Why is 400 Hz chosen for aircraft AC power?

• A. It reduces weight and space by enabling smaller transformers and motors.
• B. It improves fuel efficiency at cruise.
• C. It reduces maintenance costs due to simpler equipment.
• D. It allows lighter, smaller transformers and motors, reducing weight and space.

Answer: (D)

Higher frequency reduces the size and weight of magnetic components like transformers and motors. For a given voltage and allowable magnetic flux, the core size needed to carry the power decreases as frequency increases, so you can use a smaller, lighter transformer or motor. In aircraft, weight and space are at a premium, so 400 Hz lets the electrical gear be much lighter and more compact without sacrificing the amount of power it can handle. Fuel efficiency at cruise isn’t directly improved by the frequency, and maintenance costs aren’t automatically lower; the main benefit is the weight and space savings from smaller electrical machines.