Electrical Flashcards
What are the 3 primary sources of electrical power?
AC, DC, external power
Which MCBs are on the pilot side circuit breaker panel? Copilots?
Essential DC bus MCBs Main and avionics DC bus MCBs
How many ECBUs are there? How many AC and DC ECBs are in each unit?
14 24 DC / 15 AC
What is the AC power system comprised of? What is it powered by?
6 AC buses and 2 AC inverters powered by an external power supply, engine generators, and/or APU generator
What powers the main avionics AC inverter and what does the inverter power in return?
Avionics DC bus Main avionics AC bus
What powers the essential avionics AC inverter and what does the inverter power in return?
Isolated DC bus essential avionics AC bus
What does the external power supply?
all 12 AC and DC buses
What are the engine generators rated at? How are they cooled?
115V 3 phase oil-cooled
What is the APU generator rated at? How is it cooled?
115V 3 phase air-cooled
What is the DC power system comprised of?
6 DC buses 4 transformer rectifiers bus-tie relay 2 batteries
What do the transformer rectifiers do?
convert AC power to DC power
What does the bus-tie relay do?
separates the isolated DC and avionics DC buses from each other when the APU is not online
What are the two batteries? What do they supply power to?
Utility battery - utility battery bus and isolated dc bus Avionics battery - avionics battery bus and avionics dc bus
What are the batteries rated at?
lead-acid 24 Vdc, 35 amp/hour
Are the batteries interchangeable?
Yes, they are identical and interchangable
What are the 6 AC buses?
LH, RH, essential, main, essential avionics, main avionics
Which buses are powered by any of the engine-driven generators?
Both the essential ac bus and the main ac bus
What buses are powered by the APU if the APU is the only source of power?
essential ac and main ac
What bus is ALWAYS powered by the APU?
essential ac
If one generator is failed, which generator picks up the load? If both are failed on the same wing?
generator on the same wing symmetrical generator on opposite wing
What are the inverters rated at?
115 Vac
The inverters supply how much power?
26 Vac
Can the APU and external power supply power at the same time?
No. Interlocks allow either or to supply power
During ground operations, do not attempt to start the APU if the battery voltage is less than what? In-flight? What happens if you do, both on the ground and in-flight?
22 Vdc, may cause the battery to overheat 23 Vdc, a voltage transient may cause an unrecoverable loss of essential equipment including MC, displays, and other mission critical battery powered systems.
If a differential fault has occurred, the generator cannot be reset until when?
DC power has been removed from the GCU generator has stopped rotating generator control circuit breaker is pulled and reset
What does the Generator Control Unit do?
monitors the generator frequency and voltage and regulates the power output to the bus
A GCU can fail without generating an ACAWS. When should you suspect a latent GCU failure?
when 115 Vac is indicated on all phases with the % LOAD indicating zero when the generator should be providing power to the electrical system
What TRs does the essential ac bus power?
1 and 2
What TRs does the main ac bus power?
3 and 4
Which TRs power the essential DC bus?
1 and 3
Which TRs power the main DC bus?
2 and 4
What are the 6 DC buses?
essential, main, isolated, avionics, utility battery bus, avionics battery bus
The TRs convert AC power into how much DC power?
28 Vdc
When should you pull MCBs?
only during emergencies or maintenance
