Study Guide Electrical Flashcards
How many networks make up the electrical system on the airplane? Why?
- 2 Independant networks
- Redundancy and fault isolation
What Happens is a power generating source fails?
- Bus ties automatically connect to provide no system degradation.
What components power the AC system?
- 2 Integrated Drive Generators (IDG)
- Auxiliary Power Unit (APU)
- Inverter
- Ram Air Turbine (RAT)
- AC GPU receptacle
What components power the DC system?
- 2 NiCad batteries
- 3 Transformer Rectifier Units (TRU)
- DC GPU receptacle
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 IDG’s?
Each has a Generator Control Unit (GCU)
Can one IDG supply the entire electrical system?
Yes
What will cause the amber IDG light on the overhead panel to illuminate?
- High oil temperature
- Low oil pressure
If an IDG is manually disconnected, can it be reconnected by the flight crew?
No. This is a maintenance function.
What is the primary purpose of the AC generators?
- To power the AC BUSSES and AC ESS BUS which…..
- Power the 3 Transformer Rectifier Units (TRU) 1,2, and ESS
What is the purpose of the Transformer Rectifier Units?
To convert 115 AC to 28 VDC
Can the APU replace a failed IDG?
Yes
What is the AC electrical system’s priority?
- On Side (IDG)
- Inside (APU)
- Outside (GPU)
- Cross-Side (other IDG)
How is it known that an AC GPU is hooked up to the airplane and ready to provide electricity?
GPU button displays [AVAIL] and the GPU icon is presented on the electrical synoptic page.
What does it mean if the AC GPU is plugged in and the outside GPU panel button displays [IN USE]?
- Ground Service Bus is in use
- Cockpit GPU button will display [AVAIL] even though the ground service bus is in use
If the airplane is using the AC GPU and the APU is started, what should the pilot be sure to do?
Deselect the GPU button before the next GPU connection.
What will charge the batteries?
Any AC power source.
How long will the aircraft’s batteries last with no recharging?
10 minutes
What is the purpose of the DC GPU receptacle?
- For APU start when the batteries are < 22.5 VDC or
- If battery temp is < -20 C
What is the minimum battery temp for APU start?
-20 C
What is the minimum battery voltage to close the battery bus-ties?
18 volts
What battery is used for the APU start?
- BATT 2 powers the APU start bus
- BATT 1 powers the FADEC & EICAS for monitoring
What is the purpose of the Inverter?
Converts 28 VDC from the batteries to 115 VAC to power the AC STANDBY BUS when an AC source is not available
What is on the AC STANDBY BUS?
Engine exciters 1A and 2A
