*
Battery
*
Battery No. 2
*
Captain’s flight instrument
*
First officer’s flight instrument
*
Standby ac.
After the RAT deploys, its generator supplies all of the power for the standby loads through the two center TRUs.
Control
The ELMS controls all the dc power system relays. (The RAT GCU can also control the TRU C1 relay.) The battery switch and the standby power switch supply manual control inputs to the ELMS.
The ELMS decreases the effect of faults in the dc generation system by normally keeping dc buses isolated. But, if there is a power loss to a dc bus, the ELMS can supply power to that bus from another dc bus. It does this by connecting the two buses. The ELMS uses these relays to connect dc buses:
* DC bus tie
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Page 15 D633W101-BEJ Sep 05/2002
DC GENERATION -FUNCTIONAL DESCRIPTION
*
Main battery The test takes less than ten seconds. If the system passes the
*
Battery-captain’s isolation test, no message shows on the EICAS display. If the system
*
Captain’s-first officer’s bus tie
fails the test, the advisory message ELEC STANDBY SYS
* Ground power battery.
shows.
Fault Isolation -DC/Standby Self-Check
The dc subsystem card does a check of the dc system. This is called a dc/standby self-check. It does these tests:
*
Makes sure all dc/standby system relays operate correctly
*
Makes sure the ac standby bus has power (this does a check
of the static inverter).
A dc/standby self-check can start either manually or automatically. You manually start the self-check when you set these conditions:
*
The airplane is on the ground
*
Left and right ac transfer buses have power
*
The battery switch is in the ON position
*
The standby power switch is in the BAT position
(momentary).
The self-check starts automatically when these conditions occur:
*
There are more than 72 hours since the last dc system test
occurred
*
The airplane is on the ground
*
Left and right ac transfer buses have power.
EFFECTIVITY BEJ ALL 24-30-00
Page 16
D633W101-BEJ Sep 05/2002
777 AIRCRAFT MAINTENANCE MANUAL
DC GENERATION -FUNCTIONAL DESCRIPTION
EFFECTIVITY BEJ ALL 24-30-00
Page 17
D633W101-BEJ Jan 05/2002
BATTERIES -GENERAL DESCRIPTION
General
There are two equivalent sets of battery equipment for main battery power and APU battery power. Each set has these components:
*
Battery
*
Battery charger
*
Current sensor.
The main battery components supply dc power to important equipment when other power sources are not available.
The APU battery components supply power to start the APU.
The battery switch on the electrical panel supplies a control signal to ELMS. This lets you supply main battery power to the battery bus 2 when the airplane is on the ground and has no ac power.
Batteries
The main battery supplies power to these buses:
*
Hot battery bus
*
Battery bus
*
Captain flight instrument bus
*
Battery bus 2.
These relays select the buses to get power from the main battery:
EFFECTIVITY
BEJ ALL
*
Main battery relay
*
Battery-captain bus isolation relay
*
Ground power battery relay.
The APU battery supplies power directly to the APU battery bus. The APU battery bus supplies power to the APU electric starter through the APU crank contactor. The ELMS energizes the APU crank contactor when the APU controller starts the APU.
The APU battery bus is also an alternate power source for the APU controller and the RAT deploy relay.
Battery Chargers
The battery chargers do these functions:
*
Change the ac power to dc power for the related dc buses
*
Charge the batteries
*
Send fault signals to the ELMS.
The ground service bus supplies 115v ac power to the main battery charger and the APU battery charger. The main battery charger charges the main battery through the hot battery bus. The APU battery charger charges the APU battery through the APU battery bus.
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BATTERIES -GENERAL DESCRIPTION
Current Sensors
Current sensors measure the current through the related battery. The ELMS EEU uses the current sensor output to calculate these data:
*
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