Electrics

Question 1

Battery Discharge​ (BAT​ DISCHARGE) Light

Answer 1

Illuminated (amber) –​ with​ BAT​ switch ON,​ excessive battery discharge detected

Question 2

TR UNIT​ Light

Answer 2

Illuminated (amber) –​
•​ on the ground – any TR has failed.​
•​ in flight –​•​ TR1 failed; or​
•​ TR2 and TR3 failed

Question 3

Electrical (ELEC) Light

Answer 3

Illuminated (amber) – a fault​ exists​ in DC​ power system or standby power system.​
Note:​ Operates only​ with airplane​ on ground

Question 4

STANDBY​ Power​ Off (PWR OFF) Light

Answer 4

Illuminated (amber) –​ one or more of the following busses are unpowered:​
•​ AC standby bus​
•​ DC standby bus​
•battery​ bus

Question 5

Generator Drive (DRIVE) Lights
Illuminated (amber).

Answer 5

Integrated drive generator (IDG) low oil pressure caused by one of the following:
• IDG failure
• engine shutdown
• IDG automatic disconnect due to high oil temperature
• IDG disconnected through generator drive DISCONNECT switch

Question 6

STANDBY POWER Switch
AUTO (guarded position) -

Answer 6

In flight, or on the ground, and AC transfer busses powered:
• AC standby bus is powered by AC transfer bus 1
• DC standby bus is powered by TRI, TR2 and TR3
In flight, or on the ground, loss of all AC power
• AC standby bus is powered by battery through static inverter
• DC standby bus is powered by battery
• Battery bus is powered by battery.

Question 7

STANDBY POWER SWITCH
OFF (center position) -

Answer 7

• STANDBY PWR OFF light illuminates
• AC standby bus, static inverter, and DC standby bus are not powered.

Question 8

STANDBY POWER Switch
BAT (unguarded position) -

Answer 8

• AC standby bus is powered by battery through static inverter
• DC standby bus and battery bus are powered directly by battery

Question 9

TRANSFER BUS OFF Lights
Illuminated (amber) -

Answer 9

Related transfer bus is not powered.

Question 10

SOURCE OFF​ Lights​Illuminated (amber) –

Answer 10

No source has been manually selected to power the related ​transfer bus, or the manually selected source has been disconnected.​
•​ if a source has​ been selected to power the opposite transfer bus, both ​transfer busses are powered

Question 11

Generator​ Off Bus (GEN OFF​ BUS) Lights​Illuminated (blue) –

Answer 11

IDG is not supplying power​ to the related transfer​ bus

Question 12

Generator​ (GEN) Switches

Answer 12

Three position​ switch, spring–loaded​ to​ neutral.​
OFF – disconnects IDG from​ related AC​ transfer bus by​ opening generator circuit ​breaker.​
ON – connects IDG to​ related AC transfer​ bus by disconnecting previous​ power ​source and closing generator circuit breaker

Question 13

BUS TRANSFER Switch​ - AUTO (guarded position)

Answer 13

BTBs operate automatically to​ maintain power to​ AC ​transfer busses from any operating​ generator or external power.​
•​ DC cross tie relay automatically​ provides normal or​ isolated operation​ ​as required.​

Question 14

BUS TRANSFER Switch​ - OFF

Answer 14

isolates​ AC transfer bus 1 from AC​ transfer bus 2 if one IDG is supplying ​power to both AC transfer busses.​
•​ DC cross tie relay opens to​ isolate DC bus 1 from DC bus 2.​
•​ Inhibits TR3​ input from connecting to AC transfer bus 1

Question 15

APU Generator​ Off Bus (GEN OFF​ BUS) Light​

Answer 15

Illuminated (blue) – APU is running​ and not powering a bus

Question 16

APU Generator​ (GEN) Switches​ - OFF
(Three position​ switch, spring–loaded​ to neutral.)

Answer 16

​APU generator powering both AC transfer busses​
•​ moving a single APU​ GEN​ switch to​ OFF illuminates related​ ​SOURCE OFF light. APU continues to power AC​ transfer busses​
•​ subsequently​ moving other APU GEN switch​ to OFF disconnects ​APU generator from​ tie bus and​ removes APU power from​ AC ​transfer busses​

APU generator powering one AC transfer bus; IDG powering​ one AC ​transfer bus
​•​ moving related APU​ GEN switch to​ OFF disconnects APU generator ​from tie bus and AC transfer bus.​ IDG powers​ AC transfer busses.​

Question 17

APU Generator​ (GEN) Switches. - ON

Answer 17

Neither AC transfer bus powered by IDG​ –​ moving a single APU GEN ​switch​ to 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.​

Both​ AC​ transfer busses powered by IDGs​ – 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 18

Primary electrical​ power is provided by?

Answer 18

Two engine​ integrated drive generators ​(IDGs)​ which supply three-phase, 115​ volt, 400hz AC

Each ​IDG supplies its own bus system in​ normal operation and​ can​ also​ supply essential ​and non-essential loads of the opposite side bus system​ when one IDG is ​inoperative

Question 19

What supplies ​ ​DC power.

Answer 19

Transformer rectifier (TR) units and a battery/battery charger supply DC power.

The battery also provides backup power for the AC and DC standby ​system.

Question 20

Can you parallel power source?

Answer 20

AC - No
DC - Yes (Cross tie bus relay closed)

Question 21

The standby system provides 115V​ AC and 24V​ DC power to essential systems ​in the event of loss of all engine or APU–driven​ AC​ power.​ The standby​ power ​system consists of:

Answer 21

•​ static inverter
​•​ AC standby bus​
•​ DC standby bus​
• battery​ bus​
•​ hot​ battery bus​
•​ switched hot​ battery​ bus​•​ main battery