Electrical Flashcards
List the AC Power Components
List the AC Power Components
- (2) IDGs (primary) 115 VAC, 400 Hz, 40 KVA, three phase
- (1) APU115 VAC, 400 Hz, 40 KVA, three phase
- (1) AC GPU Receptacle 115 VAC, 400 Hz, 40 KVA, three phase
- (1) RAT - 115 VAC, 400 Hz, 15 KVA, three phase
- (1) Inverter 250 VDC to 115 VAC direct to AC STBY BUS, one phase
List AC Power Priority
List AC Power Priority
- Onside (IDG)
- Inside (APU)
- Outside (AC GPU)
- X-Side (Other IDG)
What components power the DC system?
What components power the DC system?
3 TRUs (Transformer Rectifier Units) – 28VDC, 300A
2 Batteries – 22.8VDC, 27AH
1 DC GPU – 28VDC
TRUs (Transformer Rectifier Units)
TRUs (Transformer Rectifier Units)
Primary DC power source
Converts 115VAC into 28VDC
Each works in isolation from the other
Batteries
Secondary DC power source
2 NiCad batteries
Back-up for DC ESS
Charged via any AC power source thru the TRUs
18.0 volts minimum required to close the battery contactor
Will provide 10 minutes of power during an electrical emergency
DC GPU
Hooks directly to the APU start bus and replaces BATT 2 during APU start.
Can only be turned on by a ground ramp button
Cannot charge BATT 2
How many networks make up the electrical system on the airplane? Why?
n
How many networks make up the electrical system on the airplane? Why?
2 independent networks
Redundancy and fault isolation
What happens if a power generating source fails?
What happens if a power generating source fails?
Bus ties automatically connect to provide no system degradation.
IDG in off means?
IDG in off means?
IDG is isolated from the respected AC bus but not off
IDG in disc means?
IDG in disc means?
IDG is mechanically disconnected from the CSD
What happens if IDG stays on after disc light comes on?
It will shear if it is too much torque or melt if too hot.
How does the IDG maintain a stable power output?
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?
What monitors and controls the IDG’s?
Each has a Generator Control Unit (GCU)
Can one IDG supply the entire electrical system?
Can one IDG supply the entire electrical system?
Yes
What will cause the amber IDG light on the overhead panel to illuminate?
What will cause the amber IDG light on the overhead panel to illuminate?
High oil temperature 335F
Low oil pressure 140PSI
Can the GPU power both buses?
Can the GPU power both buses?
Yes
What does the DISC position on the IDG do?
What does the DISC position on the IDG do?
Disconnects IDG from CSD. If this fails it mechanically shears off
the CSD from the IDG
If an IDG is manually disconnected can it be reconnected by the flight
crew?
If an IDG is manually disconnected can it be reconnected by the flight
crew?
No. This is a maintenance function
When do you know you need to DISC the IDG?
When do you know you need to DISC the IDG?
LOW Oil pressure low 140psi
HOT Oil temp high 335F
Amber light is on
disconnect switch hold for one second but no more than 3 secs
Flight crew can reconnect IDG after DISC has been engaged?
Flight crew can reconnect IDG after DISC has been engaged?
No, that is a MX function on the ground
What is the primary purpose of the AC generators?
What is the primary purpose of the AC generators?
To power the AC BUSES 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?
What is the purpose of the Transformer Rectifier Units?
To convert 115 VAC to 28 VDC
Can the APU replace a failed IDG?
Can the APU replace a failed IDG?
Yes
How is it known that an AC GPU is hooked up to the airplane and ready to provide electricity?
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
Once the GPU button is pushed in, the button will display IN USE provided another AC power source is not available.
What does it mean if the AC GPU is plugged in and the outside GPU panel button displays IN USE?
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?
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 conn
What (2) combinations provide power to accomplish APU
START?
What (2) combinations provide power to accomplish APU
START?
1. BATTs 1 & 2
2. BATTs 1 and DC GPU
Which Battery controls the APU’s FADEC?
Which Battery controls the APU’s FADEC?
BATT 1
Which battery is isolated from the network during APU
START to exclusively power the APU START BUS?
Which battery is isolated from the network during APU
START to exclusively power the APU START BUS?
BATT 2
What is the minimum VDC required during the Safety &
Power On Checklist to consider APU Start?
What is the minimum VDC required during the Safety &
Power On Checklist to consider APU Start?
22 VDC
What is the minimum battery voltage required to close the battery
contactor?
What is the minimum battery voltage required to close the battery
contactor?
18 VDC
What is the min BATT 2 temp for APU start?
What is the min BATT 2 temp for APU start?
-20 C
The APU is a primary AC source (T/F)
The APU is a primary AC source (T/F)
False
What is the purpose of the DC GPU receptacle?
What is the purpose of the DC GPU receptacle?
For APU start when batteries < 22.0 VDC, or
If battery temp is < -20°C
How many ways can the AC GPU be turned on?
How many ways can the AC GPU be turned on?
- AC GPU panel (AC/DC GS Panels & TRU 1)
- (1) Opp. FWD Lav (AC/DC GS Panels & TRU 1)
- (1) Switch Cockpit Overhead Panel (Powers whole aircraft network)