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Ground School Systems 2 > Electrical Systems Introduction > Flashcards

Electrical Systems Introduction Flashcards

1
Q

What is the purpose of the Aircraft Electrical System?

A

Self contained network of components that generate, utilize, and store electrical energy.

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2
Q

What are the three building blocks that make up electrical atoms?

A
  • Negative charge is carried by the electrons
  • Positive charge is carried by the protons
  • Neutrons are neutral
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3
Q

When something has an electric charge, what does that mean?

A

Too few or too many electrons

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4
Q

How is voltage defined? Units?

A
  • Electric potential between two points per unit of charge
  • Considered the force that makes electricity move.
  • Volts (V)
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5
Q

What is current? Units?

A
  • Current is created when a conductive path is provided to facilitate movement of electrons in the form of an electrical charge.
  • Depends on supply voltage and resistance
  • Amps (A)
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6
Q

What does Watts mean?

A
  • Rate of energy transfer within an electrical system

- Product of V and A

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7
Q

What is resistance? What are some factors that affect it?

A
  • Measurement of the opposition present to the electrical current flow.
  • The lower the resistance the greater the current flow, reducing amount of supply required and size and weight of componentry involved.
  • Wire diameter, wire material
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8
Q

What materials are good conductors?

A

Metals

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9
Q

What materials are bad conductors?

A

Plastic, wood

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10
Q

What occurs to the resistance as a conductor heats up? What about when an insulator heats up?

A
  • For conductor, resistance increases.

- For insulator, resistance decreases.

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11
Q

What is Ohms law? What’s the mathematical equation?

A
  • The electrical current in a circuit or conductor will always be proportionate to the voltage across the conductor or circuit and inversely proportional to the total resistance.
  • V = IR
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12
Q

What is Earth/Ground?

A
  • Reference point in an electrical circuit from which voltages are measured
  • Used to facilitate protective mechanism should a fault in the system require that power be removed immediately from that circuit.
  • This ensures that exposed components never have a dangerous voltage with respect to ground, therefore eliminating the risk of an electrical shock should a “grounded” person touch them.
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13
Q

What is a closed circuit?

A

Complete electrical circuit through which current can flow.

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14
Q

What is an open circuit?

A
  • A state where there is no complete path for current to flow within a circuit.
  • Can be by design through components such as switches
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15
Q

What is a short circuit?

A

When resistance becomes lower, resulting in an excessive flow of current, excessive heat and failure of components.

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16
Q

What is a generator? How does it work?

A
  • Device that can generate either AC or DC electricity.

- Through electromagnetic induction, converting mechanical energy into electrical energy.

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17
Q

How does electromagnetic induction work?

A
  • Moving a magnetic field field in relationship to a conductor.
  • Either conductor or magnet can be moving or stationary.
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18
Q

What will occur in a generator?

A

A coil of wire is moved through the magnetic field of a powerful electromagnet, producing a large voltage.

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19
Q

What is the value of the induced voltage dependent on?

A
  1. Number of turns in the conductor coil
  2. Strength of the electromagnet
  3. Speed of rotation of the conductor or magnet
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20
Q

What is alternating current?

A

Electrical current that periodically reverses direction.

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21
Q

What does a AC generator consist of?

A

A rectangular coil of wire which can be rotated about an axis.

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22
Q

What is required for current to flow ?

A

Generator is electrically connected to an external circuit with an electrical load.

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23
Q

What is single and three phase power?

A
  • AC generators produce single-phase AC power are less common, as three-phase AC generators are more efficient
  • The three-phase supply is able to be used by aircraft equipment designed for single-phase power as well as three-phase power.
  • Three phase power has three separate coils of windings 120 degrees apart. Single-phase AC is induced into each coil
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24
Q

What is Direct Current (DC)?

A

Unidirectional flow of an electric charge

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25
Q

What is the simplest DC generator?

A

Created by taking the single-loop AC Generator describe previously and replacing the slip rings with two half-cylinders.

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26
Q

In a circuit, which way does electricity flow?

A

Positive to negative

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27
Q

What is the point at which current enters an electrical circuit called?

A

Source or supply

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28
Q

What is the point at which current leaves the electrical circuit called?

A

Return or earth.

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29
Q

What are loads in a circuits?

A

Components in the circuit that required power.

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30
Q

What type of applications is AC power used for? What about DC?

A
  • Powering large appliances/loads

- DC is used for less intense operations such as control circuits and electronics

31
Q

How is resistance determined in a series circuit?

A

RT = R1 + R2 + R3 …

32
Q

How is resistance determined in a parallel circuit?

A

1/RT = 1/R1 + 1/R2 + 1/R3 …

33
Q

What is insulation?

A

Material which limits or prohibits current flow

34
Q

What is a resistor?

A
  • Passive electrical component used to induce an electrical resistance.
  • Used to regulate current flow, adjust signal levels, divide voltages, and bias current pathways.
35
Q

What is a capacitor?

A
  • Used to store electrical energy within a circuit

- Eliminate DC but allow AC to pass.

36
Q

What is a transistor?

A

A semiconductor control device used to amplify or switch electronic signals or electrical power.

37
Q

What is a transformer?

