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AW > Electrical System > Flashcards

Electrical System Flashcards

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1
Q

What are the two types of electrical systems mentioned?

A

AC and DC systems

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2
Q

What happens if one electrical system fails?

A

The other system can supply power automatically via cross ties

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3
Q

What is provided in case of a complete loss of power?

A

An emergency generator and TRU

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4
Q

What does the emergency generator and TRU provide power to?

A

Emergency and essential bus

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5
Q

Where are warnings for electrical issues displayed?

A

On the annunciator panel

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6
Q

List some warnings that can appear on the annunciator panel.

A
  • Ten fail
  • Emergency ten bearing
  • TRU
  • AC or DC less bus failure
  • Over temp conditions
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7
Q

What voltage DC battery is provided for APU start?

A

24 VDC

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8
Q

What is the function of the receptacles for AC and DC external power?

A

To supply power on the ground

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9
Q

If AC power is used, what can the TRU do?

A

Convert AC to DC

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10
Q

What must be on to use AC power if only DC is used?

A

The generator

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11
Q

Where are most components of the electrical system housed?

A

Within the LH and RH forward pods

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12
Q

Where are most circuit breakers located?

A

On the PDP

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13
Q

Where are emergency generator feeder circuit breakers mounted?

A

On the emergency distribution panel in the aft fuselage

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14
Q

What is the power output of the AC generators?

A

40 KVA producing 200 volt 400 hz 3 phase power

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15
Q

What drives the AC generators?

A

AGB (Accessory Gear Box)

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16
Q

What is the function of the three place switch TEST/OFF/ON?

A

To control the generator output

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17
Q

What does the TEST position do?

A

Re-excites the generator coils and illuminates associated annunciator lights

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18
Q

What does the generator control unit (CU) monitor?

A

The output of the generator

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19
Q

What happens when frequency increases to 91% RRPM for more than 3 seconds?

A

The contractor closes to allow the generator to produce power

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20
Q

What causes the GEN 1 FAIL or GEN 2 FAIL lights to illuminate?

A

When the generator is disconnected

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21
Q

What is the AC power distribution system composed of?

A
  • 115/200 v 3 phase main AC bus
  • 115/200 v 3 phase essential bus
  • 115 v single phase AC navigation bus
  • 26 v AC instrument bus
  • 26 v AC navigation bus
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22
Q

What happens if the supply to essential busbars fails?

A

The emergency generator will pick up the load

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23
Q

What do the two AC step-down transformers provide power to?

A

Two 26 volt AC instrument busbars and the 26 volt AC navigation bus

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24
Q

What happens when both generators are on?

