Electrical Flashcards
What supplies power to the DC system?
Four engine driven generators
(28 VDC, 400amps)
1 APU starter generator
(28 VDC, 400amps)
Two NiCad batteries
(24VDC, 44AH)
One lead acid backup battery
(24VDC, 5AH)
Available for ground servicing: one GPU
(28VDC, 1,600amps)
Into how many networks is the electrical system divided during normal operations?
2
What provides system management, and protection for the electrical system?
Electronic distribution logic and generator control units
When a GPU is connected, can the APU be used for electrical power?
The GPU has priority over all other systems
Can a GPU be used to charge the batteries?
No
Which generator supplies the left electrical network?
1 and 3
To which generators is the APU normally connected in parallel
2 and 4
What is the voltage and amperage of the NiCad main batteries?
24V 44AH
To which bus are the generators connected to charge the number one battery during normal flight?
DC bus 1
Which battery provides electrical power for APU starting
No 2
When on the ground with the batteries as the only electrical power source which buses are deenergized
The Shed Buses
During APU starting, which battery is isolated from the load buses
No 1
For how long can the batteries be expected to provide power in an electrical emergency
40 minutes
What is the definition of an electrical emergency?
A loss of all generators
In an electrical emergency, to which buses only does the EDL automatically configure the system dedicated to the batteries
Essential and central
If the automatic transfer fails, how would you manually connect the batteries on the essential bus?
Press the essential power button on the electrical panel
How can all DC buses be energized with the aircraft on the ground?
At least three generators online
GPU on and powering the aircraft
One generator on and shed bus override selected
Which bus is energized by connecting the GPU to the airplane with batteries off
Ground service
At what battery temperature will a BATT OVTEMP warning message be shown on the EICAS
70°c
What is the voltage and amperage of the backup battery?
24v 5Amp
What is the purpose of the lead acid back up battery
It provides stabilized power for operation of the GCU protective function, even in case of a short circuit when system voltage may drop near 0 V
What conditions must be met for the back up battery to be charged?
The system must be energized through a power source, other than external power, and a battery selector must be set to the auto position
What is the primary power source for the aircraft?
4 28 VDC engine driven generators
At what N2 engine speed will the aircraft generators come online?
56%
At what amperage will the GEN 1 (2,3,4) OVLD caution message be generated
400 Amps
What is the purpose of the GCUs
They isolate the generators from the DC buses, if an overvoltage is detected
How many times can a generator be reset after a failure?
One time
The APU and GPU are connected to the aircraft electrical system, through which DC bus, which also provides loads sharing in the event of generator failure or engine shutdown
Central bus
When does the APU generator start supplying electrical power to the system?
At 95% plus 7 seconds
When the airplane is in the air, what is the minimum system requirement for all DC buses to be kept energized
Three generators online
Where can all generator currents and voltages be monitored?
The electrical page of the MFD
Which lights are powered by the ground service bus?
Cockpit dome, lights, courtesy/stair lights, galley lights, passenger cabin lights, lavatory lights, baggage/service compartment lights
What powers the AC system?
115 VAC, single phase static inverter
Why should the avionics master push buttons be pushed out while starting the APU?
They disconnect some navigation and communication equipment from the load buses to prevent possible damage from voltage surge
What is the maximum load on an engine generator?
400 amp
What is the maximum load on the APU starter generator up to 30,000 feet?
400 amp
What is the maximum load on the APU starter generator above 30,000 feet
300 amp
What is the minimum battery temperature for the APU start?
-20°C
What is the minimum battery voltage for APU start?
23.5 V
Below, what voltage must the battery be physically removed from the aircraft by maintenance for recharging
19 V
List the items on hot bus 1
Emergency locator transmitter, engine, 1/2 fire extinguisher bottle A, fuel pressure refueling, engine 1 fuel shut off valve, hydraulic shut off valve, engine 1
What does an illuminated stripe in a button on the overhead panel mean?
The switch is not in its normal position For Flight
