator’s primary role is to recharge the battery.