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CAA Module 11 > Module 11.6 Electrical power > Flashcards

Module 11.6 Electrical power Flashcards

1
Q

What are the electrical voltages mainly used on an aircraft?

A
  • 115/200 Vac
  • 28 Vdc
  • Batt 24 Vdc
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2
Q

What does the electrical power system consist of?

A
  • Generation systems
  • Distribution systems
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3
Q

What is used to convert AC to DC from the IDG?

A

Transformer Rectifier Units (TRU)

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4
Q

What are some electrical sources on an aircraft?

A
  • APU
  • GPU
  • RAT
  • IDG
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5
Q

What are aircraft batteries used for?

A
  • Emergency power
  • APU start motor power
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6
Q

When are the batteries charged?

A

During normal operation of the electrical power system

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7
Q

How is dc converted to ac?

A

Static inverter

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8
Q

What is the dc power source inflight?

A

IDG but then converted to dc via the TRU’s

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9
Q

Why are the batteries semi-sealed (vented)?

A

To allow gases to escape and prevent spillage of the electrolyte

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10
Q

Are secondary cells rechargeable?

A

Yes they are

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11
Q

In an emergency how long must the battery supply power for?

A

30 mins

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12
Q

Where are batteries vented to?

A

Overboard, there is a non return valve to prevent reverse flow

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13
Q

What is the purpose of a battery tray?

A

To collect any spilt electrolyte

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14
Q

What are the two types of batteries that may be used on an aircraft?

A
  • Lead acid
  • Nickel-Cadmium
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15
Q

What voltage are individual cells:
- During charging?
- During discharging?

A

Charging - 1.5V
Discharging - 1.0V when fully discharged

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16
Q

What should battery checks consist of?

A
  • Storage condition
  • Electrolyte condition
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17
Q

How is the charge level checked on a Ni-cad battery?

A

Only possible by monitoring the voltage and the current during charging

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18
Q

What batteries are highly susceptible to thermal runaway?

A

Nickel-cadmium

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19
Q

What are the two charging methods?

A
  • Constant current
  • Constant voltage
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20
Q

What type of battery uses constant current charging?

A

Nickel-cadmium

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21
Q

What are batteries monitored for?

A

Their temperature

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22
Q

When is the hot battery bus connected to the battery?

A

Always

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23
Q

Where would electrical info be displayed?

A

On the ECAM/EICAS

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24
Q

When removing and installing a battery, what order are the leads connected/disconnected?

A

Removal
- Neg first
Install
- Neg last

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25
Q

What are some advantages of lithium-ion batteries over Nickel-cadmium?

A
  • High V and I production
  • Improved power quality
  • Quick recharge
  • 30% lighter
  • Compact
  • No memory degradation
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26
Q

A dc generator is required to supply a constant voltage with set limits under what conditions?

A
  • Full range of engine speeds
  • No loads up to full loads
  • Share the load with other Gens
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27
Q

What is shown on the generator identity plate?

A

Direction of rotation

28
Q

What is the purpose of the equalising coils?

A

Equalise the output between the two IDG’s that are in parallel

29
Q

In the event of a failure of one generator system, what should be done before the working generator bars the load of the faulty one?

A

Load shed

30
Q

When will the bus tie bars connect?

A

When the output on both the IDG’s are at equal output, load sharing will then begin

31
Q

What are some AC sources?

A
  • AC generators
  • Static inverters
  • Rotary inverters
32
Q

What can be altered in a rotating field alternator to boost the output?

A
  • Magnetic field strength
  • Speed of rotation
33
Q

What does the Generator Control Unit (GCU) control?

A
  • Voltage over/under
  • Frequency over/under
  • Phase over/under
34
Q

What is “AC wild”?

A

Faster the rotor turns the higher the output frequency

35
Q

How is a constant frequency output achieved?

A

By using Constant Speed Drive Units (CSDU)

36
Q

Where is the CSDU?

A

It is located between the engine’s auxiliary gearbox and the Integrated Drive Generator (IDG)

37
Q

When the engine speed changes the GCU sends a signal to what?

A

CSDU

38
Q

What is the purpose of the oil circuits in the CSDU?

A

Cooling and lubrication

39
Q

What are the two CSDU monitoring indications?

A
  • Absolute oil temperature
  • Rise in temperature
40
Q

When will the CSDU go into under speed?

A

When the engines are at higher speeds than the frequency needed for AC

41
Q

How is the CSDU disconnected?

A

Input disconnected by electrically actuated device

42
Q

What will show that the CSDU disconnection was successful?

A

On the ECAM/EICAS panel the voltage and frequency will display 0

43
Q

When can the CSDU be reconnected?

A

When the aircraft is on the ground and the engines are stopped

44
Q

What does CSDU do?

A

Variable engine RPM to a constant generator speed of 2000 rpm

45
Q

What are the only power sources that can be parallel?

A

IDG’s

46
Q

What does a current transformer do?

A

Measures the current without having to break into the system ‘amp clamp’

47
Q

What angle are the phases apart in a 3 phase ac generator?

A

120°

48
Q

What are the 2 electrical supplies in an emergency?

A
  • RAT
  • Battery
49
Q

What is the ac frequency and voltage controlled by?

A

Generator Control Unit (GCU)

50
Q

What will be connected to the essential bus?

A

All things necessary to ensure safe flight

51
Q

For one pole to get 12,000 output it must be spun at 24,000 rpm.
- Two poles?
- Three poles?

A

Two poles - 12,000 rpm
Three poles - 8,000 rpm

52
Q

What are two types of electrical protection?

A
  • Fuses
  • Circuit breakers
53
Q

What are the only cables that aren’t protected by breakers or fuses?

A

IDG feeder cables, they are instead protected by the electrical circuits in the GCU

54
Q

How are fuses checked?

A

Using a multimeter

55
Q

When must spare fuses be available?

A

Inflight

56
Q

How many times can a CB be reset inflight?

A

Once

57
Q

What CB’s are in reach of the pilot?

A

Only the essential ones

58
Q

When do CB’s and fuses trip or blow?

A

When there is an overload or a short circuit

59
Q

How do you know a CB has popped?

A

White band/collar will be visible

60
Q

What type of CB’s are used in modern aircraft?

A

Virtual

61
Q

What are the 6 pins in an AC external power connector?

A

Pin A - Phase A
Pin B - Phase B
Pin C - Phase C
Pin D - Neutral
Pin E - Interlock pin
Pin F - Interlock pin

62
Q

What can be said about the interlock pins?

A

Make last and break first

63
Q

How many pins are in DC external power connector?

A

There are 3, positive, negative and neutral

64
Q

In the CSDU, when will the oil circulate the unit?

A

When the CSDU is in over drive or under drive

65
Q

What is the problem with the CSDU running in Straight drive?

A

The oil valves are closed, this means that there is no cooling or lubrication. This is undesirable

66
Q

What drive mode are CSDU’s typically designed to be in for long stretches inflight? i.e. During cruise

A

Under drive

CAA Module 11 (22 decks)

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