Electrical Flashcards
If a circuit breaker is open, when should it be reset?
If the affected component is required for safe flight and landing
A No-Break Power Transfer (NBPT) can only occur between an APU generator and:
An Engine Driven Generator (IDG)
The two bus tie isolation contactors are controlled by the:
Switches on the cockpit overhead panel, generator control units (GCUs), and Bus Power Control Units (BPCUs)
Speed brake consideration when the standby electrical power system (HMG) is in operation:
May be used provided operation is slow (3 seconds for full movement)
If the R GEN switch indicates an AMBER OFF light, what is indicated?
The IDG has been isolated by the BPCU
If the L MAIN TRU switch is selected to the R AC position, what happens?
The L MAIN TRU will receive power from the R MAIN AC bus
During normal operations (IDGs powering the aircraft), the Ground Service Bus receives power from which bus?
Right Main DC bus
When does the “ARM” position of the Emergency Power System switches allow the emergency power system to activate?
Essential DC bus < 20 VDC
If one battery charger fails, what happens?
Amber BATT CHGR FAIL (L or R)
If the HMG is selected on due to inop generators and APU, what buses will be powered?
Both Standby AC buses, Both ESS DC buses and the ESS AC bus
The E-Inverter can receive power from what bus?
Left or Right ESS DC buses
The AUX TRU is capable of providing power to both the left and right ESS DC buses during what operations?
HMG
Where do the battery chargers receive their power?
From the respective Main AC Bus
What will selecting the L Bus tie switch to the ISLN position do?
Isolates the L MAIN AC Bus from all power except the left IDG
How many emergency batteries are installed in the airplane?
Four, located in the LEER, REER and BEER(AEER)
How are the emergency batteries charged?
Left - L STBY AC Bus
Right - R STBY AC Bus
Forward Lighting - L MAIN AC Bus
Aft Lighting - R MAIN AC Bus
What minimum battery voltage will cause the E-BATTs to come on?
< 20VDC
What is the minimum main battery voltage? (For APU start?)
22 VDC
Below what voltage would the main batteries require a deep cycle recharge?
< 7 VDC
How long does it normally take for a battery deep cycle?
24 hours
If the batteries actually fell to 20 volts, how long would it take to fully recharge?
90 minutes
What 3 events will illuminate the battery switch lights?
- When L&R batteries are powering the L&R Essential DC Bus
- When the AUX HYD PUMP is ON
- During APU Start
Which battery is used to close the main door from the outside door switch?
Right Battery, which is wired to the main door switch
What is an IDG and how does it work?
Integrated Drive Generator - constant speed drive maintains the generator at a constant speed as the engine speed changes
What is the rating of the HMG?
10 kVA
How is the HMG powered?
Left hydraulic system pressure or PTU (provided there is fluid in the system)
What will the HMG power?
L&R STBY AC Bus and AUX TRU
How many TRUs are on the aircraft?
5 Total
L&R ESS TRU
L&R MAIN TRU
AUX TRU
What is the function of the L&R MAIN TRU switches?
If the onside AC Bus should fail, the opposite side AC bus can be selected to power the MAIN TRU on the failed side.
If a MAIN AC Bus has failed, and the MAIN TRU selected to get power from the operative side, what will power the ESS DC bus on the failed side?
AUX TRU
How should the electrical control panel normally be set up (switch positions)?
5 In, 5 Out, Batteries Charging
What will cause the E-BATTs to come on automatically if armed?
If either ESS DC Bus voltage drops below 20 VDC
How many TRUs are normally operating in-flight?
5 - Main & Essential run continuously while the AUX operates in standby
Which TRU is not dedicated to a single bus?
AUX TRU
In what situation can a TRU power more than one bus?
When the HMG and L ESS / R ESS switches are ON, the AUX TRU can power both essential DC buses
If the right main TRU fails, what should automatically power the R MAIN DC bus?
AUX TRU
If a generator fails, will you get a break-power or no-break-power transfer?
Break Power Transfer
If a generator is selected off while running, will you get a break power or no break power transfer?
No-Break Power Transfer
If a running engine is shut down with the fuel control switch, will you get a break power or no break power transfer?
No Break Power Transfer
If an engine fails, will you get a break power or no break power transfer?
Break Power Transfer
If a ground service bus is selected on, what will power that bus if there’s a DC cart connected to the aircraft?
External DC Power
If a ground service bus switch is selected ON with no external power connected, where does the bus get its power?
Right Battery
In flight, the ground service bus is normally powered by what bus?
R MAIN DC Bus
Whenever the ground service bus is turned ON, what else comes on?
Lower Beacon
Whenever the external battery is turned ON, what else comes on?
Lower Beacon
Which batteries are activated when the external battery switch is turned ON?
Both Main Batteries
What are two items that can cause one or both battery lights to come on even while one or more AC generators are operating?
Starting the APU, or selecting the AUX HYD Pump ON
What item will be lost with only one AC power source operating in flight?
Galley Power
What items are capable of being powered from the battery tie bus?
AUX HYD Pump
APU Starter
ESS DC Busses
