CAA Module 11 > Module 11.6 Electrical power > Flashcards

Module 11.6 Electrical power Flashcards

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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
What are some advantages of lithium-ion batteries over Nickel-cadmium?
- High V and I production - Improved power quality - Quick recharge - 30% lighter - Compact - No memory degradation
26
A dc generator is required to supply a constant voltage with set limits under what conditions?
- Full range of engine speeds - No loads up to full loads - Share the load with other Gens
27
What is shown on the generator identity plate?
Direction of rotation
28
What is the purpose of the equalising coils?
Equalise the output between the two IDG's that are in parallel
29
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?
Load shed
30
When will the bus tie bars connect?
When the output on both the IDG's are at equal output, load sharing will then begin
31
What are some AC sources?
- AC generators - Static inverters - Rotary inverters
32
What can be altered in a rotating field alternator to boost the output?
- Magnetic field strength - Speed of rotation
33
What does the Generator Control Unit (GCU) control?
- Voltage over/under - Frequency over/under - Phase over/under
34
What is "AC wild"?
Faster the rotor turns the higher the output frequency
35
How is a constant frequency output achieved?
By using Constant Speed Drive Units (CSDU)
36
Where is the CSDU?
It is located between the engine's auxiliary gearbox and the Integrated Drive Generator (IDG)
37
When the engine speed changes the GCU sends a signal to what?
CSDU
38
What is the purpose of the oil circuits in the CSDU?
Cooling and lubrication
39
What are the two CSDU monitoring indications?
- Absolute oil temperature - Rise in temperature
40
When will the CSDU go into under speed?
When the engines are at higher speeds than the frequency needed for AC
41
How is the CSDU disconnected?
Input disconnected by electrically actuated device
42
What will show that the CSDU disconnection was successful?
On the ECAM/EICAS panel the voltage and frequency will display 0
43
When can the CSDU be reconnected?
When the aircraft is on the ground and the engines are stopped
44
What does CSDU do?
Variable engine RPM to a constant generator speed of 2000 rpm
45
What are the only power sources that can be parallel?
IDG's
46
What does a current transformer do?
Measures the current without having to break into the system 'amp clamp'
47
What angle are the phases apart in a 3 phase ac generator?
120°
48
What are the 2 electrical supplies in an emergency?
- RAT - Battery
49
What is the ac frequency and voltage controlled by?
Generator Control Unit (GCU)
50
What will be connected to the essential bus?
All things necessary to ensure safe flight
51
For one pole to get 12,000 output it must be spun at 24,000 rpm. - Two poles? - Three poles?
Two poles - 12,000 rpm Three poles - 8,000 rpm
52
What are two types of electrical protection?
- Fuses - Circuit breakers
53
What are the only cables that aren't protected by breakers or fuses?
IDG feeder cables, they are instead protected by the electrical circuits in the GCU
54
How are fuses checked?
Using a multimeter
55
When must spare fuses be available?
Inflight
56
How many times can a CB be reset inflight?
Once
57
What CB's are in reach of the pilot?
Only the essential ones
58
When do CB's and fuses trip or blow?
When there is an overload or a short circuit
59
How do you know a CB has popped?
White band/collar will be visible
60
What type of CB's are used in modern aircraft?
Virtual
61
What are the 6 pins in an AC external power connector?
Pin A - Phase A Pin B - Phase B Pin C - Phase C Pin D - Neutral Pin E - Interlock pin Pin F - Interlock pin
62
What can be said about the interlock pins?
Make last and break first
63
How many pins are in DC external power connector?
There are 3, positive, negative and neutral
64
In the CSDU, when will the oil circulate the unit?
When the CSDU is in over drive or under drive
65
What is the problem with the CSDU running in Straight drive?
The oil valves are closed, this means that there is no cooling or lubrication. This is undesirable
66
What drive mode are CSDU's typically designed to be in for long stretches inflight? i.e. During cruise
Under drive
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