What is the typical nominal DC power level for modern aircraft, and how is it regulated to maintain stability?

What is the typical nominal DC power level for modern aircraft, and how is it regulated to maintain stability?

• A. 12 volts DC; regulated by buck converters.
• B. 28 volts DC; regulated by regulators in generators/battery and TRUs to maintain a stable bus voltage.
• C. 120 volts DC; regulated by power conditioners.
• D. 28 volts AC; regulated by inverters.

Answer: (B)

In modern aircraft, the primary DC power is 28 volts. This voltage is kept stable across changing loads by regulation at the sources and the conversion stages. Engine-driven generators (with their regulators) control how much they output to hold the bus voltage near 28 V, even as power demand rises or falls. Transformer-rectifier units convert AC power to DC and regulate to the same 28 V, providing a clean, steady DC source. The battery serves as a backup and is kept properly charged by a regulator system so it’s ready if other sources dip or fail. This coordinated regulation—generators regulating their output, TRUs ensuring a stable DC from AC, and the battery charging/regulation—maintains a consistent 28 V DC bus across the aircraft.

In modern aircraft, the primary DC power is 28 volts. This voltage is kept stable across changing loads by regulation at the sources and the conversion stages. Engine-driven generators (with their regulators) control how much they output to hold the bus voltage near 28 V, even as power demand rises or falls. Transformer-rectifier units convert AC power to DC and regulate to the same 28 V, providing a clean, steady DC source. The battery serves as a backup and is kept properly charged by a regulator system so it’s ready if other sources dip or fail. This coordinated regulation—generators regulating their output, TRUs ensuring a stable DC from AC, and the battery charging/regulation—maintains a consistent 28 V DC bus across the aircraft.