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Powerplant > Engine Electrical Systems > Flashcards

Engine Electrical Systems Flashcards

1
Q

What is a generator?

A

A machine that changes mechanical energy into electrical energy

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2
Q

By what means does a generator produce electricity?

A

Electromagnetic induction

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3
Q

What are 3 ways to change the value of induced voltage?

A

-Number of magnetic lines of flux (windings)
-Change the rate of movement (speed)
-Number of conductors affected (strength)

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4
Q

What is a commutator?

A

A mechanical switch, or rectifier, that converts the AC generated within the armature of a DC generator into DC as it leaves the generator.

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5
Q

What is the commutator made of?

A

Copper

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6
Q

What is commutation?

A

The system of changing the AC of the armature to DC in the external circuit

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7
Q

How can residual magnetism be restored?

A

By passing DC from a battery thru the field windings in normal direction of current flow

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8
Q

What is the procedure for restoring residual magnetism known as?

A

Flashing the Field

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9
Q

What is residual voltage?

A

A result of residual magnetism in the field poles

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10
Q

Aircraft generator output is normally rated in what?

A

Volt/Amps

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11
Q

The maximum allowable voltage drop between the generator and the bus bar is:

A

2% of the regulated voltage of the generator

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12
Q

How are generators classified?

A

Depending on how the field coils are connected to the armature

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13
Q

What are the 3 classifications of DC generators?

A

Series Wound
Shunt Wound (most common)
Compound Wound

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14
Q

In a series wound generator, what causes the voltage to increase and decrease?

A

When the load is increased, the voltage increases
When the load is decreased, the voltage decreases

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15
Q

In a shunt wound generator, what is required?

A

Must always be used with a voltage regulator

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16
Q

How do you eliminate armature reaction?

A

-Shifting the position of the brushes
-Interpoles
-Compensating windings

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17
Q

What is the best method for eliminating armature reaction?

A

Interpoles used with compensating windings

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18
Q

True or False? Compensating windings can be used alone.

A

FALSE
They are used to increase the interpoles effectiveness

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19
Q

What are the 5 main components of a DC generator?

A

-Armature assembly
-Field frame assembly
-Brush assembly
-End frames
-Cooling fans/ducts

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20
Q

What is the commutator made up of?

A

Copper segments insulated with Mica

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21
Q

How much should the mica insulation be undercut?

A

0.020 in. Or equal to the width of the mica

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22
Q

What causes arcing and bouncing of the brushes?

A

Weak spring tension

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23
Q

What causes excessive wear to the commutator and/or brushes?

A

Heavy spring tension

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24
Q

What are the 3 cooling methods for a DC generator?

A

-Fan
-RAM air
-Compressor bleed air

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25
Q

What is paralleling?

A

Electrically balancing the current load among the generators in a given system

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26
Q

Generator loads should be within ____ of each other.

A

+/- 10%

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27
Q

When are starter brushes supposed to be replaced?

A

When they are worn to about 1/2 of their original length

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28
Q

How can you fix a commutator that is rough or pitted?

A

With NO. 000 Sandpaper

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29
Q

How can you seat the starter brushes?

A

Use NO. 000 Sandpaper
OR
Abrasive stick

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30
Q

What do the brushes connect to?

A

Pigtails
(Pigtails connect to rivet)

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31
Q

What does FAR 23.1351.d state?

A

A voltmeter and/or ammeter is required to measure electrical power system quantities

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32
Q

Electrical load should not exceed _____ of the generator capacity.

A

80%
(If greater, it must have a warning placard or monitoring device)

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33
Q

What is an ammeter referred to as?

A

A Loadmeter

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34
Q

What does the Loadmeter(ammeter) show when placed in the generator output?

A

Only the charging of the battery

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35
Q

What does the Loadmeter(ammeter) show when connected at the battery?

A

Shows both charging and discharging of the battery

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36
Q

True or False?
A voltmeter should indicate output of the generator to be higher than battery voltage.

A

TRUE
14v for 12v system
28v for 24v system

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37
Q

What is the only practical way to regulate the generator voltage?

A

Vary the strength of the field

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38
Q

The voltage regulator controls the amount of current flowing to the field coils through the use of a ________ or _________ resistor.

A

Variable
Or
Intermittent

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39
Q

What are the 3 types of voltage regulators?

