Electric Flashcards
Volts and Amps of Batteries
24 volt DC Power
40 amp
DC power sources
2 dc starter generators
2 transformer rectifier units
1 apu dc generator
Hot Battery Bus is connected to what
STBY battery bus
Bat location
Main and Aux in lower left nose compartment
Standby in upper left nose compartment
What bats able to assist engine starts?
Main and Aux
Can bats be used in flight?
All three bats can be used in flight (in emerg) to supply backup power to DC ess busses for 45 mins.
What is on the hot bat bus?
Clock, Bat master, bat refuel, squibs, fuel and hyd sov, cargo fire, apu squib, boarding lights, dome lights, pa emerg power
What does the bat master switch do
closes three contactors to directly connect all three batteries to the left and right dc essential buses
What is the batt master switch powered by?
STBY BATT
How does the elect system automatically reconfig itself in response to various power source failures and bus faults?
Electrical Power Control Unit EPCU (behind capts seat)
How are the batts charged?
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
What temp will you get a master warning for batt overheat
71C
65C for red indication on electrical page
What does the main bus tie switch do?
Connects the L main DC bus to the R main DC bus
Max bat load for second engine start
.4
The EPCU will auto disconnect the ext pwr when voltage
exceeds 31 volts
drops below 22 volts
How are DC starter gens cooled
air cooled
When does the GCU convert from starter mode to gen mode?
50% NH
Dc gens are rated for how many amps?
400 amps each
Can an EPCU automatically take a gen offline?
yes
What do TRUs do and where are they located.
2 TRUs convert 115 volt AC into 28 volt DC power, located in upper right nose bay
How are the TRUs cooled?
Air, self contained fans
When are the AC gens powered?
Condition levers at min/max range
How many DC bus ties and controlled by what?
4 bus ties controlled automatically by EPCU or bus tie switch
How many DC power sources can fail for the EPCU to maintain power to all six DC buses
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
EPCU Logic
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
How are the AC gens cooled and location
2 oil cooled ac gens on prop reduction gearbox supply 115 volt variable freq
