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
