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ATPL Theory > AGK Electrics > Flashcards

AGK Electrics Flashcards

1
Q

Ohms law

A

V = IR

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2
Q

Power Equation

A

P = IV
P = IE
(E=EMF)

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3
Q

Lorentz law

A

F = BLI
Force= Field x Length x Current

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4
Q

CS25
CS23

A

Larger aircraft specifications
Smaller aircraft specifications

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5
Q

Emergency electrical configuration can power aircraft for how long ?

A

2 hours

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6
Q

Minimum battery power time for any aircraft ?

A

30 minutes

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7
Q

What electrical system is on A320 or B737

A

115/200 volt, 3 phase AC @ [400Hz]

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8
Q

Frequency on an A320 or B737

A

400 HZ constant

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9
Q

Capacitor impact on DC flow ?

A

Capacitors block DC Flow

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10
Q

Capacitance units ?

A

Farrads (F)

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11
Q

Resistors in series ?

A

Add up RT= R1+R2

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12
Q

Resistors in parallel ?

A

Add up in proportion 1/RT= 1/R1 + 1/R2
(Whether they want answer proportional to or not will vary with question)

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13
Q

Circuit flow direction in batteries ?

A

Conventional flow
(Positive to negative. Physically correct is negative to positive)

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14
Q

Shorter circuit means ?

A

Decreased resistance so therefore current increases

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15
Q

Circuit breaker and fuse role ?

A

To protect against over-currents

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16
Q

How are static discharge wicks attached to the aircraft ?

A

They are bolted to the wingtips
Max number you can lose is three

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17
Q

Why must aircraft components be electrically bonded ?

A

to prevent radio interference, Crackle or Hiss
Ensure a low resistance path to the static wicks

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18
Q

What is grounding ?

A

Removing charge from the airframe by connecting it into the ground to discharge, must be connected before re-fuelling commences

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19
Q

Cell structure ?

A

Two dis-similar metals and an electrolyte

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20
Q

Lead Acid battery voltages ?

A

Comprised of 6 cells.
Cell voltage = 2.2V offload
Terminal voltage = 12-12.6V (very small resistance means it isn’t exactly 2.2 x 6)
Nominal voltage = 12V

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21
Q

Modern batteries are ?

A

Nickel cadmium (Nicad)
Lithium Polymer (LiPo)
Lithium Ion (LiOn)

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22
Q

Modern battery voltages ?

A

comprised of 10 cells (jpn +1 spare)
Cell voltage = 1.3V on/offload
Terminal voltage = 13.2V
Nominal voltage = 12V

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23
Q

Biggest danger of modern batteries is ?

A

Thermal runaway.
Temperature increases, which causes resistance to decrease, which increases the current, which increases temperature and the cycle of continuously increasing temperature continues until completely submerged in water to cancel out all aspects.

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24
Q

Does thermal runaway only impact damaged batteries ?

A

No
Battery does not have the be damaged

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25
Q

Electrical pressure other names ?

A

Voltage
EMF
Potential difference

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26
Q

Batteries use ?

A

Chemical energy and produce DC

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27
Q

Generators produce ?

A

AC
(Alternator)

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28
Q

GEARB power sources ?

A

Power Priority Order
G-Generator
E-External power
A-APU
R-RAT
B-Battery

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29
Q

What are batteries rated in ?
(C-rating)

A

Amps per Hour (divisible by 100 or 10)
100 AH battery provides 100 Amps for 1 hour
or 1 Amp for 100 hours

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30
Q

Turning things off to reduce battery strain is ?

A

Load shedding

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31
Q

How to determine battery draw and load ?

A

Load shedding in conjunction with the Ammeter

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32
Q

Effect on batteries in series ?

A

The voltage increases - Current capacity of 1 battery
(Voltage is added together, capacity current stays the same)

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33
Q

Effect on batteries in parallel ?

A

The capacity increases - Voltage of 1 battery
(Capacity current is added together, voltage stays the same)

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34
Q
A
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35
Q

Battery rating is measured in ?

A

AH (Amperes per hour)

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36
Q

Effect of batteries in series ?

A

Voltage is added together
Has the current capacity of 1 battery

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37
Q

Effect of batteries in parallel

A

Current capacity is added together
Voltage is that of one battery

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38
Q

Rocker switches

A

Can usually be set in two or three positions

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39
Q

Push button switches

A

‘Toggle’ between stages, often have backlit text caption to indicate state

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40
Q

Rotary switches

A

Change resistance
Knob is arrow shaped to indicate selected option

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41
Q

Toggle switch

A

Can be visually determined if it’s on or off (state). Generally on is up.

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42
Q

Switches in positions where the could be accidentally knocked are often ?

A

Guarded (require genuine intent to alter)

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43
Q

Red guarded switch means ?

A

Irreversible action (generator disconnects)

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44
Q

Black guarded switch means ?