A
  • A device that can be used to change both the voltage and the current of an AC power source (higher or lower).
38
Q

What is a rectifier ?

A
  • A device used to alter current from AC to DC, with the power and voltage levels remaining constant.
39
Q

What is a transformer rectifier units (TRU)?

A

Performs a combination of transformer and rectifier functions provided above

40
Q

What is an inverter?

A

Used to alter current from DC to AC.

41
Q

What is a fuse?

A

Used to facilitate overcurrent protection for an electrical circuit.

42
Q

What is circuit breaker?

A
  • Circuit breaks is an automatically-operate switch design to protect the circuit from damage due to excessive current conditions.
  • Designed to be reset by manual or automatic means.
43
Q

What provides electrical power in normal operation of an aircraft?

A
  • Engine-driven generators that provide electrical power

- Auxiliary power units (APU) or batteries that provide electrical power when the engines are not running.

44
Q

How does a basic electrical system operate?

A
  • Electrical power is supplied by either batteries, APU or onboard power generation to a busbar
  • The busbar distributes this electrical power to the reliant systems
  • The current then flows through a return wire attached to the aircraft metal structure to complete the circuit
45
Q

What electrical power systems do modern military aircraft use?

A
  • 24V DC (rated at 28V to enable 24V charging of batteries)

- 115 VAC, 500 Hz, 3-phase generator system

46
Q

Which system do aircraft with low electrical demands usually operate on?

A

DC-based electrical system

47
Q

Which system do aircraft with high electrical demands usually operate on?

A

AC-based system.

48
Q

What are some electrical power sources that are commonly used?

A
  • Batteries
  • Onboard generators
  • Converted electrical power
  • Auxiliary electrical power
  • Emergency electrical power
49
Q

What is a battery? What are the two types?

A
  • Battery is a device that stores energy in chemical form

- Two type are: Primary + Secondary

50
Q

What is a primary cell?

A

Only allow DC power

51
Q

What is a secondary cell?

A

Allow both charging and discharging of DC power.

52
Q

What is the capacity of a battery?

A

How much current the battery can provide for a specified time.

53
Q

What is a Transformer Rectifier Unit (TRU) used for?

A
  • A combination of a static transformer, a rectifier and a DC electrical filter.
  • Used to convert 115 V AC input to 28 V DC.
54
Q

What are inverters used for? What are the two types?

A
  • Rotary inverter
  • Static inverter
  • Converts DC into AC
55
Q

Which two systems can provide auxiliary electrical power?

A
  • Ground Power Unit (GPU)

- Auxiliary Power Unit (APU)

56
Q

What are GPU’s used for?

A
  • Aircraft maintenance and servicing.

- Aircraft systems and engine starting

57
Q

What are Auxiliary Power Units (APU)?

A
  • Capable of providing both electrical and pneumatic power for aircraft starting.
  • Provides flexibility for the aircraft to operate in most locations
58
Q

For aircraft with a DC electrical system, what can be used to power vital electrical systems for a short period of time?

A

Main battery or emergency battery

59
Q

For aircraft with a AC electrical system, what can be used to power vital electrical systems for a short period of time?

A
  • Standby generator driven by:
    • Ram air turbine (RAT)
    • the APU
    • Pneumatic or hydraulic systems
60
Q

What is a ram air turbine?

A

Turbine that is put into inlet or slipstream to turn a generator to create electricity.

61
Q

What is a busbar?

A

Main conductor and distribution centre in the electrical system

62
Q

What is the principle of a split busbar?

A

To divide all electrical services into three categories of importance which allows for manual or automatic isolation of less important systems in the event of an emergency.

63
Q

What are the three categories of importance with regards to electrical services?

A

1) Vital Services - services required during an emergency
2) Essential services - services that are required to ensure safe flight during in-flight emergencies
3) Non-essential services
- services not essential during flight

64
Q

What is a single channel DC system?

A
  • All essential and non-essential services are fed by a single busbar.
  • Streamlined electrics to reduce workload of pilot
65
Q

What is twin channel split busbar DC system?

A
  • Same theoretically as the single channel system but is generally used where there are two generators
  • Only different is that non-essential DC services are not powered when only batteries are available for power.
66
Q

What does the voltage regulator do?

A

Regulates the voltage to ensure it does not get too large/small

67
Q

What provides frequency regulation for AC current?

A
  • Constant Speed Drive Unit (CSDU)

- Works to regulate the speed of rotation of the generator which determines the frequency of the AC current.

68
Q

What is normally provided as redundancy if the CSDU fails?

A

Protection Unit

69
Q

What two components are used to control various A/C systems?

A
  1. Switches

2 Relays

70
Q

What are electrical switches used for?

A

To complete or interrupt an electrical circuit

71
Q

What are relays?

A

Remotely controlled electrical devices used to switch one or more circuits

72
Q

What are some protection devices used?

A
  1. Fuse
  2. Circuit breakers
  3. Reverse Current Cut-Out (RCCO) sensors
73
Q

In a DC generator, which component ensures the external current in the load only flows one way?

A

Commutator

74
Q

What is the purpose of a Reverse Current Cut Out (RCCO)?

A

Disconnect a generator from a busbar if the generator’s voltage falls below that of the busbar.

Ground School Systems 2 (19 decks)

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