AGK Electrics Flashcards
What are static wicks?
- They dissipate static charge between the atmosphere and on aircraft in flight.
- Maintain 0V across fuselage.
- They’re attached to the trailing edges.
- Must have a certain number of static wick before flight -> if missing you must check if you have enough remaining before flight.
What is bonding? how does it protect?
Bonding sets the aircraft to be single/uniform potential by equalising the electrical potential throughout the aircraft.
- Protects against lightning effects
- Prevent radio interference
- Provide single earth return devices
- Bonding cable to prevent sparks
What is Kirchhoff’s first law?
Total current flowing into a point on a circuit is equal to the current flow out of that point.
What is a conductor? Give a material example
A conductor has free electorns
A conducting material is copper.
What is an insulator? Give a material example
An insulator has no free electrons
Examples of insulating material is glass, plastic, rubber.
What is a common earth system?
It’s where aircraft structures and bonding system is used to return to source I.e generator/battery.
Current is returned through a very low resistance path almost all voltage is used up.
What is a semi - conductor? Give example materials
Free electrons can be created.
Silicon
Germanium
What is static electricity?
The accumulation of electric charge of an object
What happens if generators fail?
if there is a battery remaining it should be used but it is time limited to 30 minutes.
What colour illuminates when driving gear is engaged? how long until the illuminate means there is a problem?
Amber light
If on more than 30 seconds after engine start, the starter motor must be disengaged, therefore, the the engine must be shut down.
What is magnetic field strength?
–A magnetic field can produce electric current
–A wire carrying electric current can produce a magnetic field (electromagnetic induction)
Outline Circuit breakers
Circuit Breakers are there to protect circuits. If one trips it has detected a fault (overload/overheat in the circuit).
If it is reset without first rectifying the fault then a risk of fire may exist.
Circuit breakers should not be used as a switch unless specified
e.g. as part of an emergency procedure drill to isolate parts of a circuit
Difference between AC alternators and DC generators
When generators were first invented, there were no diodes or semiconductors. The only option was to have a rotating armature (where the electricity is produced) and mechanically rectify the AC to DC using the Split Ring Commutator. The Field surrounded the armature in these devices and all the power had to come out from the rotating part, not good.
When diodes became cheap and were mass-produced, this meant that now the field could be rotated and fed with DC through some brushes and slip-rings, while the armature with all the generated power in it could be stationary. The AC produced in the armature was/is rectified using a bridge rectifier, which electronically converts AC to DC.
Very little current passes through the brushes to the field, and the rings aren’t split.
What is voltage control
The output of a generator is dependent on how fast it rotates and the size of the magnetic field inducing current into the armature.
Since overall resistance drops with increasing loads, we will need to reduce excitation with increasing RPM and increase excitation with increased load (more Amps being used in circuits).
If we don’t maintain the voltage constant, the circuits will have too much or not enough current and will fail to operate correctly.
Four batteries used in aircraft
Nickel-Cadmium
Lithium Polymer
Lead Acid
Lithium-Ion
