More power also entails a new design for the 777X’s generators, the airborne power plants using the plane’s jet engines to produce electricity. Since GE Aviation will be the sole supplier of engines for the plane — it developed the GE9X, the world’s largest jet engine for the 777X— the company decided to bid on the electrical system as well. In the past, a competitor provided both the main and backup generators for the 777. This time around, GE Aviation will build the backup electrical power system, including the backup generator, or BuG in industry shorthand.
A certification requirement for the backup generator is that it work in a wholly different manner than the main generator, says Joseph Krisciunas, general manager and president of GE Aviation’s Electrical Power Systems unit. “It has to have a different pedigree,” he says.
That’s because if there’s a design flaw that causes the main generator to fail, you don’t want the backup failing for the same reason. GE’s BuG uses the spinning rotor of the huge jet engine — it’s as wide as the body on a Boeing 737 — to turn a coil inside an induced magnetic field in the generator and produce alternating current. Since the frequency of the current varies with the speed of the rotor, the system has circuitry that converts it to direct current, and then converts the DC to AC at a steady frequency of 400 hertz, almost seven times higher than what Americans have in their sockets at home. The main 777X generator, by contrast, uses a mechanical linkage to keep the generator spinning at a constant rate.
GE’s BuG puts out 50 kilowatts of power from each of the 777X’s two engines — enough to power all the plane’s avionics and essential systems, but not extras like the galleys and coffee machines and entertainment system. “If you’re using backup power, you’re going to have to go without a movie,” Krisciunas says. It also synchronizes with the main power system, so that when power is shut off, the BuG kicks in without a break in the connection.
The 777X contract is part of GE Aviation’s push to apply technology it has developed for the military to commercial systems. The 777X’s BuG, for instance, builds on designs originally developed for the F/A-18 Hornet supersonic fighter jets and other military planes. To develop this commercial expertise, the GE business has invested more than $52 million in the Electrical Power Integrated Systems Center (EPISCenter), which opened five years ago on the campus of the University of Dayton in Ohio.
The idea was to develop a center of excellence for mobile electrical power systems. EPISCenter houses modeling and simulation tools, test cells, banks of computer servers and other technologies needed to support large engineering programs. The engineers working here have developed a full-scale replica of the 777X’s wiring, including miles of multicolored cables suspended in special racks from the ceiling, to test the BuG during development. “To develop these large systems, you need systems expertise,” Krisciunas says. “It’s not about just providing a generator. It’s providing an electrical system that integrates seamlessly with the rest of the aircraft.”