What is the role of the alternator field circuit?

• A. It supplies the main electrical power to loads.
• B. It bypasses the regulator.
• C. It controls the magnetic field strength within the alternator to regulate voltage and current output.
• D. It converts DC to AC.

Answer: (C)

The field circuit provides the excitation that creates the magnetic field in the rotor. The regulator controls how much current flows through the field winding, strengthening or weakening the magnetic field. A stronger field increases the voltage generated in the stator, while a weaker field lowers it, so the regulator adjusts the field current to keep the output voltage within the desired range as speed and load change. This is the mechanism by which the alternator’s output is regulated.