Electrical Flashcards
What is an IDG? How many are on the E175?
Integrated Drive Generator, 2
What is the IDG output?
115VAC, 400Hz, 40KVA
What is the APU output?
115VAC, 400Hz, 40KVA
What does the GPU stand for? What is the GPU output?
Ground Power Unit, 115VAC, 400Hz, 40KVA
What is the RAT? What is the RAT output?
Ram Air Turbine, 115VAC, 400Hz, 15KVA
How many inverters are on the E175? How many VAC is the inverter?
1, 250VAC
What is the purpose of an inverter?
Converts VDC to VAC
When can the IDG power both AC buses?
On the ground and in flight
When can the APU power both AC buses?
On the ground and in flight up to FL330
Can the GPU power both AC buses?
Yes
What is the primary source of AC power?
IDGs
What happens when the IDG knob is in the AUTO position?
system logic controls contactor
What happens when the IDG selector knob is turned OFF?
opens contactor to break the circuit disconnecting the IDG from the electrical network
What happens when the IDG DISC position is selected?
This position mechanically disconnects the CSD (Constant Speed Drive) from the IDG
Can the flight crew reconnect the IDG after IDG DISC?
No, only maintenance can reconnect the IDG
Amber light accompanied by the EICAS oil message indicates
IDG disconnect is required due to High Oil Temperature or Low Oil Pressure
What are the secondary sources of AC power?
The APU, the GPU
What power source is required to start the APU?
DC Power is required
Either BATT 1 and BATT 2 or BATT 1 and DC GPU are required for APU start
What is the function of BATT 1 and BATT 2 for APU start?
BATT 1 controls the APU’s FADEC; BATT 2 is isolated from the network to exclusively power the APU START BUS
What is the minimum VDC for APU start?
22 VDC minimum must be noted during the Safety and Power On Checklist to consider APU start
What is the minimum VDC required to close the battery contactor during APU start?
18 VDC minimum required to close the battery contactor (connect the APU to the electrical network)
What is the minimum BATT 2 temperature required for APU start?
-20 degrees Celsius
What 3 methods/locations that can be used to turn on the GPU?
- AC GPU panel (powers AC&DC ground service buses and TRU1)
- Opposite the FWD lav (powers AC&DC ground service buses and TRU1)
- Cockpit overhead panel (powers whole aircraft network)
What are the messages/annunciations you will see if the parking brake is released with the GPU connected?
CAS message: GPU CONNECTED; Master Caution and aural warning
What CAS message will you see if the GPU is connected and power meets system requirements?
AVAIL
What CAS message will you see if the GPU is running and is the priority (powering the AC system)?
IN USE
What is the normal AC electrical priority?
- Onside (IDG)
- Inside (APU)
- Outside (GPU)
- Cross-Side (Other IDG)
What does the inverter power?
The inverter powers the AC STANDBY BUS when the normal AC power source is not available so that “A” igniters always have a source of power
What is the purpose of the RAT?
Emergency AC power source
Are there any altitude or airspeed restrictions for RAT deployment?
No
When does the RAT deploy and what does the RAT power?
The RAT automatically deploys if both AC buses lose power during flight (electrical emergency) to supply the ESS buses
Can the RAT be deployed manually?
Yes via the RAT Manual Deploy Lever
During RAT deployment, what source provides aircraft power?
The batteries provide power for approximately 8 seconds
What minimum airspeed is required for RAT operation?
130kts
What happens if the aircraft speed is below the minimum required (130kts) while the RAT is deployed?
The RAT will only provide power to the AC ESS bus; the BATTS will provide power to DC ESS bus and AC STANDBY bus; As airspeed decreases, load shedding occurs until AC ESS bus is no-longer powered
What sources provide the aircraft’s DC power?
3 TRUs, 2 Batteries, 1 DC GPU
What is a TRU?
Transformer Rectifier Unit, Converts AC to DC and can change the voltage
What is the output of the TRUs?
28 VDC, 300 A
What is the output of the batteries?
24 VDC, 27 AH
What is the output of the DC GPU?
28 VDC
What is the primary source of DC power?
TRUs
The TRUs convert ___ to ___
115 VAC to 28 VDC
Do the TRUs work together?
No, the TRUs work in isolation from each other
What is the secondary source of DC power?
The batteries
What type of batteries do we have?
NiCad (Nickel-Cadmium as electrodes)
How are the batteries charged?
Via any power source through the TRUs
What is the volt minimum to close the battery contactor?
