11.6 - Electrical Power Flashcards
What happens when the disconnect solenoid is energised while the engine is stopped
The disconnect device is triggered and the clutch is damaged when the engine is started
How is a CSD disconnect reset performed
The reset ring is pulled when the engine is completely stopped
What is the function of the voltage regulator in the GCU
To control the voltage at the point of regulation 115V by influencing the ecciter current
Which is the voltage for an under voltage condition
100 volts
What happens with a generator working in isolated condition when it receives more exciter current than necessary
Voltage will increase
When does the differential protection circuit trip the generator
When the current in 1 phase differs
What happens when you exchange 2 phase connections at the generators terminals
The generator runs in reverse
How can you check the charge level of a ni-cad battery
You must measure the charge current, if it is nearly zero the battery is fully charged
What happens when a ni-cad battery overheats during charging
The charging current increases and could/would start a thermal runaway
Which of the following methods is used to charge a battery in an electrical power system
The batteries can be charged by a Transformer Rectifier Unit (TRU) using the constant voltage charging method
Consider a 2 engine aircraft with a isolated orientation of the main bus bar, what happens in the event of a failure of one of the main engine generators in flight
The remaining engine generator supplies the main AC bus bar on the failed side via the bus-tie breakers and the galley loads are shed
Consider a multi-engined aircraft (x4) with parallel generators. What happens if the number 2 bus-tie contactor is opened
Generator 1, 3 and 4 supply main bus bar 1, 3 and 4 in parallel and generator 2 powers main bus 2 seperatly
How is an open phase in a generator detected
By comparing the generator load in each phase
What does it mean when a Avail light in the external power push button illuminates
The external power source is activated to supply the network and the GND service must be switched to
How are the engine driven generators of multi engined aircraft (3 or 4 engines) usually operated
In parallel operation
How many resets are permitted after a circuit breaker has tripped
1, to prevent contacts from welding if a short has occurred
What does the abbreviation RCCB mean
Remote Control Circuit Breaker
Which is the principle of operation of the CSD disconnect
Electronically disconnected and mechanically reconnected
Which is the maximum permitted time for operating a CSD disconnect button
3 seconds
Which protective functions are built into the aircraft’s transformer rectifier (TR) units
Low current and high temperature protection
Why are there 2 short pins in there external power receptacle
They ensure that the external power can only be applied if the plug is located correctly in the power receptacle
How can the CSD disconnect be reliably confirmed
Zero volts and zero frequency is indicated
Which are the main components of a static inverter
Solid state switches and a transformer
What happens if the bus tie switching is set to off during operation with only ground power available
Te power to the main bus bar is lost
What is the main advantage of parallel operation of the main AC busses over isolated operation
All engine driven generators are loaded equally and there is no power loss when one generator fails
Why are trip free circuit breakers used on aircraft
Because they can open an overloaded circuit even with the control knob jammed in
Which statement accurately describes the bus-tie switching operation in a Boeing multi engined aircraft
The bus-tie switching is normally closed. This is known as parallel operation
Consider the function of a GCU. Which of the following statements are true
The GCU’sof the engine driven generators are identical and interchangeable
How are the engine driven generators of a twin engine aircraft usually operated
In isolated operation
What is the purpose of the 2 min delay before resetting a circuit breaker
To allow the bi-metallic strip in the circuit breaker to cool down
Which statement is correct concerning the input speed of the generators producing a voltage with a frequency of 400Hz
The speed depends on the amount of pole pairs, 24000 RPM with one pole pair and 8000 RPM with three pole pairs
How does the static inverter generate the correct output frequency
With a beat generator
Which statement is correct concerning the functions of a circuit breaker
The CB trips when the normal current is exceeded for a certain time even if the control knob is pressed
What is the Transformer Rectifier Unit (TRU) used to convert
3 phase 115V AC from the AC power distribution into 28V DC for the DC power distribution
On a 3 phase generator what is the angle between phases
120deg
What electrolyte solution is used in a Ni-Cd battery
A strong alkaline
What is the voltage and frequency required to energise the aircraft electrical system
115V AC and 400Hz
How is the aircraft normally electrically powered in flight
Engine driven generators
What is the main source of power when the Aircraft is on the ground
External power
How is the speed of the motor controlled in the CSD
Hydraulically
Which are the main components of a static inverter
Solid state switches and a transformer
What is the function of the GCU regulation circuits in generators that can work in parallel
To make sure that all generators share the same load when they are switched into parallel operation
What is the function of the voltage regulator in the GCU
To control the voltage at the point of regulation to 115V by influencing the exciter current
What is the main advantage of parallel operation of main AC buses over isolated operation
All engine driven generators are loaded equally and there is no power loss when one generator fails
Which of the following power source can work in parallel operation
APU and external power
Which statement accurately describes the bus tie switching operation in a Multi engine aircraft
The bus tie switching is normally closed. This is known as an isolated operation
Which is the maximum current value that can be used in aircraft circuit breakers
125 amperes
Which of these protection functions is used in TR units
Over temperature protection
Which statement is correct concerning the function of a circuit breaker (CB)
A CB trips when the nominal current is exceeded for a certain time, even if the knob is pressed