A

-Carbon Pile
-Vibrator
-Solid State

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40
Q

How is resistance adjusted with a carbon pile regulator?

A

Spring Pressure
More compression = Low Resistance
Less compression = Increased Resistance

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41
Q

The vibrator regulator has points that open and close to adjust the voltage. What designates how long the points will remain open?

A

The Load

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42
Q

What is the most common type of voltage regulator used on light aircraft?

A

Solid State

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43
Q

What are the 3 Unit Control Systems?

A

-Voltage Regulator
-Current Limiter
-Reverse Current Cutout Relay

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44
Q

What does the current limiter do?

A

Reduces the generator voltage whenever the maximum safe current load is exceeded

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45
Q

What unit is designed to protect the generator from current loads that will cause it to overheat and eventually burn the insulation and windings?

A

Current Limiter

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46
Q

What is the reverse current cutout relay?

A

An automatic means to disconnect the generator from the battery when the generator voltage is lower than battery voltage

(Water runs down the hill)

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47
Q

What is an advantage of the starter generator?

A

Reduction in both size and weight

48
Q

What is a disadvantage of the starter generator?

A

Unable to maintain full output at low RPM and therefore is only used on turbine aircraft that sustain a high RPM

49
Q

What are the 2 types of alternators?

A

AC & DC

50
Q

What alternator is used most often on light aircraft with a small electrical load?

A

DC

51
Q

What are 3 advantages of AC?

A

-Voltage and current can easily be stepped up or down
-Power may be supplied at a high voltage with low current
-Low current allows the use of small gauge wires which saves weight

52
Q

What are the differences between alternators and generators?

A

Generator
Rotating armature
Stationary field
Alternator
Stationary armature
Rotating field

53
Q

How many phases are produced in an alternator?

A

3 phase

54
Q

In an alternator, the stator has _____ separate windings that are ______ degrees apart.

A

3 separate windings
120 degrees apart

55
Q

What are the 3 main components of an alternator?

A

-Three-phase stator (armature windings)
-Rotor (field windings)
-Rectifier assembly

56
Q

How are alternator rotor windings excited?

A

By DC from the aircraft battery, through the voltage regulator

57
Q

What is motoring?

A

When the battery is discharging through the generator

58
Q

What DC motor has the highest starting torque of any other type of electric motor?

A

Series Wound

59
Q

How many diodes are connected to form the three-phase, full-wave rectifier?

A

6

60
Q

What does the 6 diode rectifier assembly do?

A

Converts all three phases of AC to DC

61
Q

What do rectifiers in the form of semiconductor diodes do?

A

Prevents reverse current flow from the battery in the event the alternators output voltage is less than battery voltage

62
Q

What allows the alternator to produce more power at a lower RPM than a generator?

A

It has multiple (8 or 12) poles alternately spaced with north and south polarity so it has more and stronger field poles

63
Q

How are alternators driven?

A

-Belt & pulley
Or
-Gear-driven & flange mounted

64
Q

What are AC generators rated in?

A

Volt/Amps

65
Q

What frequency do almost all AC powered aircraft electrical systems utilize?

A

400 Hertz

66
Q

What do AC power systems require to maintain a constant speed?

A

A Constant Speed Drive (CSD)

67
Q

What is the equation for determining frequency?

A

Number of poles RPM
————————- X ————-
2 60

68
Q

What is the equation for determining speed?

A

Frequency x 120
——————————-
Number of poles

69
Q

What are the 5 classifications of AC generators?

A

-Voltage
-Amperage
-Phase
-Power Output
-Power Factor

70
Q

What are the 3 ways of maintaining constant speed or frequency?

A

CSD
IDG
VSCF

71
Q

What device is used for converting DC into AC at the frequency and voltage required?

A

Inverter

72
Q

What are the 2 different types of inverters?

A

Rotary & Static

73
Q

What is the most common inverter?

A

Static inverter
Also known as Solid-State type

74
Q

Wires must only be specifically designed for aircraft use. What type is normally used?

A

Stranded

75
Q

When copper wire is replaced with aluminum wire, the aluminum wire should be:

A

Two sizes larger than the copper wire size
(Aluminum wire has more resistance)

76
Q

What size wire should not be used on aircraft?

A

AWG size 8

77
Q

What is the minimum bending radius for wires?

A

Single wire is 3x the wire diameter
Preferred is 6x diameter

78
Q

What must be done to prevent excessive stress on wire insulation when installing wire bundles?