18 Volts
How long will the batteries provide power during an electrical emergency?
10 minutes
What does the DC GPU connect to?
the APU start bus and replaces BATT 2 during APU start
How can the DC GPU be turned on?
By the button on the ramp
Can the DC GPU charge BATT 2?
No
What is SPDA an abbreviation for?
Secondary Power Distribution Assemblies
What is the purpose of the SPDAs?
manage electrical load, distribute power according to system logic, performs BITs on many items
What powers the SPDAs?
SPDAs receive power from the ICCs
In general, how to the ICCs and SPDAs work together?
The ICCs collect and confirm the power is safe and then sends it to the SPDAs, which distributes it
What is a hot bus?
A hot bus is a bus that is still powered ON when everything else is off - what is still powered ON when you get to the airplane in the morning cold and dark
What 8 items are powered by the DC HOT BUS 1?
Battery 1
FWD Service/Courtesy Lights
DC Ceiling Lights
Engine 1 Oil Level Indication
Engine 1 Fuel SOV
Engine 1 HYD SYS 1 SOV
Fire Bottle 1A (Handle 1, Bottle A)
Fire Bottle 2A (Handle 2, Bottle A)
What 9 items are powered by the DC HOT BUS 2?
Battery 2
CMC Central Maintenance Computer
Refuel/Defuel Panel
Engine 2 Oil Level Indication
Engine 2 Fuel SOV
Engine 2 HYD SYS 1 SOV
Fire Bottle 1B (Handle 1, Bottle B)
Fire Bottle 2B (Handle 2, Bottle B)
Water and Waste System Controller
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?
Bus ties automatically connect to provide no system degradation
What components power the AC system?
2 IDGs, APU, Inverter, RAT, AC GPU receptacle
What components power the DC system?
2 NiCad batteries, 3 TRUs, DC GPU receptacle
How does the IDG maintain a stable power output?
A CSD Constant Speed Drive attaches the IDG to the AGB Accessory Gear Box
What monitors and controls the IDGs?
Each has a GCU Generator Control Unit
Can 1 IDG power 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, only maintenance can reset the IDG
What is the primary purpose of the AC generators?
- To power the AC BUSES and AC ESS BUS which… 2. Power the 3 TRUs 1, 2, and ESS
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?
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 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 before the next GPU connection
What is the purpose of the DC GPU receptacle?
For APU start when batteries < 22 VDC; or If battery temp is < -20 degrees C
What is the minimum battery temperature for APU start?
-20 degrees C
What is the minimum battery voltage to close the battery bus-tie?
18 votls
What battery is used for the APU start?
BATT 1 powers the FADEC and EICAS for monitoring; BATT 2 powers the APU Start Bus
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
What powers the RAT?
Airflow turns the RAT propeller which spins the turbine inside
When will the RAT deploy?
Automatically deploys if AC BUSES are not powered; Manually by pilot
How long after deployment before the RAT will provide power?
8 seconds
Is there a total loss of power during the 8 second RAT deployment?
No. Batteries supply power to the DC ESS BUSES and AC STANDBY BUS
What does the RAT power?
AC ESS BUS
AC STBY BUS
DC ESS BUSES 1,2,3
HOT BATT BUSES 1,2
Batteries
What is the minimum airspeed for the RAT?
130 KIAS; Load shedding occurs below this speed
When is the RAT icon displayed on the electrical synoptic page?
When the RAT is deployed
What manages the electrical system?
4 ICCs, 2 SPDAs
What is an ICC?
An electrical control device, which provides power distribution and protection for electrical loads
What is an SPDA?
An electrical load-management unit (powered by the ICCs), that distributes electrical loads to aircraft systems according to distribution logic and performs BITs on many components
Can the flight crew reset the ICC and SPDA remote electronic CBs?
ICC CBs can only be reset by maintenance; SPDA CBs can be reset via the MCDU
What is a MAU or modular avionics unit?
Cabinet of avionics components and some non-avionics components. MAU 1 and 2 are in the FWD Ebay. MAU 3 is in the mid ebay
What does the AVAIL lamp on the overhead panel mean?
The external power is connected and all quality requirements are satisfied.
If the APU is available and one engine generator fails, the failed generator is replaced by?
The APU generator
Can you reconnect the IDG in flight?
No
The STBY AC BUS is normally powered by the ESS AC BUS. It will be powered by the inverter when
the aircraft is powered by batteries only
What converts DC to AC?
The inverter
What does IDG stand for?
