The excitation current path for an airplane alternator is typically described as which circuit?

• A. Battery bus
• B. DC circuit
• C. Power distribution circuit
• D. Ground reference circuit

Answer: (B)

The field winding of the alternator must be energized with direct current to establish a steady magnetic field that allows generation. The excitation current is drawn from the aircraft’s DC electrical system through the regulator to the field terminals. The regulator then adjusts this DC current to control the generator’s output voltage. While the generator’s output is AC in the stator, the excitation path itself is DC because it powers the rotor’s field. If excitation were not DC, the magnetic field wouldn’t be stable, and the alternator wouldn’t regulate properly. The other circuits are related to distributing or grounding power, but the excitation path is specifically a DC circuit.