Electrical Flashcards
If a breaker trips, what criteria should be used to determine whether or not to reset?
Reset once, only if the affected component is required for safe flight and landing (unless specifically directed by a QRH checklist procedure)
A NBPT can occur between the APU Gen and what other electrical component?
Engine IDG
How are BUS TIE isolation contactors controlled (RAXC / LAXC)?
By the isolation switches on the cockpit overhead panel, GCUs or BPCUs
What is indicated by an amber OFF light in either GEN switch?
the IDG has been isolated by the GCU or the BPCU
During normal operations (IDGs powering aircraft), the Ground Service Bus receives power from which bus?
Right Main DC Bus
When does the Emergency Power System activate automatically in the ARM position?
ESS DC bus voltage drops too low, or after a 2.5G impact
What buses are powered during HMG operation?
Both Standby AC Buses, Both ESS DC buses, ESS AC Bus
Where does the E inverter receive power from?
Left or Right ESS DC Bus
When is the AUX TRU capable of providing power to both the left and right ESS DC buses?
Standby Electrical Power (HMG)
Where do the battery chargers receive their power inputs from?
L and R MAIN AC buses
How many emergency batteries are installed on the airplane?
4
LEER, REER and AEER
How are the emergency batteries charged?
Left = Left standby AC bus
Right = Right standby AC bus
Forward lighting = Left main AC bus
Aft lighting = Right main AC bus
When do the E-Batts come on in armed position?
Less than 20V DC
Minimum battery voltage for APU start?
22 V
Below what voltage will main batteries need a maintenance deep cycle recharge?
7 V
What items are capable of being powered from the battery tie bus?
- Aux hydraulic pump
- APU Starter
- ESS DC Buses
Below 20 V, approximately how long with it take to fully recharge the batteries?
90 Minutes
What 3 items will illuminate the battery switch capsule lights?
- When the batteries are powering the ESS DC buses
- When the AUX HYD Pump is selected ON
- When starting the APU
Which battery is utilized to close the main door when using the outside door switch?
Right battery, which is wired directly to the main door electrical control circuit
What is the output rating of the HMG?
5 kVa = 100% on the synoptic indication
How is the HMG powered?
Left hydraulic system pressure, or via the PTU (Right pressure, with fluid in the Left hydraulic system)
HMG powers which buses?
L and R Standby AC Buses, AUX TRU (supplies power to the L and Right ESS DC buses) and the ESS AC Bus through the E Inverter
What item will be lost with only one AC power source in flight?
Galley power
How many TRUs are normally operating in flight?
5 = 2 Main, 2 ESS and 1 AUX
Which TRU is not dedicated to a single bus?
AUX TRU
If the right main TRU fails, what should automatically power the right main DC Bus?
AUX TRU
If a generator fails, will a BPT or a NBPT occur?
BPT
If a generator is selected off while running, will a BPT or a NBPT occur?
NBPT
If a running engine is shutdown with the fuel control switch, will a BPT or a NBPT power transfer occur?
NBPT
If an engine fails, will a BPT or a NBPT occur?
BPT
If the ground service bus is selected ON, what will power the bus if DC external power is connected to the aircraft?
DC external power
In flight, how is the ground service bus normally powered?
Right Main DC Bus
When the ground service bus is turned on, what light turns on?
Lower beacon
Which batteries are activated when the external battery switch is turned ON?
Both main batteries
What buses are powered with an external DC power cart connected to the aircraft?
- L and R ESS DC
- L and R Main DC
- GND SVC Bus
- ESS AC (via the E inverter)
What electrical components are located under the forward floor?
TRUs and E Inverter
What is the IDG load limit when operating at high ambient air temps?
45% (18 kVa) when greater than 43c in order to maintain steady state fuel temperatures below 95c
Speedbrake limitation in HMG operations
Speedbrakes may be used, provided operation is slow (3 seconds for full range of handle movement)
How is the left main TRU powered when the L MAIN TRU switch on the overhead panel is selected to “R AC”?
The L MAIN TRU receives power from the R MAIN AC bus
What is the indication associated with a battery charger failure?
An amber BATT CHGR FAIL (L or R) CAS
What will selecting the L BUS TIE switch to the ISLN position do?
Isolates the L MAIN AC bus from all power sources except the left IDG
What is an IDG and how does it work?
Integrated Drive Generator - It operates like a constant speed transmission. As the engine speed changes, the CSD maintains the generator at a constant speed
What is the function of the L and R MAIN TRU switches?
The on-side MAIN AC BUS powers each main TRU. In the unlikely event that the on-side MAIN AC BUS should fail, the L or R MAIN TRU switch can be selected to the opposite side MAIN AC bus to restore the TRU and its respective MAIN DC bus
If using a L or R MAIN TRU switch, what will happen to the failed side ESS DC BUS?
Powered automatically by the AUX TRU
How is the electrical power control panel normally configured?
5 in, 5 out
In what situation can a TRU power more than one bus, and which buses can it power?
When the HMG and L ESS / R ESS switches are IN/ON, the AUX TRU can power both ESS DC buses
If a ground service bus switch is selected ON with no external power connected to the aircraft, where will the GSB get its power?
Right battery
Whenever the external battery is turned on, what light turns on?
Lower beacon
What are two items that will cause one or both battery switch lights to illuminate even while one or more AC generators are operating?
Starting the APU or selecting the AUX HYD pump ON