A

Wire bundles must not be less than 10 times the diameter of the largest wire or cable in the bundle

79
Q

When is double cord lacing used?

A

On wire bundles of 1 inch diameter or larger

80
Q

Maintain a minimum clearance of _______ from any control cable.

A

1/2 inch

81
Q

True or False? Wires should be routed below fluid lines.

A

FALSE
Wire should be routed above or on a level with fluid lines and maintain a 6 in separation

82
Q

If separation from flammable fluid lines is impractical, run the electrical wire a minimum of _______ above the flammable fluid line and secure.

A

6 in

83
Q

Wire bundles should be limited in size to:

A

75 wires or appx 2” diameter

84
Q

What are the 3 types of connecting devices?

A

-Quick disconnect (AN/MS)
-Crimp type
-Solder

85
Q

Describe a quick disconnect connector.

A

Wires are put inside an insulated plug with pins and sockets that mate with the opposite type of terminal

86
Q

On a quick disconnect connector, sockets are ______ and Pins are _______.

A

Sockets are Positive +
Pins are Negative -

87
Q

How are crimped terminals designated?

A

According to wire size and size of the terminal stud

88
Q

What are the terminal insulation colors and sizes?

A

YELLOW: 10 - 12 AWG
BLUE: 14 - 16 AWG
RED: 18 - 20 -22 AWG

89
Q

What is the most common crimp type terminal?

A

Ring type

90
Q

If several splices are to be made in any wire bundle, splices should be:

A

Staggered to reduce bundle diameter

91
Q

How many terminals are permitted to be on a terminal strip?

A

4

92
Q

What are 2 things to ensure when dealing with bonding straps?

A

-Make as short as practical
-Resistance of each connection cannot exceed 0.003 ohms

93
Q

Where should circuit breakers be located?

A

As close to the power source as possible

94
Q

What is a conduit designed to provide?

A

Mechanical protection

95
Q

What can conduits be made of?

A

Metallic or non-metallic
Aluminum
Brass
Fiberglass
Rigid or flexible

96
Q

What size should a conduit be?

A

25% larger than maximum bundle size

97
Q

What is used to lubricate the inside of an electrical conduit to aid electrical wires being pulled through?

A

Soapstone Talc

98
Q

What are the 3 high current surge circuits?

A

-Incandescent Lamps
-Electric Motor
-Inductive Circuits

99
Q

What is Derating Factor?

A

A multiplier that is applied to determine the capacity of a switch for a particular installation

100
Q

How do you find the Derating Factor?

A

It will be listed in a chart or given to be calculated with Amps x DF

101
Q

How should switches be installed?

A

Should always be installed so the lever will be moved up or forward for ON and down or aft for OFF

102
Q

Electromagnetic Switches are usually called:

A

-Relays
&
-Solenoids

103
Q

What is the difference between a relay & a solenoid?

A

Relay = electromagnetically operated movable contact switch
Solenoid = electromagnetically operated moveable core switch

104
Q

What are the two duty cycles that solenoids and relays may be designated by?

A

-Continuous (> 2 Min)
-Intermittent (< 2Min)

105
Q

What are 3 circuit protection devices?

A

-Fuses
-Current limiters
-Circuit breakers

106
Q

What are the 2 variable resistors?

A

Rheostats
&
Potentiometers

107
Q

Describe 4 things about Rheostats:

A

Connects in series
Varies CURRENT
Low resistance
Has 2 terminals

108
Q

Describe 4 things about Potentiometers:

A

Connected in parallel
Varies VOLTAGE
High resistance
Has 3 terminals

109
Q

Capacitance depends on what?

A

-Area of the plates
-Dielectric thickness
-Dielectric material

110
Q

What are 2 types of capacitors?

A

Fixed & Variable

111
Q

What are the 5 types of materials that can be used as insulation inside capacitors?

A

-Paper
-Oil
-Mica
-Electrolytic
-Ceramic

112
Q

What is a transformer?

A

A device used to increase or decrease the voltage in an AC circuit.
Allows for high voltage with low power loss.

113
Q

What is inside of a transformer?

A

A primary winding and a secondary winding on a laminated soft iron core.

114
Q

What is the purpose of a laminated core?

A

Reduces the effects of eddy currents

115
Q

How many diodes are used in a 3 phase rectifier?

A

6

Powerplant (13 decks)

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