Electric Flashcards
HMG
5 Kva
115 V, 400 Hz, 3-phase AC
Purpose = Provide an AC power source to the AUX TRU when/if the Engine and APU GENs are unavailable.
Located in the Aft Equipment compartment
Batts and Chargers
(2) Batts:
24 V, 24 cell
45 Amp Hr
Lead acid
(2) Chargers:
38 amp CRG mode
40 amp TR mode
Note: Batts will power the L and R ESS DC buses for ~30 min if (2) APU starts have been attempted, with ea attempt not lasting longer than (30) sec
Generators
(3) 40 kva, 115 V, 3 phase AC
IDG’s = Constant speed 12,000 RPM, Oil cooled
Load Limit = When ambient > 110F/43.5C, limit IDG load to 45% (18Kva) to keep fuel temp < 95C
E Batts
(4) L/R Avionics & Fwd/Aft Lights
24 V
9 Amp Hr
Lead acid
What do the Avionics E-Batts power?
(Via the L & R ESS DC Buses)
Left:
1. Combined WOW
2. MCDU #3
3. VHF Comm #1
4. IRU #1
5. Pilot Audio Panel
6. Clocks
7. SFD, EBDI
Right:
1. Landing Gear Indication
2. Landing Gear Control
3. Fuel Qty
4. MCDU #1
5. ATC #1
6. IRU #2
7. IRU #3
What does the HMG power?
L STBY AC BUS:
#1 TAT Heat
L E-Batt Charger
L Pitot Heat (-> ADM 1)
R STBY AC BUS:
#2 TAT Heat
R E-Batt Charger
STAB SEC AC (Flap/Stab Pwr?)
AUX TRU - powers the L and R ESS DC BUS’s:
Flight Instruments
Nav and Comm Radios
STBY Inverter (powered by the ESS DC BUS’s) will provide single-phase AC Power to the ESS AC BUS:
Cabin Pressure Ch 1
Right Pitot Heat (-> ADM 2)
STBY Pitot Heat (-> ADM 3 & SFD)
How many buses are powered by the HMG?
(5)
L STBY AC
R STBY AC
L ESS DC
R ESS DC
ESS AC phase A (via E-Inv via L or R ESS DC bus)
Probes powered during HMG ops?
1 AOA Heat - ESS DC Bus
#2 AOA Heat - ESS DC Bus
#1 TAT Heat - L STBY AC Bus
#2 TAT Heat - R STBY AC Bus
L PITOT Heat - L STBY AC Bus
R PITOT Heat - ESS AC Bus
STBY PITOT Heat - ESS AC Bus
Ground Service Bus:
Power Source Priority
- R MAIN DC BUS
- External DC
- R MAIN BATT
GSB: Powered Items
Fueling panel
Engine oil
Wheel well lights
Beacon light
Utility lights
NBPT
No Break Power Transfer
Controlled by L/R BPCUs - matches/parallels the phases of the IDGs and/or APU Gen
All auto power transfers will be NBPTs except those b/w an external AC Power source and APU Gen (not an IDG)
Break Power Transfer occurs when?
Generator failure
Engine failure
Fire Handle pulled
Causes E-Batts to activate
How are the GCU’s powered?
Initially via the L and R ESS DC buses, then via the permanent magnet generator (converts AC to 28V DC)
BPCU’s
Bus Power Control Units (2). Power distribution and protection - receive AC power –> AC buses.
L (LEER) monitors L MAIN AC Bus + External AC
R (REER) monitors R MAIN AC Bus, ESS AC Bus, and External DC
AC Power Distribution Buses
L MAIN AC (L Power Distribution Box)
R MAIN AC (R Power Distribution Box)
ESS AC (L Power Distribution Box)
L STBY AC (floor next to AUX TRU)
R STBY AC (floor next to AUX TRU)
60 Hz AC (Baggage compartment)
IDG Limitation
IDG load limited to 45% (18 kVA) when ambient temp > 110°F
In order to maintain steady state fuel temps below 95°C
HMG Limitation
Move speed brake slowly - 3 sec for full deployment
How many DC Buses are there?
(4) Main:
1. L MAIN
2. R MAIN
3. L ESS
4. R ESS
- L EMER
- R EMER
- FLIGHT INSTRUM
External AC power is capable of powering what buses?
All buses. The main batts may also be charged.
How many GSB switches are there, and where are they located?
(3)
Fwd external switch panel
Tail compartment electrical power ctrl panel
Flight deck fuel grnd service ctrl panel
When will the MAIN BATTERY switches on the overhead panel illuminate ON?
- When powering the ESS DC Buses
- Starting the APU
- AUX Hyd pump is operating
When Emer Power Sys is armed, when will the E BATTs activate?
Any time either L or R ESS DC Bus power drops below 20 V
What is the normal AC power source for the AUX TRU and ESS AC bus?
L MAIN AC bus
If the L MAIN AC bus is unpowered, will the AUX TRU and ESS AC bus auto switch to another power source?
Yes. Both switch to the R MAIN AC bus
What is the “DEAD BUS” power logic for the AUX TRU?
ESS before MAIN
LEFT before RIGHT
What is the purpose of the E-Inverter?
To power the ESS AC bus phase A items (if the ESS AC bus loses power)
What is the normal position of the E INV switch?
Auto
How long do you wait b/w selections of L ESS and R ESS when using HMG?
10 sec
The 60Hz converter can be used to..
Convert aircraft 400Hz power to household power for the outlets in the galley and pax cabin
If you lose L MAIN AC BUS power, what happens automatically?
- AUX TRU transfers to R MAIN AC BUS and powers L ESS DC BUS
- ESS AC bus transfers to R MAIN AC BUS
What 2 sources can power ESS DC buses simultaneously?
L / R MAIN Batts
AUX TRU (when powered by the HMG)
The MAIN BATT switches illuminate ON when the MAIN BATTS are…
- Powering the ESS buses (batts are being used)
- Starting the APU
- AUX pump is operating
Describe a Break Power Transfer
A momentary interruption of power when switching AC power sources. Can occur when a source of AC power fails or an IDG is not involved in the power transfer
What is the function of BUS TIE ISLN SWITCH?
Isolates the Main AC Bus from all AC power sources except the onside IDG
If the R Main TRU is selected, what is the power source for the R Main TRU?
L MAIN AC Bus
What is the color of the GEN switch if the generator is turned off?
Black/Gray
What appears in the GEN switch if the GEN FAILED?
Amber OFF
On the ground, the ground service bus may be powered by?
- R MAIN DC Bus (preferred)
- R MAIN BATT
- Ext DC Power cart
How can you tell when the GND SVC BUS is powered by the right main batt?
Beacon light on
Is GND SVC BUS powered in flight? And by what?
Yes. R MAIN DC Bus
How do you know the generator has failed if looking at the synoptic?
GEN outline is Amber color
Will GND SVC BUS turn off auto?
Yes, when:
Main cabin door is closed
Fwd external switch panel access door is closed
Tail compartment door closed
Note: All doors must be closed for auto shutoff
What appears on MCDU 1 & 3 with E Batts?
1 - STBY ENG INST and FUEL
3 - BACK UP RADIOS, VHF COM1/NAV1, and ATC 1 (Transponder)
What is the power source of the left and right main batt chargers?
L and R MAIN AC Buses
When the aircraft operates on emergency batts the crew can only tune:
COM 1 / NAV 1 / ATC 1 on MCDU 3
If you remove AC external power, with it auto switch to DC external power?
No, need to deselect EXT PWR switch and RESELECT for DC ext pwr
Why do you use DC EXT?
Start APU with Low Batt Voltage
