Why is 400 Hz preferred in aviation electrical power?

• A. It allows lighter, smaller transformers and motors for the same power rating.
• B. It reduces power losses in cables.
• C. It improves frequency stability.
• D. It requires heavier cooling.

Answer: (A)

Higher frequency lets magnetic components be smaller and lighter, which is crucial in aviation where every pound matters. For a transformer, the voltage it can transfer is tied to the volt-second product, which depends on frequency, the number of turns, and the core flux. If you keep the same voltage and allowable flux density (related to the core material’s limit), increasing frequency means you can use fewer turns and a smaller core while still delivering the same power. Since the core and windings largely determine weight, this reduces the size and weight of the transformer. The same idea applies to motors: a higher frequency lets the magnetic circuit be smaller for the same power, so you get lighter, more compact motors. That weight savings is the primary reason 400 Hz was adopted in aircraft electrical systems.