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Comment by buildsjets | Hacker News Reader

Aircraft AC electrical systems are 115V 400Hz, allegedly to minimize component weight.

> Induction motors turn at a speed proportional to frequency, so a high frequency power supply allows more power to be obtained for the same motor volume and mass. Transformers and motors for 400 Hz are much smaller and lighter than at 50 or 60 Hz, which is an advantage in aircraft (and ships). Transformers can be made smaller because the magnetic core can be much smaller for the same power level. Thus, a United States military standard MIL-STD-704 exists for aircraft use of 400 Hz power.

> So why not use 400 Hz everywhere? Such high frequencies cannot be economically transmitted long distances, since the increased frequency greatly increases series impedance due to the inductance of transmission lines, making power transmission difficult. Consequently, 400 Hz power systems are usually confined to a building or vehicle.

* https://aviation.stackexchange.com/questions/36381/why-do-ai...

Do electric car motors make use of this property too? I know some cars, such as Porches use higher voltage to enable faster charging.

Yes, but not just electric cars. Theres a push to move the entire electrical system of all cars from 12V to 48V to reduce the amount of low gauge wiring in a vehicle

Which is why trucks already have 24v as otherwise they would need too much wire.

Boats are also making that move. 24V is pretty common now with newer boats, and with electric propulsion 48V is quite attractive.

The NMEA2000 standard is confined to 12V however, meaning that all boats still need a 12V system as well. Maybe just with DC-DC conversion, or maybe with also a backup battery.

Very much true. A higher switching frequency means that a smaller transformer is needed for a given power load.

In reference to consumer power supplies, only reason why GaN power bricks are any smaller than normal is because GaN can be run at a much higher frequency, needing smaller inductor/transformer and thus shrinking the overall volume.

Transformers and inductors are often the largest (and heaviest!) part of any circuit as they cannot be shrunk without significantly changing their behavior.

Ref: Page 655, The Art of Electronics 3rd edition and Page 253, The Art of Electronics the X chapters by Paul Horowitz and Winfield Hill.

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