In terms of excitation, the primary circuit used is the

• A. DC circuit
• B. AC circuit
• C. Control circuit
• D. Ground circuit

Answer: (A)

The field that creates the generator’s magnetic flux must be driven by a steady direct current. That steady DC in the field winding produces a constant magnetic field, which in turn allows the generator to induce an output voltage in the stator as it spins. If excitation were supplied with AC, the magnetic field would continually vary, leading to unstable output and regulation issues. The ground circuit is just the return path, and the control circuit refers to the regulator that modulates the field current, not the primary source of excitation itself. In practice, the DC excitation often comes from the aircraft’s battery or regulator to start and then maintain proper generation.