A

It’s a reversible action (Ditching switch)

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45
Q

Circuit breaker is ?

A

Re-settable

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46
Q

Fuse is ?

A

Replaceable (10% must be carried on board)

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47
Q

Circuit breaker and fuse function ?

A

To monitor current, therefore they can also monitor temperature.

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48
Q

How does a fuse work ?

A

a copper strip in a vacuumed glass tube connected to circuit with a current rating. If that rating is exceeded the copper will melt and disconnect the circuit.

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49
Q

When should you use a fuse of higher rating than required ?

A

Never

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50
Q

Types of circuit breaker ?

A

Thermo - temperature
Magnetic - current
Thermomagnetic - both

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51
Q

Efficiency’s of certain circuit breakers ?

A

Thermo breaker is good for slow current increase.
Magnetic breaker is good for rapid current increases
Thermomagnetic is good for both

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52
Q

Trip free breaker ?

A

Will not allow contacts to be closed if the fault persists

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53
Q

Non-trip free breaker ?

A

Can be held closed if the fault persists (Caution)

54
Q

Labelled trip breakers are known as ?

A

Tripped and tagged, do not reset

55
Q

When a magnet is fully magnetised it’s referred to as ?

A

Saturated, creating a Permanent magnet

56
Q

A magnet that can be fully magnetised and de-magnetised is known as ?

A

An electromagnet, and has a controllable Field.
Made from “soft” iron

57
Q

Electro-magnetic field relationship with current

A

Field is directly proportional to current .
(Field increase means current increase )

58
Q

Type of current in an Electro-magnet ?

A

DC current

59
Q

Relay role ?

A

Allows us to switch high voltage high current using low voltage low current

60
Q

How does a relay work ?

A

Uses an electromagnetic field generated by a coil wrapped round an iron core to close a switch in a high current circuit

61
Q

Solenoid process ?

A

Field is created when a current is applied and pulls inwards, compressing the spring. (Push and pull motion ) (like a punching fist)

62
Q

Electromagnetic induction is ?

A

When voltage current is generated in a conductor by it being moved across a magnetic field

63
Q

If wires are not shielded and a current flows through one, what will happen to close proximity wires ?

A

A current will begin to flow

64
Q

What is an Armature

A

Component where a current is produced when turned in a magnetic field.

65
Q

Require components for an AC generator, roles.

A

Rotor = Magnet (rotates)
Stator = Armature (stationary)

66
Q

DC generator components

A

Rotor = Armature
Stator = Magnet
Commutator (converts AC into DC by cancelling out bottom half of AC wave)

67
Q

Frequency formula ?

A

F = (pole x RPM) / 120

68
Q

AC waveform shape

A

Sinusoidal

69
Q

Most common frequency set up

A

4 poles, 400Hz = 12’000 RPM

70
Q

3 phase generator is called ?
+ produce

A

Polyphase
Creates a much larger and efficient field to directly feed the A/C

71
Q

What proportional determines generator output and how ?

A

Field strength,
As Field strength increases, so does current, therefore output is greater.

72
Q

How is current varied in response to load ?

A

Voltage regulator, it changes Feild strength in response to load demands

73
Q

How does a voltage regulator work ?

A

When an increase of output is required, the variable resistor decreases, so the DC source allows field strength to increased which then increases the output.

74
Q

Sense role ?

A

Monitors the output required and communicates with voltage regulator

75
Q

What does generator control unit control ?

A

Everything except the voltage regulator

76
Q

RMS / Vpeak calculation
(RMS is always stated, eg sockets is 240V)

A

RMS= Vpeak x 0.707

Vpeak= RMS / 0.707

77
Q

Tolerances for voltage and frequency

A

Voltage = 115V (+/- 5)

Frequency = 400 (+/- 20)

78
Q

Voltage splits into -

A

Line voltage - 200V (used for error checking )

Phase voltage - 115V

79
Q

P.D across phases

A

+ to + = 115V ( phase )

+ to - = 200V ( line to line )

80
Q

What separates the generator from the engine incase of failure ?

A

Disconnect unit ( dog clutch )
Located between Accessory gearbox and CSDU
Irreversible in flight.
Engine must be off to reconnect

81
Q

Potential generator failure indicators

A

High oil temperature and low oil pressure- monitored system.
If occurs Follow checklist !

82
Q

A well bonded airframe can be used as a common ….. for electrical circuits

A

Earth return

83
Q

If a resistor gets hotter ….
(Postive thermal coefficient)

A

Current reduces as resistance is increased

84
Q

What is the electrolyte in nickel cadmium batteries ?

A

Potassium hydroxide

85
Q

Ac generator (alternator) speed …?

A

Is constant RPM (CSDU)
Speed determines frequency (400Hz)

86
Q

What does High oli temp and low oil pressure lead too ?

A

Drive disconnect, which can’t be disconnected in flight ?

87
Q

How is generator controlled ?

