The term 'excitation' in an alternator refers to current in which circuit?

• A. Voltage regulator circuit
• B. Battery bus
• C. DC circuit
• D. Alternate current circuit

Answer: (C)

Excitation is the DC current used to energize the generator’s field windings to create the magnetic field that makes generation possible. That steady direct current flows through the DC excitation circuit to the rotor (or through a brushless exciter system) and is what the voltage regulator modulates to control output voltage. The stronger the excitation, the stronger the magnetic field and the higher the generated voltage; reducing excitation lowers the voltage. The generated alternating current in the stator is produced by this rotating magnetic field, not by the excitation itself. So excitation is a DC circuit, not an AC path, and the regulator’s job is to manage that DC excitation to maintain the proper output.