Electrical Flashcards
The AC system is comprised of:
Two IDG's One APU One Inverter One Ram Air Turbine - RAT One AC external power unit
The DC system is comprised of:
Two NiCd batteries
Three TRUs - Transformer Rectifier Units
One DC external power unit
On the AC Electric Panel, the IDG 1/2 switch in the OFF position does what?
Opens the IDG contactor isolating the IDG from the respective AC Bus
How long must one hold the IDG 1/2 in the DISC positon
Must be held in this position for one second to mechanically disconnect the IDG
What does the AC BUS TIES switch do in the 1 OPEN position?
Opens the Bus Tie Contactor - BTC 1 - segregating AC BUS 1 from AC BUS 2
BATTERY 2 supplies power to … ?
HOT BATT BUS 2
In the ON position, BATT 1 is connected to.. ?
the DC ESS BUS 1
BATTERY icons in GREEN
Battery voltages greater than 18 V
BATTERY icons in WHITE
Battery voltages less than 18 V
What is the meaning of IDG 1/2 OIL EICAS Msg?
IDG pressure drops below 140 psi
or
IDG oil temperature reaches 168 deg C
Do not hold the IDG 1/2 knob in the DISC position for longer than.. ?
3 seconds
The IDG will automatically disconnect when… ?
when manual disconnection is not performed with the oil temperature reaching 185.6 deg C
Pushing the AC GPU button connects…
The external power to the AC BUS TIE
The RAT - Ram Air Turbine produces… ?
15 kVa, 115 V AC, 400 Hz
The RAT is deployed whenever… ?
AC power sources are not powering AC buses
How long does it take for the RAT to supply power to the AC ESS BUS
8 seconds
What does the RAT power?
supplies power to the AC ESS BUS
If it takes 8 seconds for the RAT to power the AC ESS BUS, what is the design to prevent total loss of power?
The RAT powers the AC ESS BUS which powers the ESS TRU which powers DC ESS BUSES. To avoid total loss of power for the 8 seconds it takes to power, dedicated standby battery is used as backup power to the DC ESS BUSES and the STANDBY AC BUS
How are primary flight control tasks maintained in the event of loss of electrical power?
RAT drives the ACMP 3A
What is NBPT
No Break Power Transfer
What does the NBPT do?
The No Break Power Transfer allows the momentary paralleling between two AC power sources: The IDG’s, GPU and APU generator in any combination
On the DC Power Panel, what does the DC BUS TIES toggle switch do
Opens both essential tie contactors and a DC tie contactor
The RAT powers what?
AC ESS BUS when AC bus 1 and 2 are not powered
What is the minimum battery voltage
22.5 Volts without action
below that and the battery needs to be warmed up per the SOPM
21.0 limit below which maintenance needs to be called out.
Generators are rated to
40 KVA
the RAT generator is rated to…
15kVa
How long does it take the RAT to power the AC ESS BUS
8 seconds
When is the RAT deployed
When both AC Bus 1 and 2 are not powered
The LED light next to the IDG switches indicate what?
Which IDG needs to be disconnected due to a drop in oil pressure below 25 psi and / or a oil temperature reaches 168 deg C
Automatic IDG disconnect happens when the oil temperature reaches …
186 deg C
During APU start what happens?
BATT 2 is isolated from the network and used to power the APU START BUS exclusively
The RAT drives which ACMP for primary flight control tasks?
Hydraulic Pump 3A
When is the NBPT active
On the ground during power transfers
What do the batteries power during the 8 second delay while the RAT is being deployed
DC ESS BUS
and
STANDBY AC BUS through the static inverter
What do the TRUs do?
convert AC power from the AC BUSES into DC power
What is the min battery temp for APU start?
-20 deg C
If the RAT fails, how long will the battery power be able to provide for essential systems
10 minutes
When will the EICAS message BATT 1/2 OVERTEMP be displayed
Battery temperature reaches 70 deg C for min of 2 seconds
When would you use DC GPU?
