Higher frequency means smaller and therefore lighter transformers, which is very important on aircraft. Nowadays a DC voltage supply would be better, but DC to DC voltage converters didn't exist when the 24V 400Hz standard was created.
For mains voltage we use 50-60 Hz because lower frequencies work better with very large AC generators in power plants and, and lower frequencies are more efficient to transmit long distances.
Others have described why 400 Hz is useful. But I'll mention that this frequency is very inconvenient for using the box on the ground. Fortunately CuriousMarc had some vintage HP boxes that we could use. We ended up hooking up an HP 3310A function generator to an HP 6824A DC power supply amplifier to produce the power for the indicator.
Ah good. I was going to ask that question (does anyone has a 400Hz AC power supply lying around? :) - well I guess the manufacturers have but not many more people)
Higher frequency allows transformers and induction motors to use less steel in their cores for the same power.
In aviation, that matters because weight matters.
The downside is iron losses become bigger (heat lost in transformers). In a plane that typically doesn't matter because you aren't worried about losing a couple of watts of electrical power.
In today's world, it is irrelevant because all voltage conversion is done solid state (which is easier from DC), and all motors (of new designs) are brushless and therefore prefer to run from DC.
I know on the ground, 400Hz was a better match for turbofan electric generators. Which were lighter and more efficient than normal ICE generators. And so used a lot when the equipment was mobile.
> The unit is powered by 26 volts, 400 Hz, a standard voltage for aviation.
Any idea as to the history as to why this is the case?
I assume higher voltage is useful for lower amps? But why 400 hz?
Seems odd to use such a high voltage if components such as this must have internal transformers?