ELECTRICAL (ASM)

Question 1

What sources provide electrical power supply

Answer 1

DC Power
AC Power

Question 2

What is the DC power system comprised of

Answer 2

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

Question 3

How is DC power converted into AC power

Answer 3

Single phase static inverter

Question 4

Purpose of the EDL and GCU

Answer 4

Perform system management, detects system failures and are automatically isolated de-energizing some buses

Question 5

Engine 1 drives what generators

Answer 5

1 and 3

Question 6

The left network operates what buses

Answer 6

DC Bus 1
Essential DC Bus 1
Shed DC Bus 1
Hot Bus 1

Question 7

How is Battery 1 charged

Answer 7

Charged by generators connected to DC Bus 1

Question 8

Engine 2 drives what generators

Answer 8

2 and 4

Question 9

How are both networks interconnected

Answer 9

Through Bus Tie Contactors (BTC)

Question 10

What happens if an over voltage is detected

Answer 10

Associated GCU de-energizes the generator and disconnects it from the bus

Question 11

What happens if a generator exceeds 400A

Answer 11

Manual load shedding is required
If no action is taken, the system will be isolated and some buses may be de-energized

Question 12

What does the GPU have priority over

Answer 12

Batteries and generators

Question 13

What do the batteries supply

Answer 13

Essential loads in case of in-flight failure of all generators or both engines fail with no APU

Question 14

How long can both batteries supply essential power for

Answer 14

40 minutes (3 APU start attempts)

Question 15

What battery supplies power for APU

Answer 15

BATT 2

Question 16

Does the GPU charge the batteries?

Answer 16

No

Question 17

Purpose of the backup battery

Answer 17

Provides stabilized power for operation of the GCU protective function

Question 18

Where are the generators installed

Answer 18

Two installed on each engine accessory gerbox

Question 19

What controls the generators

Answer 19

GCU

Question 20

When do the generators come online

Answer 20

56.4% N2

Question 21

What controls the APU Starter Generator

Answer 21

Dedicated GCU

Question 22

What does the APU generator supply power to

Answer 22

DC Bus 2

Question 23

What generator can the APU generator replace

Answer 23

Any inoperative left network generator
After start, automatically any inop engine driven generator

Question 24

When is the APU available to provide power to the electrical system

Answer 24

95% RPM +7 seconds

Question 25

Sources to start APU

Answer 25

GPU
BATT 2
BATT 2 assisted by main generator

Question 26

Can BATT 1 be used to start APU

Answer 26

No, it is isolated to prevent voltage fluctuation

Question 27

EDL 1 and EDL 2

Answer 27

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

Question 28

Purpose of the central DC Bus

Answer 28

Connects APU or GPU to load buses through BTC

Question 29

When are the DC Buses energized (on the ground)

Answer 29

If one of the following occurs;
3 generators
GPU
1 generator, shed bus OVRD

Question 30

DC Distribution

Answer 30

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

Question 31

AC System provides power to

Answer 31

TCAS
GPWS
Windshear