The initial excitation field for generators can be provided by which of the following?

• A. PMG (AC) or Pilot Exciter (DC)
• B. STANDBY battery system
• C. Ground power unit only
• D. Solar panel assisted regulator

Answer: (A)

The field current needed to start a generator’s output must come from a source already on the aircraft. In most systems, that source is either a permanent magnet generator or a pilot exciter. A PMG provides an AC voltage proportional to speed, which is rectified to DC to feed the main generator’s field, letting the generator build up voltage as it spins. Alternatively, a pilot exciter delivers DC excitation to the rotating or static rectifier arrangement that supplies the main field, enabling initial excitation and subsequent voltage regulation. Other options don’t provide the proper excitation path: a standby battery supports emergency buses, a ground power unit supplies external power rather than initial self-excitation, and a solar panel–based regulator isn’t a standard source for generator field excitation.