Electrical System

Question 1

BAT DISCHARGE (AMBER LIGHT)

Answer 1

With the BAT switch ON, excessive battery discharge is detected

Question 2

TR UNIT (AMBER LIGHT)

Answer 2

On the ground: Any TR has failed

In flight: TR1 or TR2 and TR3 has failed

Question 3

ELEC (AMBER LIGHT)

Answer 3

A fault exists in the DC power system or the Standby power system. The ELEC light is inhibited in flight

Question 4

BAT (SWITCH)

Answer 4

BAT Switch (OFF) : Removes power from the battery bus and switched hot battery bus when operating with normal power sources available.
Removes power from the battery bus, switched hot battery bus, DC standby Bus, Static inverter and AC standby bus when battery is the only power

BAT Switch (ON) (Guarded Position) : Provides power to the switched hot battery bus
Energizes relays to provide automatic switching of standby electrical system to battery power with loss of normal power

Question 5

DRIVE (AMBER LIGHT)

Answer 5

IDG low oil pressure caused by: IDG failure, Engine Shutdown, IDG automatic disconnect due to high oil temp, IDG disconnected through the generator drive DISCONNECT switch.

Question 6

STANDBY POWER OFF (AMBER LIGHT)

Answer 6

One or more of the following busses are unpowered: AC standby bus, DC standby bus, battery bus

Question 7

STANDBY POWER (SWITCH)

Answer 7

AUTO:
COND: In flight or on the ground and the AC transfer busses powered..
AC standby bus is powered by the AC transfer bus #1
DC standby bus is powered by the TR 1/2/3

COND: In flight, or on the ground, loss of all AC power
AC standby bus is powered by battery through the static inverter
DC standby bus is powered by battery
Battery bus powered by battery

OFF (Center position): STANDBY PWR OFF illuminates and AC standby bus, static inverter, and DC standby bus are not powered

BAT (UNGUARDED POSTION):
AC standby bus is powered by battery through the static inverter
DC standby bus is powered by battery

Question 8

GRD PWR (SWITCH)

Answer 8

OFF: Disconnects ground power from AC transfer buses
ON:
- Removes prev connected power from AC transfer busses
- Connects ground power to AC transfer busses if power quality is correct

Question 9

TRANSFER BUS OFF (AMBER LIGHT)

Answer 9

related transfer bus is not powered

Question 10

SOURCE OFF (AMBER LIGHT)

Answer 10

No source has been manually selected to power the related transfer bus or the manually selected source has been disconnected
Note: if the other transfer bus is powered, both transfer busses will be powered via the BTB

Question 11

GEN (SWITCHES)

Answer 11

OFF: Disconnects IDG from the respective AC transfer bus by opening generator circuit breaker
ON: Connects IDC to the respective AC transfer bus by disconnecting previous power source and closing the generator circuit breaker

Question 12

BUS TRANSFER (SWITCH)

Answer 12

Auto (guarded position) :

• BTB’s operate automatically to maintain power to AC transfer busses from power source.
• DC cross tie relay automatically provides normal or isolated operation as required

OFF :

• isolates the AC transfer bus 1 from AC transfer bus 2 if only 1 IDG is supplying power to both AC transfer buses
• DC cross tie relay opens to isolate the DC bus 1 from DC bus 2

Question 13

APU GEN (SWITCHES) (OFF)

Answer 13

Scenario: APU generator powering both AC transfer buses

• moving a single APU GEN switch to the OFF illuminates related SOURCE OFF light. APU continues to power both AC transfer busses
• Subsequently moving the other APU GEN switch to OFF disconnects APU generator from the tie bus and removes APU power from AC transfer buses
• If 1 APU GEN ON and 1 IDG GEN are powering the AC transfer busses moving the APU GEN OFF will result in the 1 IDG powering both AC transfer busses

Question 14

APU GEN (SWITCHES) (ON)

Answer 14

Scenario: Neither AC transfer bus powered by IDG - moving a single APU GEN switch ON:

• connects both AC transfer busses to the APU generator
• disconnects external power, if connected
• opposite SOURCE OFF light illuminates until the other APU GEN switch is moved to ON

Scenario: Both AC transfer busses powered by IDG’s - moving an APU GEN switch ON:

• powers the related AC transfer bus from the APU generator
• other AC transfer bus continues to receive power from the IDG

Question 15

Electrical System is primarily powered by ?

Answer 15

2 engine IDG’s

Question 16

An IDG supplies what kind of power ?

Answer 16

3 phase, 115 volt, 400 cycle alternating current (AC)

Question 17

What supplies DC power ?

Answer 17

TRU (28 volt) and the main battery / battery charger

Question 18

What supplies backup power for the AC / DC standby system

Answer 18

The main and aux batteries

Question 19

External power is what kind of power

Answer 19

AC

Question 20

What does the AC power system consist of ?

Answer 20

transfer bus, a main bus, two galley buses, and a ground service bus

Question 21

What supplies power to the AC standby bus

Answer 21

Transfer bus 1

Question 22

Automatic Load shedding (engine generators)

Answer 22

For single GEN operation: galley and main bus on transfer bus 2 shed first followed by galley and main bus on transfer bus 1

Question 23

TRU’s convert (blank) AC into ?

Answer 23

TRU’s convert 115 volt AC to 28 volt DC

Question 24

TRU #1 gets power from ?

Answer 24

AC Transfer bus #1

Question 25

TRU #2 and #3 get power from ?

Answer 25

AC Transfer bus #2

Question 26

TRU #3 has back up power from ?

Answer 26

AC Transfer bus #1

Question 27

Under normal conditions what do TRU #1/2/3 power ?

Answer 27

TRU #1/2 power the DC bus #1/2 and the DC standby bus | TRU #3 power the battery bus and serves as a back up power source for TRU #1/2

Question 28

What kind of batteries ? How many ?

Answer 28

2 batteries (main and aux) , 24 volt nickel-cadmium batteries

Question 29

How long can the batteries provide standby power?

Answer 29

60 mins when fully charged

Question 30

Battery voltage range

Answer 30

22-30 volts

Question 31

What DC busses are powered from the battery following a loss of both generators?

Answer 31

Battery bus DC standby bus hot battery bus switched hot battery bus

Question 32

The standby system provides what kind of power?

Answer 32

115 volt AC and 24 volt DC to essential systems in the event of loss of all engine or APU driven AC power

Question 33

What does the Standby power system consist off?

Answer 33

``` Static inverter AC standby bus DC standby bus battery bus hot battery bus switched hot battery bus main battery aux battery ```

Question 34

The static inverter converts what power

Answer 34

24 volt DC from the battery to 115 volt AC to supply the AC standby bus during loss of normal electrical power

Question 35

The static inverter is controlled by the ?

Answer 35

Standby power switch and the battery switch on the overhead panel