Electrics Flashcards
What are the AC power sources?
- Two Engine Generators
- One APU Generator
- Emergency Generator
- External Power
- Static Inverter (last resort. Converts battery 1 DC power to 115 VAC power)
What are the DC Power Sources?
- 2 x Transformer Rectifiers (convert AC to 28V DC)
- 1 x Essential Transformer Rectifier (will power the emergency DC system from the emergency RAT generator if the other 3 x gens fail or the stars fail)
- 2 x batts as last resort
Priority for electrical power sources?
- Engine Generators
- External Power
- APU Generator
- RAT / Emergency Generator
- DC batteries
What is the GCU and GAPCU and what do they do?
- Generator Control Unit. They control and monitor the engine gens
- Ground and Auxiliary Power Control Unit. Controls the APU generator and external power. Allows no break power transfer when required
(Note: GCU and GAPCU control which power source takes priority via generator line contractors (GLC)
What are the three types of circuit breakers and what do they mean?
Green - monitored
Black - not monitored
Red - reset by maintenance
What is an IDG?
Integrated Drive Generator. A generator which is driven at a constant speed by an integrated drive.
Provides 3 phase 115 and 200V AC at 400Hz (90KVA)
AC Bus System. What do AC bus 1 and AC bus 2 do?
AC Bus 1.
Gen 1 powers AC Bus 1 - which supplies TR1 and AC ESS bus
AC Bus 2
Gen 2 powers AC Bus 2 - which supplies TR2 And AC GND / FLIGHT BUS
What does the BUS TIE button do?
It allows AC BUS 1 And AC BUS 2 To be powered by different power sources
Usually is auto mode. If only one power supply, auto switch means commands to close a bus tie in order to ensure power to both AC BUS 1 and AC BUS 2
How is the AC ESS bus powered in the event of failure of AC BUS 1?
It is powered via AC BUS 2 automatically2 or by selecting the AC ESS FEED push button.
What is the ESS SHED BUS?
Power led by the AC ESS BUS
will shed automatically if only battery power is available
What is a TR?
Transformer rectifier. Converts AC power to DC power
Each TR controls its respective contactor (open or closed)
How many TRs are they and where are they powered from?
- 2 x TR and 1 x ESS TR
A) AC BUS1 powers — TR1 —- DC BUS1
B) AC BUS2 powers — TR2 — DC BUS 2
C) Backup. EMER GEN powers both — AC ESS BUS and ESS TR / DC ESS BUS
How many batteries are there and how are they connected to the ELEC system?
2 batteries (23 Amp hour) connected as follows:
BAT1 - HOT BUS1 - BCL (contactor is open or closed) - DC BAT BUS
Symmetrical for BAT2
What do the BAT1 and BAT2 pb’s do?
They control the BCL (contactor) to either connect or remove the battery from DC BUS 1.
They are connected to DC BAT BUS if battery levels are low (ie to charge them) or for APU start
NOTE: the batteries are always connected to the hot busses
What is a static inverter and what does it do?
The Static Inverter transforms DC power from BAT 1 to single phase 115 AC (1KVA) power for the AC ESS BUS
activated temporarily until the RAT (Emergency Generator) comes online and takes over powering the electrical network
How is the DC ESS BUS powered in normal and abnormal operation?
Normal
By the DC BAT BUS via the ESS DC TIE CONTACTOR
Abnormal
By either:
- ESS TR (powered by Emergency Gen or AC ESS bus)
- BAT 2
What does the MAINT BUS switch do?
TBC
Electrics. When does the RAT auto extend and what does it do?
- Loss of AC BUS 1 and 2; and
- Above 100kts
It provides blue system Hyd pressure which drives the emergency generator at a constant speed
What happens if lose AC BUS 1 and 2 and the RAT is unavailable (e.g for 8 seconds whilst the RAT deploys)?
- Utilises battery power and static inverter (BAT1 powers AC ESS BUS. BAT2 powers DC ESS BUS)
- System will shed the AC and DC ESS SHED busses
How do you know if the RAT is extended and the Emergency Generator is running?
Shown on the E/WD
Electric cockpit prep. When select BAT1 and BAT2 off (and then back on) - what are you checking for on the ELEC ECAM PAGE?
- That both battery charged and currents decrease to below 60A within 10 seconds
Notes batteries should be above 25.5V
How do you transfer from external power to APU power?
Press EXT PWR pb (this automatically then connects to the APU gen
Electric abnormal. GEN1 Fail. What happens automatically?
- GEN2 Supplies full system (I.e via AC BUS 1 and AC BUS 2)
- Main Galley electrics are shed (to save power)
- ECAM Master Caution (triggers a reset action)
- If reset fails - start APU GEN (which would then takeover powering AC BUS 1)
- Main galley electrics back online (as have 2 x Gen again)
How many ways of generating AC Power?
5 broken down as follows:
- GEN1
- GEN2
- APU
- Emergency Generator
- Static inverter
What does Static Inverter do?
Converts DC to AC
When do batteries connect to the DC BAT BUS normally?
For a charging cycle
What are we checking for re preliminary battery checks?
- Batteries are above 25.5V
Are the batteries always connected to the Hot Bat Bus?
Yes
What is the capacity of the batteries?
23AmpH each
24V each (but remember - answer in final exam re volts is likely to be related to DC system - answer 28V)
How is the AC ESS BUS powered normally?
Via AC BUS 1
How is the AC ESS BUS powered in abnormal (if AC BUS 1 fails)
Via AC BUS 2
Guarded IDG guarded switch. Yellow fault light. What is the cause?
- IDG temp issue
- Low oil pressure
Is the Emergency Gen / Rat automatically deployed
- Yes if above 100kts and double failure of AC BUS 1 and AC BUS 2
What are the IDG electric power outputs ?
3 phase, 115/220V, 400Hz, 90KPA
What is the APU electric output?
Same as IDG (3 phase, 115/220V, 400Hz) (check KPA)
Emergency generator electric power output?
3 Phase, 115/220V, 400Hz, 5KVA
Power output of Static Inverter?
Single phase, 115V, 400hz, 1KVA
The TR converts 115/200V AC into…:
28V DC
