Electrical Flashcards
How many independent electrical systems are on the airplane? Why?
ASM 6.1.1
- 2 independent networks
- Redundancy
What components power the AC system?
ASM 6.1.1
- 2 Integrated Drive Generators (IDG) (40 KVA)
- Auxiliary Power Unit (APU)
- Inverter
- Ram Air Turbine (RAT) (15 KVA)
- AC GPU receptacle
What components power the DC system?
ASM 6.1.1
- 2 NiCad batteries
- 3 transformer rectifier units (TRU)
- DC GPU receptacle
List all the DC buses
ASM 6.8.2.4
- GND service bus
- APU start bus
- 2 HOT BAT buses
- 2 DC buses
- 3 DC ESS buses
What is the source priority order for powering the AC main buses?
ASM 6.8.3
- Onside
- Inside (APU GEN)
- Outside (GPU if connected)
- Cross-side (Opposite IDG)
How does the IDG maintain a stable power output?
A constant speed drive (CSD) attaches the IDG to the AGB (accessory gear box)
What monitors and controls the IDGs?
ASM 6.3.2.1
Each has a generator control unit (GCU)
If only 1 IDG is on, what powers the other side? What if you start the APU? What would power it?
- IDG will power both sides through BTC 1
- APU will power the right side (system 2) through BTC 2
Are the IDG icons on the MFD always in view even when the IDGs are not powered?
Almost always. They become 3 dashes if invalid or out of range. Otherwise they are always in view.
Can one IDG power the entire electrical system?
Yes
Does the IDG have its own oil supply? If yes, can you see it’s quantity?
Yes, No
On the electric control panel, the amber lights near the IDG control knob indicates what?
Which IDG must be disconnected and its associated EICAS message
What are three reasons for the IDG disconnect light to illuminate?
- High oil temperature
- Low oil pressure
- Annunciator test button
If an IDG is mechanically disconnected can it be reconnected on the ground or in flight by the flight crew?
No, this is a maintenance function.
What indication would you get with an IDG low oil pressure or high oil temperature?
An amber LED next to the associated IDG switch and an associated EICAS IDG 1(2) oil illumination
During “normal operation” will a failed IDG de-power the respective AC bus?
No
What happens when the IDG selector knob is in AUTO, OFF or DISC?
AUTO: Allows the automatic operation of the electrical system. It closes the IDG contractor, connecting the IDG to its respective AC bus.
OFF: The generator is de-engergized and the IDG contractor is opened isolating the IDG from the respective AC bus
DISC: must be held in this position for one second to mechanically disconnect the IDG
What is the primary purpose of the AC generators?
To power the AC BUSs and the AC ESS BUS which…
Power the 3 transformer rectifier units TRU 1, 2 and ESS
What is primary and alternate sources of power for the AC ESS BUS?
Primary is the AC BUS 2. ALT is AC BUS 1 (and the RAT when both AC BUSs 1 and 2 are not powered)
What is the normal and alternate source of power for the AC standby bus?
Normal is the AC ESS BUS and the alternate is the AC inverter
State the source priairoty for powering the AC main buses
Respective IDG
Which AC source has priority, the APU or GPU
APUhas priority and will automatically switch when the API is ip and running
Will the AC APU icon always be in view on the MFD>
No, only when the APU is available (3 seconds after 95%)
What is the purpose of the transformer rectifier units?
To convert 115 VAX to 28 VDC
What happens when the TRU 1 (2) and TRU ESS switches are in AUTO?
AUTO allows automatic operation of the electrical system. TRU 1 and 2 connect to its respective DC BUS, TRU ESS connects to the ESS BUS 3
What does the OFF position of TRU 1 and 2 do?
Isolates the TRU from its respective DC BUS
What does the OFF position of TRU ESS do?
Isolates the TRU from ESS BUS 3
During normal operations, TRU 1 supplies power to what?
DC BUS 1, DC ESS BUS 1, DC ground service bus, HOT BATT 1, and BATT 1 charging
During normal operations TRU 2 supplies power to what?
DC BUS 2, DC ESS BUS 2, HOT BATT BUS 2, and BATT 2 charging
During normal operations TRU ESS supplies power to what?
DC ESS BUS 3
When are batteries being charged?
Whenever the TRUs are powered from any source
TRU transforms AC to DC, is there a way to change DC to AC?
Yes, the inverter
BATT 1 or 2 normally charges through which TRU?
the associated side
Cant eh APU fully replace a failed IDG?
Yes
The APU GEN button, when depressed, does what?
- Connects the APU GEN to the AC bus tie according to source priority and provided the power is within limits
- Allows automatic operation of the electrical system
What happens when he APU GEN pushbutton is out?
- Opens the APU GEN cofactor and isolates the APU from the AC BUS TIE. The APU GEN is tripped off line and de-excited
- White stripe illuminates
During ground operations with the APU operating, the failure of an IDG will cause its respective AC BUS to get power from where?
APU GEN
You receive the aircraft at the gate and it is powered by the AC GPU. You start the APU. Once it’s up and running how can you tell the APU GEN has automatically taken over the electrical load?
AVAIL light on the AC GPU button and the MFD electrical page shows green APU icon
In flight, with the APU operating, an intentionally disconnected IDG will cause the respective AC BUS to seek power from?
APU GEN
What happens when the GPU pushbutton is out?
Isolates the AC GPU from the AC BUS TIE
At the gate, ground power is connected. What do you have to have to get an AVAIL light outside and in the cockpit?
Volts/Amps/Freqs are within limits
How is it known that an AC GPU is plugged in and the outside GPU panel button displays IN USE?
- GPU buttons display AVAIL and the GPU icon is presented on the electrical synoptic page
- Once the GPU button is pushed in, the button will display IN USE. Connects the AC GPU to the AC BUS TIE according to source priority