Electrical Flashcards
What type of power to most of our generators produce
AC
What type of power does the aircraft use
115VAC and 28VDC electrical power
What’s our primary source of electrical power
- AC electrical power
- supplied by 2 engine driven integrated drive generators
What’s a transformer rectifier unit (TRU) do?
Converts 115VAC to 28VDC power
What does the AC power center (ACPC) do?
Distributes power to all AC buses during normal operations
What’s an IDG?
It’s an “integrated drive generator. It consists of a constant speed drive and a generator. It’s the aircrafts primary source of AC power.
What are our alternate electrical sources
The Auxiliary Power unit (APU) and Air Driven Generator (ADG)
GCU fault protection
- Over/under voltage
- over under frequency
- generator phase sequence…
Electricity generation altitude limitations
Engine IDG’s = 41,000
APU. = 41,000
ADG…
Integrated drive generators
- Consists of a generator and a constant speed drive
- Constant speed drive takes variable N2 and produces a constant 12,000RPM generator speed. This creates a consistent electrical output.
When will the IDG FAULT switch light illuminate?
The IDG FAULT switch light illuminates on the overhead panel when there’s either high IDG oil temperature or low IDG oil pressure.
QRH checklist types
Command, response type
What’s the correct response to a request to confirm something with the other pilot?
Either “I agree” or “no’”
What happens when you hit the IDG fault switch on the overhead panel
The disconnect solenoid moves, which allows the disconnect plunger to engage the IDG worm shaft and disconnects the IDG by spreading the jaw tooth clutch.
IDG critical temperatures
At 168ºC IDG oil temp, the fault light will come on
At 186ºC the hot IDG oil will melt the disconnect solenoid sauter point and disconnected the IDG automatically
What are the different AC buses?
Bus1
Bus2
Ess bus
Serv Bus
AC BUS 1 power priority
- 1st from IDG 1
- 2nd priority is to get electricity from APU generator
- 3rd priority is IDG 2
- 4th priority is external ground power
What’s the ground power priority?
Lowest power priority. You have to turn off APU and engine to get ground power to work.
AC BUS 2 power priority
1st is IDG 2
2nd is APU generator
3rd is IDG 1
4th is External power
AC Essential bus power and faults
- Gets is power from AC BUS 1, and therefore its generally powered by IDG 1.
- If the AC BUS 1 loses power, AC BUS 2 will automatically power the AC ESS BUS
- The AC ESS XFR switch light illuminates any time the AC BUS 1 has failed and is being powered by AC BUS 2. If it doesn’t automatically switch to being powered by by AC BUS 2, pressing the switch light will manually switch to AC BUS 2
AUTO XFER inhibit switch light
- FAIL: illuminates when a bus fault or generator overcurrent is detected by the GCU. The affected generator is taken offline. The GCU automatically inhibits the auto transfer system on the affected side.
- Pressing the switch light turns off the Bus 1/2 respectively. Hitting it again turns the bus back on.
AC external power switch light
- AVAIL means the ground power is connected and is the correct voltage, frequency, and phase
- IN USE means that the aircraft systems are being actually power by ground power
Ground power control panel and plug in location
… I’ll get back to it…
AC external service switch
-Looks like the internal switch light. Pressing the external switchlight only powers the SERV bus.
Air driven generator
-Automatically deploys when AC Bus 1 and bus 2 to fail simultaneously.
-Can
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ADG powers which things
- AC essential bus
- Slats and flaps (operated at half speed)
- Stab trim channel 2
- Hydraulic 3B
Will hydraulic 3B run in the off position when the ADG is running?
Yes. When the ADG is running, the ADG
What happens if the ADG is running and youre able to restablish alternate power.
The essential bus will remain powered by the ADG until you push the “PWR TXFR OVERRIDE” and then the AC1/2 will power the essential bus
ADG speed
- Between 155-160kias start load shedding with the essential DC bus
- Need to configure for landing no slower than 140kias
What are our DC power sources?
4 Transformer rectifier units (TRU’s) and 2 batteries (main battery and APU battery)
What charges the batteries?
Main battery is powered by AC Bus1
APU battery is charged by the AC service bus
Battery charging is controlled automatically
How many TRU’s do we have and where are they located?
4, all in the nose compartment.
How many DC buses do we have?
9
What are the DC buses?
DC Bus1 DC Bus2 DC SERV bus DC UTIL bus DC ESS bus DC BATT bus DC APU BATT DIR bus DC MAIN BATT DIR bus DC EMER bus (not normally shown)
What is the max TRU load
-All 4 are rated at 120AMPS
What are the 4 TRU’s
TRU1, TRU2, ESS TRU1, and ESS TRU2
How many DC Tie contactors are there? What are there names?
5 DC tie contactors exist
- MAIN TIE
- CROSS TIE
- ESS TIE
- DC ESS TRU 2 transfer contactor
- Service BUS contactor
Can we control the TIE’s?
Negative. It’s all automatic.
What closes and opens the ties?
The DCPC’s (DC power center’s)
What is the most common DC bus to lose when a TRU fails?
The UTIL bus
What does the battery master switch do?
Allows the batteries to power the DC BATTERY BUS via both APU BATT DIR BUS and MAIN BATT DIR BUS
Which busses are hot
- APU BATT DIR BUS
- MAIN BATT DIR BUS
- DC EMER BUS
Max permissible time for ground operations with battery power only
5 minutes, the fans that cool the EICAS CRT screens are AC powered so without turning on the APU, engines, or applying ground power, the EICAS screens could overheat