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