Electrical Flashcards
What is the minimum acceptable battery voltage when performing a battery
integrity check?
22 volts DC
What is the voltage and ampere rating of the batteries?
24 volts DC
40 ampere-hours
With the battery switches selected ON and no other power on the aircraft,
which electrical buses are shown as powered on the EPMP?
Essential DC bus (powered by the batteries)
Essential AC bus (powered by the “E” inverter)
With the battery power selected “ON” and no other power sources available,
what are the acceptable readings for the Essential AC and DC bus volts?
Essential AC bus – 115 volts AC, 400 Hz
Essential DC bus – 22-27 volts
What buses are powered with either external battery switch selected ON?
Only the essential buses
ESS- DC = batteries, ESS AC bus (Phase A only) through the “E” inverter
Where can information be found concerning items powered by the emergency
batteries?
QRH, Electrical System Abnormal Procedures tab (EA)
How are the emergency batteries normally tested?
Arm the emergency battery switch with no other power on the aircraft
Where are the feeder bus circuit breakers located?
On the power distribution box (PDB), in the right radio rack
How is AC external power connected to the aircraft?
Select the AUX PWR switch ON with at least 1 battery switch ON
- What is the function of the battery override switch on the AC external power
receptacle?
To connect AC power to the aircraft if the batteries are discharged or removed
- What buses are powered with external DC power connected?
All DC buses are powered ( ESS – DC, LEFT & RIGHT MAIN DC), and the ESS AC bus (Phase A only) through the “E” inverter
- What buses are powered with external AC power connected?
All buses are powered AND the batteries will be charged
Is it possible to charge the batteries using DC external power?
No, the respective MAIN AC buses must be powered in order to charge the
batteries
- What is the output rating of the “E” inverter?
800 volt-amps
- What is a valid indication of “E” inverter operation?
Essential voltmeter switch-light selection on the EPMP and indications of
115 volts, 400 Hz
- What buses are powered by the “E” inverter?
Essential AC bus, phase “A” only
- What are the possible sources of power for the “E” inverter?
Whatever is powering the Essential DC bus
The standby electrical power system (HMG)
- What are the 2 main functions of the battery chargers?
To charge their respective battery
To provide a transformer-rectifier mode of operation for supplemental power if
necessary
- What buses supply power to the battery chargers?
Battery charger #1 (left) – LEFT MAIN AC BUS
Battery charger #2 (right) – RIGHT MAIN AC BUS
- Can one battery charger charge both batteries?
No, only its respective battery
- What is the maximum output of the battery chargers in transformer-rectifier
mode?
50 amps each, for a total of 100 amps
- What situations would cause the battery chargers to operate in transformer-
rectifier mode?
When the AUX hydraulic pump is selected on, or
APU start button is depressed, or
Selection of ESS DC Bus Battery Switch to “ON” (Manually or Automatically)
- What is the output of the converters?
AC output – 115 volts AC at 400 Hz, 23 KVA
DC output – 28 volts DC, 250 amps thus 28 X 250 = 7000 VA or & KVA
- If a converter failure occurs, what are the resulting indications?
The respective “AC POWER FAIL” and “DC POWER FAIL” amber CAS messages
will illuminate
The affected AC and DC buses will automatically switch over to the next available
power source
- What is the difference in the corrective action for a “DC POWER FAIL” CAS
message versus an “AC POWER FAIL” CAS message?
If a “DC POWER FAIL” CAS message illuminates, converter operation may be
continued and monitored
If an “AC POWER FAIL” CAS message illuminates, the converter must be turned
OFF because the cooling fans require AC power to operate
- If an amber “CONV FAN FAIL” CAS message occurs, what does this in?
At least one of the 5 converter fans have failed
- Is converter operation permitted with a converter fan inoperative?
Yes, for a designated period of time (25 hours)
- What is the immediate consideration with a dual converter failure in flight?
NAACP
Symbol generator
N- normal
A- alternate
A- alternate
Fuel
C- cross flow open
P- single pump operation
- What is the engine-driven alternator output?
115 volts AC, 3-phase, 30 KVA
- Control of electrical current and auto-switching for AC and DC is supplied
from what components?
AC and DC bus power control units (BPCUs)
- When might you use the standby electrical power system?
With Dual Converter Failure above 15,000 feet until you are able to start the APU
alternator as a source of electrical power
With an ESS DC Bus on battery power fault
32. What is the minimum HP % RPM to consider when using the standby electrical power system (HMG)?
67% HP RPM
- What are the considerations regarding the use of the SEPS for landing?
Do not use thrust reversers
Do not use automatic ground spoilers (They will not be available with loss of Left
Main DC)
Maintain a minimum of 67% HP RPM (Engines will remain at 67% with loss of
Main DC)
Deploy the speedbrake handle slowly upon landing
Turn the emergency batteries ON as a backup
Landing Gear extension may cause the SEPS to go off line
Be prepared to cycle the SEPS switch if it cycles off line
- What buses are powered when using the SEPS?
Essential DC bus (through the TRU)
Essential AC bus, phase “A” only (through the “E” inverter)
- During SEPS operation, why might the utility pump operate continuously if it
is armed?
Because the control circuit is on the L MAIN DC bus, which may no longer be
powered (utility solenoid shutoff valve fails to the OPEN position)
- What is the function of the TRU?
To convert AC power into DC power. Power the Left, Right Main DC and ESS DC
buses during APU / EXT AC power operations, and power ESS DC bus during
SEPS operations. It also acts as a backup to the DC converters in-flight.
- What is the maximum output of the TRU?
300 amps
- Where does the EPMP receive its power from?
From the remote power supply (RPS)
- On the EPMP, the left and right voltmeter selector switches allow the
monitoring of what components?
The left and right converters
- The “ESS” power monitor switch on the EPMP, when selected, provides
display information about which electrical power sources?
Essential DC and Essential AC bus voltages
- Why are the six EPMP “AUTO” bus switches selected under normal flight
conditions?
To allow the bus power control units (BPCUs) to select the best available power
source for each bus
- What is the normal power source for the Essential DC bus after engine start
with both converter switches selected ON?
Whatever power source is providing power to the left main DC bus (normally the
DC portion of the left converter)
- What is indicated by the battery ammeters on the EPMP?
Battery charge and discharge in amps
- What is indicated by an amber “EPMP POWER FAIL” CAS message?
At least one of the 4 input power sources to the remote power supply (RPS) has
failed
- With a left converter failed, what is most likely power source for the L MAIN
DC bus?
The TRU
- What power source normally provides power to the ESS DC bus in flight?
The DC portion of the left converter, through the L MAIN DC bus
- What power source normally provides power to the ESS AC bus in flight?
The AC portion of the left converter, through the L MAIN AC bus
- What is indicated by an amber AC or DC reset light?
A fault on an AC or DC bus
- Is it possible to start the APU using external DC power?
Yes, but the QRH must be referenced: Follow “APU” Starting using external
DC power procedures in QRH in the APU operation (NB section)
- If the APU is running and the AUX PWR switch is selected ON, what would
happen if both battery switches were selected OFF?
No change would occur, the APU alternator would continue to provide power to
the main and essential buses
- What is the maximum allowable AC AUX PWR load indication prior to starting
the TAY engine?
35 percent
- If the ESS DC BUS AUTO, LEFT MAIN and BATT switch light capsules are
illuminated simultaneously in flight, what likely has occurred?
The K20 / K22 relay has experienced a failure of one of the relay poles,
report for maintenance action
