Electrical Flashcards
What are the 5 AC buses?
AC Bus 1 and 2
AC ESS Bus
AC Standby Bus
AC Gnd Serv Bus
What are the 8 DC buses?
DC Bus 1 and 2
DC ESS Bus 1, 2 and 3
Hot BATT Bus 1 and 2
DC Gnd Serv Bus
What is the primary source of AC power and how does it work?
AC power provided by engine-driven IDG (Integrated Drive Generators)
Each IDG (located in accessory gear box) consists of a CSD (constant speed drive) giving constant output speed to a 115VAC, 400Hz, 3-phase, 40kVA generator.
In normal operation, how is the AC ESS bus powered?
By AC Bus 2
What are the 2 secondary sources of AC power?
AC GPU
AC from APU GEN
What power does the RAT provide?
Ram Air Turbine
115VAC, 400Hz, 3-phase, 15kVA power
No altitude restriction for RAT deployment
Constant generator speed is obtained through an automatic variable pitch mechanism
Airspeed limitation for RAT?
No strict limitation, but below 130kts, DC power is provided by batteries.
Above 130kts, DC power is provided to DC ESS buses by TRU ESS, powered by AC ESS bus
What is AC power source priority?
- Associated IDG
- APU
- GPU
- Opposite IDG
What is NBPT system?
No-Break Power Transfer system.
Momentary parallel AC power between two sources, to avoid electrical cuts or transients.
On ground only, duration is in milliseconds.
What is recommended to avoid power interruptions?
Wait 30 sec. after N2 is stabilized on one engine before shutting APU off or disconnect GPU
What are the primary sources of DC power?
TRUs : Transformer Rectifier Units
Converting 115VAC to 28VDC at 300A.
What is the secondary source of DC power?
Two 24VDC, 27Ah batteries.
BATT 1 is located in FWD electronics bay
BATT 2 is located in AFT electronics bay
How much time of DC essential loads do batteries provide?
Approx. 10 min.
Why is BATT 1 On/Off and BATT 2 is Auto/Off?
Because BATT 2 knob also automatically controls the tie contactor that powers the APU Start bus
In case BATT 2 is unavailable, what is the other source of DC power for APU Start bus?
DC GPU.
Not depicted on Electrical Panel, only in the Electrical synoptic page (MFD).
Only available for this bus and for APU start. Won’t provide DC power to the rest of the system.
