ELECTRICAL (ASM) Flashcards
What sources provide electrical power supply
DC Power
AC Power
What is the DC power system comprised of
Four independent generators (28V DC / 400 A)
One APU starter generator (28V DC / 400 A)
Two Nickel-Cadmium (24V DC / 44AH / 1 hour rate)
One lead-acid backup battery (24V DC / 5AH / 10 hour rate)
External Power source
How is DC power converted into AC power
Single phase static inverter
Purpose of the EDL and GCU
Perform system management, detects system failures and are automatically isolated de-energizing some buses
Engine 1 drives what generators
1 and 3
The left network operates what buses
DC Bus 1
Essential DC Bus 1
Shed DC Bus 1
Hot Bus 1
How is Battery 1 charged
Charged by generators connected to DC Bus 1
Engine 2 drives what generators
2 and 4
How are both networks interconnected
Through Bus Tie Contactors (BTC)
What happens if an over voltage is detected
Associated GCU de-energizes the generator and disconnects it from the bus
What happens if a generator exceeds 400A
Manual load shedding is required
If no action is taken, the system will be isolated and some buses may be de-energized
What does the GPU have priority over
Batteries and generators
What do the batteries supply
Essential loads in case of in-flight failure of all generators or both engines fail with no APU
How long can both batteries supply essential power for
40 minutes (3 APU start attempts)
What battery supplies power for APU
BATT 2
Does the GPU charge the batteries?
No
Purpose of the backup battery
Provides stabilized power for operation of the GCU protective function
Where are the generators installed
Two installed on each engine accessory gerbox
What controls the generators
GCU
When do the generators come online
56.4% N2
What controls the APU Starter Generator
Dedicated GCU
What does the APU generator supply power to
DC Bus 2
What generator can the APU generator replace
Any inoperative left network generator
After start, automatically any inop engine driven generator
When is the APU available to provide power to the electrical system
95% RPM +7 seconds
Sources to start APU
GPU
BATT 2
BATT 2 assisted by main generator
Can BATT 1 be used to start APU
No, it is isolated to prevent voltage fluctuation
EDL 1 and EDL 2
DC Bus 1, Shed DC Bus 1, Essential DC Bus 1, Hot Bus 1
DC Bus 2, Shed DC Bus 2, Essential DC Bus 2, Hot Bus 2
Purpose of the central DC Bus
Connects APU or GPU to load buses through BTC
When are the DC Buses energized (on the ground)
If one of the following occurs;
3 generators
GPU
1 generator, shed bus OVRD
DC Distribution
5/4 Generators: 2 Isolated Networks
3: Both networks interconnected through BTC
1/2: Both networks interconnected through BTC, shed bus de-energized
0: Batteries provide essential power
AC System provides power to
TCAS
GPWS
Windshear