A

Each powers its own system through its main line contractor

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25
What does the cross tie contractor do when one generator fails?
Connects the busbar with the opposite 3 phase busbar
26
What protects the opposite 3 phase bus bar?
AC BUS TIE circuit breaker
27
What happens if the AC BUS TIE circuit breaker is open?
You lose the connection to the opposite bus bar
28
What is the function of the NO. 1 AC ESS BUS FAIL RELAY?
It indicates a failure in the NO. 1 AC essential bus ## Footnote The relay senses issues in the essential bus and impacts the operation of the associated systems.
29
What voltage does the 115/26V STEP DOWN TRANSFORMER provide?
It provides 115V and 26V outputs ## Footnote This transformer is essential for stepping down voltage for various systems.
30
Where is the Nav bus changeover switch located?
On No 2 PDP ## Footnote PDP stands for Power Distribution Panel.
31
What does setting the Nav bus changeover switch to position 2 do?
De-energizes the 26 volt AC bus fail relay ## Footnote This action affects the operation of the nav bus changeover relay.
32
What does the AC ESS BUS caution light indicate?
The associated essential bus is de-energized ## Footnote The light is part of the annunciator panel and alerts the crew to system statuses.
33
What type of power does the emergency generator provide?
200-volt, 400 Hz 3 phase AC ## Footnote This power is crucial for emergency operations.
34
What is the capacity range of the emergency generator?
6-7.5 KVA ## Footnote The generator is mounted on the oil cooler fan gearbox.
35
How is the emergency generator activated?
By setting the EMERG GEN switch to TEST or FLT ## Footnote The switch position allows the generator control unit to energize the generator under specific conditions.
36
What does the emergency TRU provide?
28 VDC ## Footnote TRU stands for Transformer Rectifier Unit.
37
What happens when the emergency generator is operational?
It powers the emergency 3 phase AC bus ## Footnote This ensures essential systems maintain functionality in emergencies.
38
Fill in the blank: The changeover is indicated by a momentary _______ warning flag on nav instruments.
power off ## Footnote This warning helps identify system status during changeover.
39
What happens when the main generator fails?
The essential bus fail relays operate to connect the emergency AC bus to both AC ESS BUS and energize them.
40
What occurs if a second TRU fails?
The DC bus contractor will operate to connect the DC output of the emergency TRU to both DC ESS BUS and energize.
41
What is the status of the emergency generator when in flight and rotors are turning?
The emergency generator is rotating but not creating power.
42
What does the emergency generator do when a main generator or TRU fails?
Goes to standby mode, develops power, energizes the emergency AC bus, emergency TRU, and turns on the EMERG GEN READY annunciator.
43
What happens if a second main generator or TRU fails?
The emergency generator will energize the associated AC or DC nav buses.
44
What does the TEST position do?
Bypasses control circuits and energizes the emergency generator, applying power to the emergency bus.
45
What is indicated by the EMERG GEN READY capsule on the annunciator panel?
The emergency generator is ready and applied power to the emergency bus.
46
What is the purpose of the AC external power receptacle?
To connect 200 V, 3 phase, 400 Hz power.
47
What does the external power monitor check for?
Over voltage, under voltage, and proper phase rotation.
48
What happens if the external power is not within specs?
It will trip the external power contractor and prevent application of power.
49
What is the function of the reset switch in the external power compartment?
Must be applied after a trip before getting power.
50
What is the voltage and capacity of the TRUs in the DC system?
2 TRUs supply 28 volts and 200 amps.
51
What happens if one TRU fails?
A bus tie relay connects the two DC ESS BUS bars automatically.
52
What powers the emergency and essential DC buses if both TRUs fail?
The emergency generator will energize automatically.
53
What is the function of the sealed lead acid battery?
Normally used to start the APU and can be used for limited emergency DC power if all other DC power is lost.
54
List the components of the DC power distribution system.
* 26 VDC Bus * 26 VDC Essential bus * 24 VDC Emergency DC bus * 24 VDC Hot battery bus
55
What happens when either TRU fails or is turned off?
You will get a TR1 FAIL or TR2 FAIL action light.
56
What is the role of the DC cross tie?
Automatically connects the failed DC bus bar to energized DC busbar.
57
What energizes the hot battery bus?
The 24 VDC battery whenever the battery is connected and the battery switch is on.
58
Fill in the blank: The emergency generator will be energized automatically but will not provide power until the failure of the _______.
second TRU
59
What does the reverse current cutout bypass circuit do?
Connects the battery directly to the No. 2 DC bus if the reverse current cutout relay and the No. 1 DC bus fail. ## Footnote This circuit ensures continuous power supply in case of relay failures.
60
What activates the reverse current cutout bypass relay?
When the No. 1 RU fall relay and the reverse current cutout fail relay close. ## Footnote This activation allows connection of the DC EMERGENCY BUS to the No. 2 DC ESS BUS.
61
What is the function of the TRU control switches?
Connect the TRU to the 3 phase AC. ## Footnote These switches are located in the overhead panel.
62
What happens when the battery switch is on?
Energizes the battery relay through the closed contacts of the emergency battery lockout relay. ## Footnote This allows the battery to energize the DC emergency bus.
63
What do the TR1 and TR2 HOT caution lights indicate?
Indicate that the internal temperature of the TRU exceeds 150°C. ## Footnote The lights are controlled by a temperature-sensitive bi-metallic switch.
64
What does the battery hot and off annunciator indicate?
Indicates that the battery has been turned on or off. ## Footnote This is specific to lead-acid batteries; NiCad batteries have different indicators.
65
What happens when the DC essential bus is de-energized?
The associated essential bus fail relay is de-energized, applying ground to the DC ESS BUS capsule on the annunciator panel. ## Footnote This action illuminates the associated light on the panel.
66
What is the rating of the emergency TRU?
28 volts, 100 amperes. ## Footnote This rating is crucial for emergency power supply.
67
What occurs if one TRU fails?
It energizes the emergency TRU. ## Footnote If both TRUs fail, both DC essential bus contactors are energized.
68
What does the associated contractor do when both TRUs fail?
Causes the external power contractor to open and DC power to be supplied from the TRUs. ## Footnote This ensures power supply continuity from the TRUs.
69
True or False: DC external power will provide power to the hot battery bus.
False. ## Footnote A depleted battery cannot start the APU with just DC external power.
70
Fill in the blank: The reverse current cutout bypass circuit connects the battery to the _______.
No. 2 DC bus. ## Footnote This connection is made when certain relay failures occur.

AW (7 decks)

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