Why Do Jets Use Generators Instead of Alternators?
Arthur T Knackerbracket writes:
https://www.slashgear.com/2184041/why-jets-use-generators-instead-of-alternators/
A modern jet is an engineering marvel that's very easy to take for granted. Consider the uniquely engineered Boeing 787 Dreamliner, for instance. Step aboard this jet, and one of the things that's often just accepted without a second thought is the sheer quantity of electronics on show. First there are the visible devices like lighting, entertainment systems, and galleys to consider. Dig just below the surface, and you have the fly-by-wire systems, sensors, and the cockpit controls & instruments, each of which needs to be reliably powered. All in all, a Boeing 787 is threaded with about 57 miles of electric cabling.
All these electronics require a lot of power, the vast majority of which is supplied by the engines. However, the eagle-eyed among you will notice a big problem here - jet engines produce mechanical energy, not electrical, and something is needed to convert an engine's output into usable electrical energy.
There are several ways of converting mechanical energy into electrical power, but step aboard any modern jet, and it's going to be a generator that lets you watch the in-flight movie. While alternators are still used in smaller piston-engined aircraft, and the car in your driveway, the electrical demands of a modern jet are a different beast altogether.
Going back to the Boeing 787 and its 57 miles of wiring, the wiring schematic of this plane includes six generators, which supply power to 17 electrical substations. Modern aviation alternators are efficient, reliable, and lightweight. This begs the question, if alternators are so good, why don't jets use them? The short answer is scale. Electrically speaking, modern jets are ravenous machines - avionics, engines, climate control systems, and flight controls are all needed to keep the plane in the air and the passengers and crew comfortable. This requires far more power than a compact alternator can supply.
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