777 AIRCRAFT MAINTENANCE MANUAL
STANDBY POWER -RAT GENERATOR
EFFECTIVITY BEJ ALL 24-33-00
Page 5
D633W101-BEJ Jan 05/2002
STANDBY POWER -FUNCTIONAL DESCRIPTION -AC CONTROL
General
The ac standby bus uses single phase, 115v ac power. The left transfer bus is the usual power source for the ac standby bus. The static inverter is an alternative power source for the ac standby bus. These components control power switching to the ac standby bus:
*
AC standby power relay
*
AC standby control relay
*
Static inverter
*
P310 EEU.
Power to energize the ac standby bus goes through the ac standby power relay. The ac standby control relay controls the ac standby power relay. The EEU controls the ac standby control relay.
Standby Power Control
The left transfer bus normally supplies power to the ac standby bus. The static inverter supplies the power when any of these conditions are true:
*
Left transfer bus voltage is below 80 volts
*
There is an autoland bus isolation request
*
There is a dc/standby self-check in progress.
Static Inverter
The static inverter gets 28v dc power from the battery bus. The static inverter has a converter that increases the dc voltage, and an inverter that changes the dc power into single phase, 115v ac power.
The static inverter turns off for either of these conditions:
*
Standby power switch is in the OFF position and the airplane is on the ground
*
AC standby power relay is energized.
DC/Standby Self-Check
The dc subsystem card does a test of the dc system with a dc/ standby self-check.
The 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).
EFFECTIVITY BEJ ALL 24-33-00
Page 6
D633W101-BEJ Jan 05/2004
STANDBY POWER -FUNCTIONAL DESCRIPTION -AC CONTROL
EFFECTIVITY BEJ ALL 24-33-00
Page 7
D633W101-BEJ Jan 05/2002
STANDBY POWER -FUNCTIONAL DESCRIPTION -RAT GENERATOR CONTROL
General
The RAT deploys manually or automatically. The RAT switch controls manual deployment of the RAT. The ELMS P310 panel and the hydraulic interface modules (HYDIM) (not shown) control the automatic deployment of the RAT. When one or two RAT actuator solenoids energize, the RAT deploys. Then, the RAT GCU controls and monitors the RAT generator power.
RAT Deployment
To deploy the RAT manually, you put the RAT manual switch in the DEPLOY position. This energizes the two RAT actuator solenoids.
The P310 can deploy the RAT automatically. When the airplane is in the air and the two transfer buses do not have power for more than 15 seconds, the P310 energizes the RAT deploy relay for five seconds. The energized RAT deploy relay supplies power to the M29002 RAT actuator solenoid.
See the ram air turbine system section for more information on the hydraulic interface module card control of the M29001 RAT actuator solenoid (SECTION 29-20).
Power
The RAT GCU gets power from a PMG in the RAT generator. The PMG also supplies power to the voltage regulator. The voltage regulator rectifies the power to make dc current for the exciter field.
The generator uses the exciter field current to make ac current. The ac current goes through two relays to the two center TRUs.
Control
The GCU monitors the voltage at the point of regulation (POR). The POR is between the generator and the TRU relays. The voltage regulator adjusts the dc current to the exciter field to keep the POR voltage at 115 volts.
The GCU sends these signals to the standby power management panel:
*
RAT generator power ready signal
*
RAT generator voltage
*
RAT generator frequency.
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