Battery unavailable
or
Battery 2 temp less than -20 deg C
What systems are on the AC ESS BUS
AC fuel pump 2
Hydraulic Pump 3A
1 Slat Channel
1 Flap Channel
When the aC bus tie selector knob is selected to the OPEN position, what happens
The selected BUS TIE CONTACTER - BTC is opened, segregating the AC BUS 1/2 from the opposite AC BUS 1/2
What is required before the “AVAIL” light on the GPU button illuminates?
Correct Volts / Amps / Frequency
What happens when the TRU ESS toggle switch is placed in the off position
Isolates the TRU ESS BUS from DC ESS BUS 3
On the ground, what happens when the aircraft is powered only by battery power for longer than 5 minutes
A horn will go off to notify ground personel
What happens when TRU 1 /2 toggle switch is placed in the off position?
Isolates TRU 1 /2 from DC ESS BUS 1 / 2
Why does Battery 2 have an “AUTO” position?
To allow the automatic operation of BATT 2 such as for APU start and BATT 2 being used exclusively for APU Start
What happens when the DC BUS TIES toggle switch is placed in the OFF position?
opens both essential tie contactors and a DC tie contactor
In the OFF position, BATT 1 is connected to what?
The HOT BATT BUS 1 is powered by BATT 1
On the Electrical Synoptic page, what does a green / white battery symbol indicate
Green indicates BATT voltage greater than 18 V
White indicates voltage less than 18 V
Pushing the AC GPU button connects what?
The external power to the AC BUS TIE
What does the Static Inverter do?
converts 28 V DC from the batteries to 115 V AC to supply the STANDBY AC BUS when AC power source is not available. (double check… but the igniters are on this bus)
DC ESS BUSSES are powered through what?
the ESS TRU
What minimum speed is required for the RAT to provide electrical power?
130 KTS
The RAT provides power to what?
The AC ESS BUS
What kind of power does the RAT provide
AC power
How does the RA, if it is AC power, provide power to the DC BUSSES?
DC ESS BUSSES are powered through the ESS TRU
What happens below 130 KTS with the RAT deployed
Load shedding occurs. The DC ESS BUS and the STANDBY AC BUS are powered through the static inverter from the batteries.
What do the TRUs do
Convert 115 V AC power to 28 V DC
When the DC GPU is connected, what is powering the APU START BUS?
The DC GPU powers the APU START BUS, not BATT 2 as is normal condition
What BUS is powered by the RAT
AC ESS BUS
What is the altitude limit for the RAT
There is no altitude limit
How many TRUs are there?
3 TRUs
What is the ICC
Integrated Control Center
How many ICCs are there?
There are 4 ICC - Integrated Control Center Left - LICC Right - RICC Emergency - EICC Auxiliary - AICC
What is the purpose of the Integrated Control Center?
provides power distribution and protection for electrical loads
What is the SPDA
Secondary Power Distribution Assemblies
How are electrical loads and distribution loads monitored and protected?
Through the ICC’s, SPDA’s and Circuit Breaker Panels
What kind of circuit breakers are there?
Thermal and Electronic
What provides for the distribution and control of electrical power?
The ICCs - Integrated Control Center and the SPDAs - Secondary Power Distribution Assemblies
What does each ICC incorporate?
Thermal Circuit Brakers
Line Replaceable Units
Line Replaceable Modules
AD/DC Busses
The AC / DC busses are located where?
Inside their respective ICC - Integrated Control Center
What is the purpose of the SPDA - Secondary Power Distribution Assembly?
Receives power from the ICC and electrical busses and distributes it according to system logic.
The SPDA replaces what found in older aircraft?
Thermal Circuit Breakers and Electromechanical Relays
Where are the thermal CBs located?
Flight Deck side wall and other inside the ICCs in the electronics bay
Where are the electronic CBs located?
Inside the SPDAs in the electronics bays
Can the remote ICC remote CBs be reset?
Only by a mechanic
Can the SPDA remote electronic CBs be reset?
Yes, via the MCDU
Explain the flow of electrical power
The electrical power generated from the IDG, APU or GPU is directed to the ICCs and the electrical busses. From their it is routed through the SPDA and to the electrical systems.
The systems requiring complex logic are connected to the MAUs.
Mostly complete…
Just some in depth emergency power question to go
