Electrical Flashcards
Where does the AC power normally come from
AC power can be supplied by two engine-driven generators, an APU-driven generator, and an external power source.
Where does the DC power normally come from
DC power is supplied by Transformer Rectifier Units (TRU) 1, 2, ESS, and Ground Service, which are powered by the respective AC bus.
What buses does the AC normally supply
AC buses 1&2, ESS AC BUS, EMER AC BUS, AVIONICS TRANSFER BUS, GALLEY BUSES 1&2, AC GROUND SERVICE BUS
What buses does the DC normally supply
DC BUSES 1&2, DUAL DC BUS,ESS DC BUS, EMERDC BUS, DC GROUND SERVICE BUS, DC GROUND HANDLING BUS
If all AC generator power is lost , what power is still available
Only battery power is available
What alert is presented in this situation, where will the alert be shown
AC supply on the SAP
How long would you expect the batteries to last if you loose all generators
30 mins or 60 mins respectively
And 1 APU start attempts
On the ground how can the ground handling and ground service buses be powered
DC Ground Service Bus The AC ground service bus supplies, via a ground service TRU, the DC ground service bus. When the AC power is not available, the DC ground service bus can be powered by an external DC power source. DC Ground Handling Bus The AC ground service bus supplies, via the Ground Service TRU the DC ground handling bus. When no AC power is available the DC ground handling bus is supplied directly by the batteries. The ground handling bus supplies power to:
AC bus 2 supplies AC ground service bus
When external AC is plugged in, but not switched on what is powered and what indications would you get
When AC external power is connected and within limits, the AVAIL light in the external power p/b is on, the AC GROUND SERVICE light at the connector is on, and the AC ground service bus is energized.
On engine start, when do engine generators normally come online
When voltage and frequency are withinpredeterminedlimits,theGCUautomaticallyconnectsthegeneratortothelineandautomaticallydisconnectsthegeneratorfromthelineifafailureisdetected.IftheIDGoiltemperaturebecomesexcessive,analertwillbepresented.Ifthetemperaturecontinuestoriseabovea predetermined value, the IDG will be disconnectedfromtheenginedrive.
What is an IDG
Integrated drive generator
What is a GCU and what does it do
TheIDGoutputiscontrolledbyaGeneratorControlUnit(GCU)andthegeneratorp/b. When voltage and frequency are withinpredeterminedlimits,theGCUautomaticallyconnectsthegeneratortothelineandautomaticallydisconnectsthegeneratorfromthelineifafailureisdetected.
If an IDG overheats, what happens and what indication do you get
IftheIDGoiltemperaturebecomesexcessive,analertwillbepresented.Ifthetemperaturecontinuestoriseabovea predetermined value, the IDG will be disconnectedfromtheenginedrive. You get a level 1 alert and display on MFDU
Is the APU generator equipped with a constant speed drive
The APU generator is notequipped with a constant speed drive since the APUrunsataconstantspeed.
If external AC power is online and parameters go out of limits, what will happen
The Ground Power Control Unit (GPCU)automaticallydisconnectstheexternalpowerfromtheelectricalsystemifitsparametersarenotwithinlimits.
From which generators do AC buses 1 and 2 normally receive power
GEN 1supplies AC bus 1
GEN 2 supplies AC bus 2
When is the automatic AC cross-tie inhibited
TheautomaticcrosstiefunctionforACbuses1and2isinhibitedduringautomaticlandings.. Also inhibited when turned off or faulted
What buses remain powered after the ESS+ EMER PWR ONLY push button is pressed
the essential AC bus and theemergencyACbusremainenergized. ESS DC and EMER DC ALSO
What are the power source priorities for the ESS AC bus
GEN 1 , GEN 2, APU, AC EXTERNAL POWER.
From where can the EMER AC bus obtain power
Under normal power conditions, the EMER AC bus issuppliedbytheESSACbus.IfACsuppliesfailandtheAC buses 1 and 2 and the ESS AC bus become de‐energized,theEMERACbusissuppliedbythebatteriesviaanEMERinverter.
When is the galley power shed automatically
In flight during single generatoroperation, the galley buses are automatically de‐energized.
You are airborne and GEN 1 goes offline. The APU generator is not available, what happens, And if the APU generator is available
Gen 2 will supply AC power tho the whole system
If APU Gen is available then it takes the place of Gen 1 and supplies power to AC bus 1
What happens if a TRU fault occurs, what might the fault be
The TRU’s are automatically disconnected in case of overheat or reverse current. If TRU 1 or 2 should fail an alert will be presented. MCL DOUBLE CHIME AND AMBER FAULT ON MFDU AND LOCAL ALERT.
What does the dual DC bus supply and for what purpose
DC buses 1 and 2 supply the dual DC bus. It provides an uninterrupted power source for the lift dumpers, anti-skid, and speed brake in the event of a DC bus 1 or 2 failure during landing
What can be powered by the batteries alone
The ground handling bus. EMER DC , EMER AC
How can the DC buses be tied together
Manual operation of the DC X-TlE p/b interconnects the DC buses.
If the ESS TRU becomes inop, where does ESS DC get its power from
lf the ESS TRU is inoperative DC bus 1 will supply the ESS DC bus. lf the ESS DC bus becomes de-energized an alert will be presented
Where does EMER DC bus get its power from
The ES AC bus supplies, via ESS TRU, the EMER DC bus. lf the ESS TRU is inoperative the EMER DC bus is automatically supplied by DC bus 1. When no AC power is available the EMER DC bus is automatically supplied by the batteries
What does DC ground handling bus supply
The ground handling bus supplies power to: - Passenger door (if installed) - Fuelling panel - Towing - Hydraulic service panel - Engine starter valve
What can be powered from external DC and what are the indications you get
Adjacent to the external AC receptacle is a 28 V DC receptacle to provide power to the DC ground service bus and the APU starter. There are no controls or indicators in the flight deck related to DC external power
How do you remove power from a PRAM system
Cabin Equipment’ includes components of the MP3 (PRAM) System and the Flightdeck USB Power Outlet System. Power is removed with the checklist item “Galley PWR……OFF”.
Through which bus is the Flightdeck USB power outlet powered
DC BUSES 1&2
