11.6 Flashcards
Ac and dc voltages
Ac 115
Dc 28 -> 24
In a 3 phase system what’s the voltage between each phase
120
How long is emergency power from the battery for
At least 30m
What is the battery used for
Emergency power and apu start
What power source does the EDG provide during flight
Dc power source
Why do we need vents on batteries
Gas to escape and prevent spillage
How can you disconnect the battery in an emergency
By hand no need for wire cutters
Cell voltage when discharged and charging
1v when discharged
1.5v when charging
How often does maintenance occur on batteries
Every 2000 hours but never performed on aircraft
Why is it necessary to avoid too many apu starts
Overheat the battery which reduces electrolyte level and melts plastic separator
What voltage should you not discharge a battery
Under 22v
What should you monitor on ni cad batteries
The voltage and current during charging
What battery is constant voltage
Lead acid
What battery is constant current
Ni cad
When removing a battery what do you disconnect first and why
Negative lead to prevent shorts
What is lead acid electrotype topped up with
Distilled water only
What are the characteristics of lithium ion batteries
8 cells
28dc
75amph
What’s the advantages of lithium ion batteries
30% lighter
Quicker recharge
No memory degradation
Lithium ion charging stage
Constant current
Balence
Voltage source
Source of power for DC
Battery
External
Generators
How does the generator state the direction of rotation
On the identity plate or an arrow on the stator externally
What does a tru do
Turn ac into dc voltage at 28v or 14v
How does the parallel system work
Two or more generators connected to the sync bus
How does non-parallel work
All the loads are supplied through the bus bar
What does an equalising coil do
Makes sure the power supplied or consumed by the IDG is equal
What happens if one of the generators fails and bus tie breaker closes
The two bus bars connect with serviceable generator to supply both busbars
What 3 things generate ac current
Ac generators
Static inverters
Rotory inverters
What phase is ac generation
Three phase 400hz
115/200v
How is generator output controlled in ac
Integrated control and protection unit
What is AC wild
Faster the rotor turns, the higher the frequency
What does a csd do
Adapts variable engine speed into constant
What’s the purpose of fly weights
Keeps output at 400hz
What’s the oil circuit used for
Cooling and lubrication
What does a generator rotor do
Increase or decrease voltage of frequency outlet
What the two temperature indications
Absolute oil temperature and rise in temperature
What is underspeed
Input speed drops below normal control range
What a constant speed drive disconnect
Electrically actuated device that decouples the input shaft from the input spline shaft if futures transmission malfunction
How do you know if the csd disconnection is successful
Voltage and frequency will display 0
How do you operate the disconnect button
Press no longer then 3 seconds
Don’t press more then once every 60 seconds
How does the constant speed drive unit work
Concert variable engine rpm to generator speed of 12000 rpm
What type of generator is csdu and what does it output
Brushless
200v at 400hz and also 90kva continuously
What are the 3 gcu functions
Regulation
Protection
Switching
What is a current transformer
Used as an amp clamp
Is there physical contact between cables and the transformer
No
How is emergency power generated
Battery and ram air turbine
What bus is the battery connected to
Hot battery bus
What is the essential bus connected to
Anything that will allow the aircraft to fly safe
What is voltage regulation done by
Gcu
How are the poles ordered
Always in pairs
How are poles ordered in DC
2,4,6 poles
What is an inverter
Dc to ac
28vdc becomes 26vac or 115vac
What inverter is better
Static as it quieter and has no moving parts
What does a transformer do
Steps voltage and current up & down
Current and voltage work in opposite
What are rectifiers and the 2 types
Change ac to dc
Half wave & full wave
What does a tru do
Convert 115vac from engine or apu to 28vdc
What is main power distribution
Electrical power to main consumers
Who is the emergency power distribution for
Consumers that can land aircraft safely
What are fuse and circuit breakers used to do
Prevent currents Higher then the maximum of the cross sectional area
What do you do with a blown fuse
Replace after blown
What do you when a circuit breaker pops
Reset after the circuit fault is removed
How many times can you replace a circuit breaker in flight
Once
Why are circuit breakers used as manual on/off switches
To allow deviation of circuits
What is a short circuit
Hard short between high voltage side to ground or different potential difference
What type of cb is push/pull pop out
Single-pole thermal device
What is the most common circuit breaker
Thermal & magnetic or electromagnetic
What voltage does an external ground power unit supply
115vac and 28vdc
How many pins in dc got
3 pins
2 positive
1 negative
How many pins does an ac gpu have
6 pins
4 larger ones
2 smaller
In an AC gpu what are the 4 pins
Phase A B C & nuetral