A

GCU

88
Q

GCU functions

A

Everything apart from voltage regulation

89
Q

How is a rotating component connected to a non-rotating component in the generator ?

A

Slip rings and brushes

90
Q

How is initial excitation achieved in the AC brushless generator ?

A

A permanent magnet

91
Q

Inverter converts ?

A

DC to AC

92
Q

What does a TRU do ?

A

Convert AC to DC, usually to a lower voltage

93
Q

CDSU role ?

A

Drives the generator at a constant RPM to provide a constant 400 Hz frequency

94
Q

How is a spinning rotor connected to stationary parts of the generator ?

A

Slip rings and (carbon) brushes

95
Q

Issues with DC voltage regulator ?

A

bruh wear
losses due to friction

96
Q

How is excitation achieved in an AC brushless generator ?

A

A permanent magnet

97
Q

AC Generator paralleling increases ?

A

available current (same process as batteries)
separated by a paralleling breaker

98
Q

Rules for when a AC paralleling breaker closes ?

A

Voltage must be the exact same
frequency must be the exact same
phase must be within 90º
real load must match

99
Q

DC paralleling rules on breaker closure ?

A

Voltage must be the exact same (or risk of spark)
Load must match

100
Q

Rectification is ?

A

process of converting AC into DC
Very high efficiency
Diodes are used to control current flow

101
Q

What is a zener diode used for ?

A

Voltage stabilisation

102
Q

Purpose of battery cut out is ?

A

Stop DC alternator becoming a motor

103
Q

Hot bus is ?

A

connected directly to the battery and always live

104
Q

An inverter ?

A

Produces AC from a DC source
Is a solid state device- Has no moving parts

105
Q

TRU 2 functions ?

A

Transform voltage (reduce V 115- 24/29)
rectify current (AC to DC)
(It can only transform AC current)

106
Q

What TRU is most common on A/C ?

A

Step down transformer, achieved by swapping sides

107
Q

What can be said about the power across a TRU ?

A

Power in the TRU is equal on both sides, no loss or gain.

108
Q

GCB Is ?

A

generator control breaker
Makes the circuit online
Breaks the circuit so its offline

109
Q

Where is GCB ?

A

Between busbar and generator

110
Q

ECB is ?

A

Excitation control breaker (Normally closed)
ECB is closed when engine is off
Controlled by the GCU

111
Q

Potential fire issues ?

A

Electrics
Hydraulics
Fuel systems
Bleed air

112
Q

Major fault is ?

A

A rising fault
up to 120V
or
up to 420Hz

113
Q

What happens in event of major fault ?

A

ECB opens instantaneously and collapses the field, cutting off power immediately, this then shuts off whole AC assembly.

114
Q

In event of Major fault failure (Abv)

A

ECB opens
GCB opens
BTB closes

115
Q

BTB is ?

A

Bus tie breaker
controlled by corresponding side GCUs

116
Q

Minor fault ?

A

A falling fault
down to 110V
or
down to 380Hz

117
Q

In the event of a minor fault ?

A

GCB opens
BTB closes

118
Q

Differential fault is ?

A

A difference in measured parameters between a generator and bus bar

119
Q

Motor definition

A

Converts electrical energy into mechanical energy by generating mechanical rotor drive

120
Q

Generator definition ?

A

Converts mechanical energy into electrical energy

121
Q

Generator and motor relationship ?

A

Generator creates, motor receives

122
Q

How is the direction of rotation changed (DC motor) ?

A

Change/reverse polarity/direction of the applied current

123
Q

3 methods of connection in a practical DC motor ?

A

Series wound - (most utilised) - Torque
Parallel/shunt - Speed control (no torque)
Compound wound - Good mix of both

124
Q

Construction of a diode ?

A

A P-N junction
Positive type material - (one less electron)
Negative type material - (one extra electron)

125
Q

Diodes are very sensitive to what ?

A

Temperature, they will melt if they becomes too hot

126
Q

How are signal controlled ?

A

Logic gates ?

127
Q

AND gates ?

A

(D shaped with two lines entering flat side and one entering curved side)
TRUTH TABLE
A B Q
0 0 0
1 0 0
0 1 0
1 1 1

128
Q

OR gates ?

A

(Crescent shaped with lines going in either peak and out the curve centre)
TRUTH TABLE
A. B. Q.
1. 0. 1
0. 1. 1
1. 1. 1
0. 0. 0

129
Q

NOT Gate ?

A

Inversion gate, flips the signal
(Diode shaped but a ball at the end instead of a line, same entry and exit points)
TRUTH TABLE
A. Q
1. 0
0. 1

130
Q

NAND gate ?

A

(D shape but has a ball on outside curved surface, two entries on flat side and one through the ball)
TRUTH TABLE
A. B. Q
0. 0. 1
1. 0. 1
0. 1. 1
1. 1. 0

ATPL Theory (7 decks)

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