Electrical Flashcards

1
Q

What is the minimum acceptable battery voltage when performing a battery integrity check?

A

22 volts DC

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2
Q

What is the voltage and ampere rating of the batteries?

A

24 volts DC

40 ampere-hours

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3
Q

With the battery switches selected ON and no other power on the aircraft, which electrical buses are shown as powered on the EPMP?

A

Essential DC bus (powered by the batteries)

Essential AC bus (powered by the “E” inverter)

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4
Q

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?

A

Essential AC bus – 115 volts AC, 400 Hz

Essential DC bus – 22-27 volts

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5
Q

What buses are powered with either external battery switch selected ON?

A

Only the essential buses

  • ESS DC = batteries
  • ESS AC (Phase A only) through “E” inverter
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6
Q

Where can information be found concerning items powered by the emergency batteries?

A

QRH, Electrical System Abnormal Procedures tab (EA)

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7
Q

How are the emergency batteries normally tested?

A

Arm the emergency battery switch with no other power on the aircraft

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8
Q

Where are the feeder bus circuit breakers located?

A

On the power distribution box (PDB), in the right radio rack

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9
Q

How is AC external power connected to the aircraft?

A

Select the AUX PWR switch ON with at least 1 battery switch ON

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10
Q

What is the function of the battery override switch on the AC external power receptacle?

A

To connect AC power to the aircraft if the batteries are discharged or removed

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11
Q

What buses are powered with external DC power connected?

A

All DC buses are powered (ESS DC, L & R MAIN DC), and ESS AC (Phase A only) through the “E” inverter

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12
Q

What buses are powered with external AC power connected?

A

All buses are powered AND the batteries will be charged

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13
Q

Is it possible to charge the batteries using DC external power?

A

No, the respective MAIN AC buses must be powered in order to charge the batteries

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14
Q

What is the output rating of the “E” inverter?

A

800 volt-amps

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15
Q

What is a valid indication of “E” inverter operation?

A

Essential voltmeter switch-light selection on the EPMP and indications of 115 volts, 400 Hz

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16
Q

What buses are powered by the “E” inverter?

A

Essential AC bus, phase “A” only

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17
Q

What are the possible sources of power for the “E” inverter?

A
  • Whatever is powering the Essential DC bus

- The standby electrical power system (HMG)

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18
Q

What are the 2 main functions of the battery chargers?

A
  • To charge their respective battery

- To provide a transformer-rectifier mode of operation for supplemental power, if necessary

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19
Q

What buses supply power to the battery chargers?

A

Battery charger #1 (left) – LEFT MAIN AC BUS

Battery charger #2 (right) – RIGHT MAIN AC BUS

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20
Q

Can one battery charger charge both batteries?

A

No, only its respective battery

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21
Q

What is the maximum output of the battery chargers in transformer-rectifier mode?

A

50 amps each, for a total of 100 amps

22
Q

What situations would cause the battery chargers to operate in transformer-rectifier mode? (3)

A
  • When the AUX hydraulic pump is selected on
  • APU start button is depressed
  • Selection of ESS DC Bus Battery Switch to “ON” (Manually or Automatically)
23
Q

What is the output of the converters?

A
  • AC output – 115 volts AC at 400 Hz, 23 KVA
  • DC output – 28 volts DC, 250 amps
    thus 28 X 250 = 7000 VA or 7 KVA
24
Q

If a converter failure occurs, what are the resulting indications?

A
  • 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
25
Q

What is the difference in the corrective action for a “DC POWER FAIL” CAS message versus an “AC POWER FAIL” CAS message?

A
  • 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
26
Q

If an amber “CONV FAN FAIL” CAS message occurs, what does this indicate?

A

At least one of the 5 converter fans have failed

27
Q

Is converter operation permitted with a converter fan inoperative?

A

Yes, for a designated period of time (25 hours)

28
Q

What is the immediate consideration with a dual converter failure in flight?

A

NAACP

Symbol generator
N- normal
A- alternate
A- alternate

Fuel (This is primary, immediate consideration)
C- cross flow open
P- single pump operation

29
Q

What is the engine-driven alternator output?

A

115 volts AC, 3-phase, 30 KVA

30
Q

Control of electrical current and auto-switching for AC and DC is supplied from what components?

A

AC and DC bus power control units (BPCUs)

31
Q

When might you use the standby electrical power system? (2)

A
  • 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
Q

What is the minimum HP % RPM to consider when using the standby electrical power system (HMG)?

A

67% HP RPM

33
Q

What are the considerations regarding the use of the SEPS for landing? (7)

A
  • 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)
  • Landing Gear extension may cause the SEPS to go off line
  • Turn the emergency batteries ON as a backup
  • Be prepared to cycle the SEPS switch if it cycles off line
  • Deploy the speedbrake handle slowly upon landing
34
Q

What buses are powered when using the SEPS?

A
  • Essential DC bus (through the TRU)

- Essential AC bus, phase “A” only (through the “E” inverter)

35
Q

During SEPS operation, why might the utility pump operate continuously if it is armed?

A

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)

36
Q

What are the functions of the TRU? (4)

A
  • To convert AC power into DC power.
  • Power the Left, Right Main DC, and ESS DC buses during APU / EXT AC power operations.
  • Power ESS DC bus during SEPS operations.
  • Act as a backup to the DC converters in-flight.
37
Q

What is the maximum output of the TRU?

A

300 amps

38
Q

Where does the EPMP receive its power from?

A

From the remote power supply (RPS)

39
Q

On the EPMP, the left and right voltmeter selector switches allow the monitoring of what components?

A

The left and right converters

40
Q

The “ESS” power monitor switch on the EPMP, when selected, provides display information about which electrical power sources?

A

Essential DC and Essential AC bus voltages

41
Q

Why are the six EPMP “AUTO” bus switches selected under normal flight conditions?

A

To allow the bus power control units (BPCUs) to select the best available power source for each bus

42
Q

What is the normal power source for the Essential DC bus after engine start with both converter switches selected ON?

A

Whatever power source is providing power to the left main DC bus (normally the DC portion of the left converter)

43
Q

What is indicated by the battery ammeters on the EPMP?

A

Battery charge and discharge in amps

44
Q

What is indicated by an amber “EPMP POWER FAIL” CAS message?

A

At least one of the 4 input power sources to the remote power supply (RPS) has failed

45
Q

With a left converter failed, what is most likely power source for the L MAIN DC bus?

A

The TRU

46
Q

What power source normally provides power to the ESS DC bus in flight?

A

The DC portion of the left converter, through the L MAIN DC bus

47
Q

What power source normally provides power to the ESS AC bus in flight?

A

The AC portion of the left converter, through the L MAIN AC bus

48
Q

What is indicated by an amber AC or DC reset light?

A

A fault on an AC or DC bus

49
Q

Is it possible to start the APU using external DC power?

A

Yes, but the QRH must be referenced: Follow “APU” Starting using external DC power procedures in QRH in the APU operation (NB section)

50
Q

If the APU is running and the AUX PWR switch is selected ON, what would happen if both battery switches were selected OFF?

A

No change would occur, the APU alternator would continue to provide power to the main and essential buses

51
Q

What is the maximum allowable AC AUX PWR load indication prior to starting the TAY engine?

A

35 %

30 % at high elevation

52
Q

If the ESS DC BUS AUTO, LEFT MAIN and BATT switch light capsules are illuminated simultaneously in flight, what likely has occurred?

A

The K20 / K22 relay has experienced a failure of one of the relay poles, report for maintenance action