Integrated Drive Generator, attached to the AGB
What is difference between the electrical power created by the engines v the APU?
The engines have a CSD Constant Speed Drive that converts variable engine speed into constant generator speed
How is the IDG oil system cooled?
Air Cooled
What controls the IDGs?
The GCUs Generator Control Units
What could happen if the IDG disc light illumiunates but you don’t disc the IDG?
The IDG features an input shaft shear section and a thermal disconnect operation that will permanently disconnect the IDG if there is no manual disconnection.
How does the RAT maintain a constant electrical output?
The RAT blades are variable-pitch type
How will you know if the RAT failed to deploy and must be deployed using the RAT manual deploy lever?
The BATT DISCHARGING EICAS message appears.
What is the purpose of the inverter?
To provide backup electrical power while the aircraft is only powered by the batteries (during RAT deployment).
What is the only item on the aircraft to provide single phase power?
The inverter converts 28VDC to 115VAC, 400Hz, single-phase
What are the 4 ICCs?
The Left Integrated Control Center LICC, Right Integrated Control Center RICC, Emergency Integrated Control Center EICC, and Auxillary Integrated Control Center AICC (for APU start)
What is the secondary DC power source?
2 Nickel-Cadmium Batteries
Where are batteries 1 and 2 located?
BATT 1 in the Fwd E-bay, BATT 2 in the aft E-Bay
What charges the batteries normally?
Any AC power source, Even the RAT
With BATT 1 OFF, or BATT 2 OFF, will the batteries be connected to anything?
Yes, the HOT BATT Buses
What does an ICC provide? What is it physically?
Power distribution and protection. It is an electronic device.
Where are the respective ICCs located?
LICC and RICC in the middle e-bay, EICC in the fwd e-bay, and AICC in the aft E-bay (for APU start)
What are the components of the ICC electrical device?
AC/DC buses
Thermal Circuit Breakers (remote via the MCDU)
LRUs Line Replaceable Units
LICC: AC Bus 1, DC Bus 1, AC/DC Ground Service Buses, LRUs: TRU 1, GCU 1, External Power Modules, Several Thermal CBs
RICC: AC Bus 2, DC Bus 2, DC ESS Bus 2, LRUs: TRU 2, GCU2, ACGU (Aux GCU), several thermal CBs
The DC ESS Bus 2 is here instead of the EICC in case of damage to the fwd e-bay
EICC: AC ESS Bus, DC ESS 1/3, Standby AC Bus, HOT BATT Bus 1 ,LRUs: TRU ESS, several thermal CBs
AICC: APU start bus, HOT BATT BUS 2, several thermal CBs
How will you know if a remote CB trips in the ICC? Can they be reset in the air?
REMOTE CB TRIP EICAS Message
They cannot be reset in-flight
What is the SPDA purpose? What does SPDA stand for?
SECONDARY Power Distribution Assembly. Manages and distributes power from the ICCs based on the AUTO logic
Where are the SPDAs installed?
SPDA 1 in the fwd e-bay, SPDA 2 in the mid e-bay
Each SPDA has slots and electronic remote CBs, unlike the ICCs which are thermal CBs. If a SPDA CB trips, can it be reset?
Yes via the MCDU because it is electric, unlike the ICCs which are thermal and can only be reset on the ground. Vital system CBs are on the circuit breaker panel in the cockpit.
What normally powers the AC ESS bus?
IDG 2
What do TRUs do?
“Rectify” AC power to DC, and “transform” it down in voltage
Where are the GCUs located and what do they do?
They are Generator Control Units that control the IDGs. They are located in the RICC and LICC as LRUs. They send the signal to open or close the IDG line contactors, which are also located in the LICC and RICC.
Can DC ground power be used in lieu of AC ground power?
No. DC ground power (GPU) can only be used for APU start.
Can the AC or DC GPUs be powered on from outside the airplane?
Yes via the respective buttons which will power the ground service buses OR via the FA panel GND SVC button. NOTE: THE DC GPU can ONLY be powered on from outside the airplane via the button
BIT
Built-In Test
BTC
Bus Tie Contactor
GCU
Generator Control Unit
IDG
Integrated Drive Generator
MAU
Modular Avionics Unit
PBIT
Power Up Built-In Test
When will the BATT 1(2) OVERTEMP EICAS warning be triggered?
Whenever the battery temperature reaches 70°C for at least 2 seconds, the associated indication becomes red and the EICAS WARNING message BATT 1 (2) OVERTEMP is triggered.
