Electrical System Flashcards
Where does the AC power normally come from?
Two AC IDG
Plus Ext AC APU
Where does the DC power normally come from?
4x TRU
two batteries and Ext DC
What buses does the AC normally supply?
AC Bus 1
AC Bus 2
Ess AC Bus
(plus indirectly to galley bus 1 2, Emerg AC Bus, AC GND SER Bus)
What buses does DC normally supply?
DC Bus 1, DC Bus 2, DC Ess Bus, Emerg DC Bus, DC GN HDLG Bus, DC GND SER BUS
(plus indirect Dual DC Bus)
If a AC generator power is lost, what power is still available?
If running on one, all buses will be powered, except galley bus de-energizes.
What alert is presented i a AC Generator power is lost? Where will the alert be shown?
A level 2 Alert (2 chimes, caution light, GEN1/2 on MDFU and local fault light)
How long would you expect the batteries to last if you lose all generators?
30mins
On the ground, how can you expect the ground handling and ground service buses to be powered?
Via APU or via AC ext power. BAttery
When external AC is plugged in, but not switched on, what is powered and what indications would you get?
You will get a AVAIL light on Ext Panel and AC GND SER Bus, GND Service TRU and DC GND HDLG Bus will be powered.
On engine start, when does engine generators normally come online?
when voltage and frequency are within predetermined limits, the GCU connects the generator to the line.
What is an IDG?
Integrated drive generator.
What is a GCU and what does it do?
Generator Control unit, connects the generator when ready to the line and disconnects Generators from the line when a failure is detected.
If an IDG overheats, what happens and what indication do you get?
Alert 1, IDG TEMP light on MDFU. GCU isolates the Generator.
Is the APU generator equipped with a constant speed drive?
No
If external AC power is online and parameters go out of limits, what will happen?
The Ground Power Control Unit (GPCU) automatically disconnects the external power.
From which generators do AC buses 1 and 2 normally receive power?
Gen 1 and Gen 2.
When is the automatic AC cross-tie inhibited?
by the AUTO AC XTIE p/b.
What buses remain powered after the ESS+EMERG PWR ONLY push button us pressed?
only ESS and EMER buses are powered.
What are the power source priorities for the ESS AC Bus?
Gen 1, Gen 2 and then APU.
From where can the EMER AC bus obtain power?
from the ESS AC Bus, if fails, then from Batteries via a inverter
When is the galley power shed automatically>
during single Gen operations
You are airborne and generator 1 goes offline. The APU gen is no available. What happens? and if the APU generator is available?
If GEN 1 goes offline, Gen 2 via bus ties will power entire system.
If APU is available, it will power AC Bus 1.
What happens if a TRU fault occurs? What might the fault be?
TRU automatically disconnect in case of overheat or reverse current. Alert 2 will appear. Have to manually tie DC bus tie.
What does the dual DC bus supply and for what purpose?
uninterrupted power source for the light dumpers, anti skid and speed brakes.
What can be powered by the batteries alone?
EMERG DC and AC only.
How can the DC buses be tied together?
Via DC Xtie p/b.
If the ESS TRU becomes inoperative, where does the ESS DC get its power from?
TRU 1 via DC Bus 1.
Where does the EMER DC Bus get its power from?
ESS AC Bus via ESS TRU.
What does the DC ground handling bus supply?
pax door, Fueling panel, towing hydraulic service and engine starter valve.
What can be powered from the external DC and what indications do you get?
The DC GND SER bus, no indications.
