787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Electrical Chapter 6
System Description Section 20
Copyright © The Boeing Company. See title page for details.
D615Z003-TBC 6.20.1
6.20 Electrical-System Description
Electrical20 System DescriptionSystem Description
Introduction
The 787 airplane electrical system generates, distributes, and manages airplane
electrical power. System operation is automatic. In addition to traditional
electrically powered systems, the 787 electrical system powers engine start,
pressurization, wing ice protection, stabilizer trim, and wheel brake systems. The
system primarily uses 115 Vac and 28 Vdc power, with a limited number of
systems optimized with 235 Vac.
Electrical System Power Sources
The electrical power sources are:
• four variable frequency engine starter/generators
• two variable frequency APU starter/generators
• three external AC power receptacles
• one Ram Air Turbine (RAT)
• one main battery
• one APU battery
• three flight control Permanent Magnet Generators
The power sources remain isolated from each other throughout the generation and
distribution channels. During power transfers, a brief power interruption may
occur as buses are energized from a new power source.
Engine Starter/Generators
The engine starter/generators function as electrically powered starter motors for
engine start, and as engine driven generators once the engines are running.
Each engine has two 235 Vac variable frequency starter/generators. L1 and L2 are
mounted on the left engine. R1 and R2 are mounted on the right engine. They are
directly connected to the engine gearboxes, producing variable frequency power
proportional to engine rotor speed.
Electrical power for engine start can be provided by external power, APU
generated power, or the opposite engine’s generated power. The electrical system
automatically selects both starter/generators to engage in order to provide optimal
torque for engine start.
After start, the starter/generators function as generators to energize their
respective main AC buses, also designated L1, L2, R1, and R2. Generator status
is shown by generator switch indications, MFD electrical synoptic, and the EICAS
message system.
August 14, 2009
To Next Page
Loading...
