E175 Electric System Flashcards
How many networks make up the electrical system on the Airplane?
- 2 independent networks
- redundancy and fault isolation
What happens if a power-generating surface fails?
- bus ties automatically connect to provide no system degradation
What components power the AC system?
- 2 integrated drive generators IDG
- APU
- inverter
- the RAT
- AC GPU receptacle
What components power the DC system?
- 2 NiCad batteries
- 3 transformer rectifiers 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 GCU generator control unit
Can one IDG supply the entire electrical system?
Yes
What will cause the Amber IDG light on the O/H panel to illuminate?
- high oil temp
- low oil pressure
If an IDG is manually disconnected can the flight crew reconnect it?
No- it’s a maintenance thing
What is the primary purpose of the AC generators?
- To power the AC busses and the AC ess bus which….
- power the 3 transformer rectifier units TRU 1, 2 and ESS
What is the purpose of the transform rectifier units TRU?
To convert 115vac to 28DC
Can the APU replace a failed IDG?
Yes- up to 33,000 feet
What is the AC electrical systems priority?
- Onside IDG
- Inside APU
- Outside GPU
- Cross-Side (other IDG)
Note: the plane uses an onboard AC power source before an external AC source
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?
- 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
What will charge the batteries?
Any AC power source
How long will the planes batteries last with no recharging?
10 minutes
What is the purpose of the DC GPU receptacle?
- for APU start when batteries <20 VDC or,
- if battery temp is < -20c
What is the min battery temp for APU start
-20C
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
