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M11 > 11.6 Electrical Power > Flashcards

11.6 Electrical Power Flashcards

1
Q

Approximately how much power do 2 and 4 engine aircraft use?

A
  • 2 engines = 100 kilowatts

- 4 engines = 400 kilowatts

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2
Q

What does the electrical power system consist of and what does each part do? [2]

A
  • Generation subsystem - produces electrical energy

- Distribution subsystem - provides to consumers

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3
Q

What device converts from AC to DC?

A

TRU - Transformer Rectifier Unit

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4
Q

What device converts from DC to AC?

A

Static Inverter

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5
Q

What are the 5 AC power Supplies?

A
  • Engine driven generator
  • APU generator
  • External Power
  • Emergency Generator
  • Static Inverter
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6
Q

What do AC consumers mainly consist of? (3)

A
  • Heating
  • Lighting
  • Mechanical equipment
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7
Q

What voltage is AC power provided at?

A

115V

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8
Q

What frequency is AC power provided at?

A

400 hertz

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9
Q

What batteries are used on aircraft?

A

Nickel Cadmium

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10
Q

What do batteries provide power for? [3]

A
  • Emergency distribution
  • APU starting
  • Engine start
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11
Q

What are the 3 parts AC/DC power distribution is divided into?

A
  • Main Power Distribution
  • Essential Power Distribution
  • Emergency Power Distribution
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12
Q

What does AC power distribution Consist of? [3]

A
  • Main AC busses
  • Power Source Switching
  • Bus Tie Switching
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13
Q

What does a bus do and what does it consist of? [2]

A
  • Connects the power source to all electrical consumers that use the same type of electrical power
  • Consists of a low resistance electrical connection between all wires connected
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14
Q

What voltage does DC power run at?

A

28 volts

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15
Q

What is the definition of “main power distribution”?

A

Provides electrical power to all main consumers

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16
Q

What is the definition of “essential power distribution”?

A

Supplies all consumers that are essential to operate the aircraft safely

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17
Q

What is the definition of “emergency power distribution”?

A

Supplies the consumers that necessary to land safely

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18
Q

What are the 4 types of AC consumers?

A
  • single phase consumers
  • voltage different from 115v
  • 3 phase consumers
  • large loads
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19
Q

What must happen to large loads before any power source is switched on or off?

A

Large loads must be switched off prior to power on or off

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20
Q

What does load shedding do?

A

Improves the reliability of power relays and prevent overloads of power source

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21
Q

What are the power relays controlled by? (2)

A
  • Generator control unit (GCU) or,

- Ground power control unit (GPCU)

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22
Q

When will auto switching happen?

A

When voltage and frequency “Ok” and no failures

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23
Q

What systems may fall under “essential power distribution”?

A

Captain navigation and communication equipment and important control and warning systems

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24
Q

How long does the aircrafts battery provide sufficient electrical energy?

A

30 minutes

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25
Q

What electrical energy can the battery provide in an emergency situation?

A
  • 24v DC directly to the DC emergency bus

- 115v AC after conversion at the static inverter to the AC emergency bus

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26
Q

For long range aircraft, what must be installed in case of emergency?

A

Emergency generator

27
Q

What 2 emergency generators are there?

A
  • air driven generator

- constant speed motor generator

28
Q

What are the main distribution components? (3)

A
  • power relays used as switching devices
  • circuit breakers and fuses
  • Current transformers
29
Q

What 2 types of powers relays are used for AC switching?

A
  • Contactors

- breakers

30
Q

What is the main function of a fuse or circuit breaker?

A

To prevent an overheat or fire due to a short circuit

31
Q

What happens to a fuse if the current exceeds the maximum allowed value?

A

The metal strip melts and electrical circuit interrupted

32
Q

What are the two advantages of circuit breakers over fuses?

A
  • reset quickly

- used as manual on/off switches to allow for deactivation of circuits

33
Q

What do regulations specify about the location of circuit breakers for essential loads?

A

Should be within reach of the pilots during flight

34
Q

What colour collars are used to identify circuit breakers for specific activities? (Crew and maintenance)

A
  • orange (crew)

- grey (Maintenance)

35
Q

What can be used to prevent a circuit breaker being closed because of a missing component?

A

Red safety clips

36
Q

What can be used to stop circuit breakers being closed during maintenance procedures?

A

Red safety tags

37
Q

What does circuit breaker monitor help with?

A

Identifying a tripped circuit breaker via a caution message on the ECAM

38
Q

What are the two methods of AC power generation?

A
  • generator

- static inverter

39
Q

How does a basic generator work?

A

With a rotating magnet, producing a magnetic field inducing voltage in the coil of the stator, (induction with motion)

40
Q

In a generator, what does the amount and polarity of generated voltage depend on?

A

The angle of the rotating magnet

41
Q

What is one complete rotation of the magnet equal to?

A

One complete sine wave

42
Q

How is the frequency of a generator influenced?

A

By the rotational speed of the magnet, and the amount of pole pairs

43
Q

What does 3 phase stator coils generate?

A

Individual voltages

44
Q

What keeps the output voltage and frequency from the engine to the generator, constant?

A

Constant speed drive

45
Q

What components does a constant speed drive consist of? (3)

A
  • Differential gear
  • hydraulic motor/pump combination
  • speed control circuit
46
Q

How is the constant speed drive or integrated drive generator mounted on the engine gearbox?

A

Quick attach and detach rings

47
Q

What do TRU’s convert?

A

3 phase 115v AC to 28v DC

48
Q

What does the number of batteries required depend on?

A

The amount of electrical energy that needs to be stored

49
Q

What are the advantages of using nickel cadmium batteries over lead acid type batteries?

A
  • Less maintenance costs

- Low temperature performance

50
Q

On average, how often must the battery conditions be check?

A

Approx every 2000 operating hours

51
Q

What does a battery condition check contain? (2)

A
  • Storage capability

- electrolyte condition

52
Q

What are the advantages of lithium-ion batteries over nickel cadmium? (6)

A
  • high voltages and high current production
  • improved power quality
  • ability to recharge quickly
  • weigh 30% less
  • compact size
  • no memory degradation
53
Q

How many stages does li-ion batteries charge in? And what are they?

A

3 stages

  • constant current
  • balance
  • voltage source
54
Q

What does the constant current charge stage do for li-ion batteries?

A

Charger applies constant current at a steadily increasing voltage until voltage limit reached for each cell

55
Q

What does the balancing stage of charging for li-ion batteries do?

A

Reduces the current whilst the state of charge for each cell is brought to the same level until the battery is balanced

56
Q

What may an overcharged or overheated li-ion batteries suffer from?

A

Thermal runaway or cell rupture

57
Q

What methods can ground power be supplied? (2)

A
  • External power source

- apu generator

58
Q

What are the two types of external ground power?

A
  • fixed station

- moveable cart

59
Q

What does the plug of a receptacle consist of?

A
  • 4 thick pins (to provide the connection for 3 phase and a common neutral)
  • 2 shorter pins (control the connection)
60
Q

When de-energising the aircraft from external power, what must be checked? (3)

A
  • Electrical loads to a minimum
  • consumers switched off as they will switch to battery power
  • main battery switches and emergency power switches off
61
Q

What bus does external power use?

A

Ground service bus

62
Q

What does the ground service bus supply?

A

Equipment for loading/unloading, cleaning and cabin and cargo doors

63
Q

What is the only power source during towing?

A

Battery

M11 (22 decks)

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