787 special: Electric dream
PrintBy: 12:00 26 Sep 2006 Source:
Boeing’s more-electric initiative is one of the major design features of the 787, offering increased efficiency, better control and reduced systems weight
The more-electric system on the 787 really is more electric, generating around twice the amount of electricity of a particularly power-hungry aircraft such as the E-767 airborne warning and control system. “It’s probably the biggest change to the systems architecture of any aircraft. We’re talking about a variable-frequency higher voltage system capable of 1.45mW, or enough for around 400 homes,” says 787 systems director Mike Sinnett.
There’s a lot of talk in the industry about whether we’re overextending on this, but frankly the engine doesn’t care whether its power is extracted electrically or pneumatically. We hear from the ‘equivalent horsepower’ school that a pneumatic engine is just as effective as an electric engine. But that’s the whole point; our aircraft does not draw as much horsepower off the engine in cruise, so it doesn’t burn as much fuel. If you look at the extraction profile you see the amount of power you pull off [the engine] is just what you need, so the engine isn’t working any harder than it needs to. We’re only getting what we need, and we only use what we generate.”
The bulk of the power comes from two 250kVA generators mounted to each engine