Electrical System 2 (DC Power System) Flashcards
What is the purpose of a transformer rectifier unit (TRU)?
To transform AC power to DC power
Where does the right TRU receive power from?
From the right generator and the AC bus contactor
same for left with the left generator
Is one generator capable of supplying power to both TRUs in the event of a generator failure?
Yes, due to the crossover relay
If one TRU fails, will the other TRU produce enough DC power to carry the entire electrical load?
Yes
When either TRU falls below what voltages does a RECTIFIER FAILURE PFL and an AVIONICS advisory generate?
25.5 V for 2 seconds
How many amps do the TRUs operate at?
50 Amps
What is the voltage of the battery?
24 V lead acid battery
The TRUs convert the AC power from the generator to what voltage of DC power?
28 V DC
Why is there no interruption of power to the DC system if one TRU fails?
Due to the Diode Module. The Diode Module parallels the power output from both TRUs into a single output, so the DC busses are connected to the TRUs via a single diode, providing no interruption of power.
How many DC Buses are there and what are they?
- Left Essential DC bus
- Right Essential DC bus
- Nonessential DC bus
- Battery Bus
During normal operation with both generators online, what buses are active and powered by the TRU?
The two essential DC buses and the nonessential DC bus
What buses does the battery provide DC power to?
The two essential buses and the battery bus
In the event of a dual TRU failure or double gen failure, how long will the battery power the two essential DC busese?
For approximately 15 minutes at 80% charge
What is the minimum voltage required of the battery to connect to the essential DC buses?
18 V
How low of a voltage can the battery be at in order to accept a charge?
10 Volts
When the battery relay closes (i.e. connects the battery to the essential DC buses), until what voltage will it stay closed?
10 Volts
What component deenergizes and disconnects the nonessential bus?
The bus contactor
What voltage change causes the bus contactor to drop the non essential DC bus offline?
A voltage change from 28 V to 24 V
If the bus contactor is triggered, what is illuminated?
- MASTER CAUTION light
- XMFR RECT OUT light
- CAUTION, CAUTION voice message 1.5 seconds after the Master Caut light
Until what voltage does the battery supply DC power to the essential busses?
Until 10 V
A single TRU failure generates what warning tones and signals?
A PFL fault and an AVIONICS alert on the HUD/MFD
What are the only three times that battery power is required?
- During starts when the APU is not used
- When both TRUs fail
- When both generators are inop or drop off-line
