Electric

Question 1

Volts and Amps of Batteries

Answer 1

24 volt DC Power

40 amp

Question 2

DC power sources

Answer 2

2 dc starter generators
2 transformer rectifier units
1 apu dc generator

Question 3

Hot Battery Bus is connected to what

Answer 3

STBY battery bus

Question 4

Bat location

Answer 4

Main and Aux in lower left nose compartment

Standby in upper left nose compartment

Question 5

What bats able to assist engine starts?

Answer 5

Main and Aux

Question 6

Can bats be used in flight?

Answer 6

All three bats can be used in flight (in emerg) to supply backup power to DC ess busses for 45 mins.

Question 7

What is on the hot bat bus?

Answer 7

Clock, Bat master, bat refuel, squibs, fuel and hyd sov, cargo fire, apu squib, boarding lights, dome lights, pa emerg power

Question 8

What does the bat master switch do

Answer 8

closes three contactors to directly connect all three batteries to the left and right dc essential buses

Question 9

What is the batt master switch powered by?

Answer 9

STBY BATT

Question 10

How does the elect system automatically reconfig itself in response to various power source failures and bus faults?

Answer 10

Electrical Power Control Unit EPCU (behind capts seat)

Question 11

How are the batts charged?

Answer 11

2 WAY POWER FLOW from the DC main bus that its connected to

except the stby bat which is a one way power flow from the left dc main bus for battery charging only

Question 12

What temp will you get a master warning for batt overheat

Answer 12

71C

65C for red indication on electrical page

Question 13

What does the main bus tie switch do?

Answer 13

Connects the L main DC bus to the R main DC bus

Question 14

Max bat load for second engine start

Answer 14

.4

Question 15

The EPCU will auto disconnect the ext pwr when voltage

Answer 15

exceeds 31 volts

drops below 22 volts

Question 16

How are DC starter gens cooled

Answer 16

air cooled

Question 17

When does the GCU convert from starter mode to gen mode?

Answer 17

50% NH

Question 18

Dc gens are rated for how many amps?

Answer 18

400 amps each

Question 19

Can an EPCU automatically take a gen offline?

Answer 19

yes

Question 20

What do TRUs do and where are they located.

Answer 20

2 TRUs convert 115 volt AC into 28 volt DC power, located in upper right nose bay

Question 21

How are the TRUs cooled?

Answer 21

Air, self contained fans

Question 22

When are the AC gens powered?

Answer 22

Condition levers at min/max range

Question 23

How many DC bus ties and controlled by what?

Answer 23

4 bus ties controlled automatically by EPCU or bus tie switch

Question 24

How many DC power sources can fail for the EPCU to maintain power to all six DC buses

Answer 24

The EPCU is able to maintain power to all six DC buses when as many as two (of four) Dc power sources fail. If more than two fail automatic load shedding occurs

Question 25

EPCU Logic

Answer 25

can only close ONE bus tie per good DC power source

the EPCU will always close the min number of bus ties to provide power

Question 26

How are the AC gens cooled and location

Answer 26

2 oil cooled ac gens on prop reduction gearbox supply 115 volt variable freq