4.2 Electrical Systems Flashcards
What forms of electrical power are they?
3-Phase AC, AC, DC
Name types of Power Sources on an aircraft
Engine Driven AC Generators
Auxiliary Power Unit (APU) - power to start the engines, for backup
External Power - Ground power only, AC provided by a Ground Power Unit (GPU) through external plug
Ram Air Turbine (RAT) - emergency
Battery - backup or emergency power for typically 30mins, 28V DC and 1154AC (40Hz)
What electrical loads are on aircraft?
Motors and actuation, Lighting services, Heating services, Subsystem Controllers, Avionics Systems, Environmental Control System
Electrical Design Drivers:
total electrical load
power quality
safety
reliability
Electrical Design issues
Engine Power Off-takes
Generator and generator control
Power Switching
Wiring and Connectors
Whats the formula for the Engine Electrical Power Index?
EPI = Electrical Power / Number of Engines * Thrust/MTOW
in kW
EPI = Main Electrical Power per Engine * Thrust/Weight ratio
What backup systems for electrical Power are there?
Ram Air Turbine
Backup Generators and converters - variable frequency
Permanent Magnet Generators - used to generate 28V DC emergency power for high integrity systems (e.g. Flight control system)
What system configurations for power distribution exist?
Parallel Bus Systems - total electrical system load is shared on equally by all active generators in parallel
+ Generator load distribution
- High effort of controls (voltage, phase, frequency)
Split Bus Power Systems (standard)
each generator supplies power separately from the other generator
+ independent systrems
- more complex systems
Split Parallel bus systems ?
What are the primary functions of an electrical system?
Power generation
Power conversion and regulation
Power distribution and protection
What makes up the Constant frequency integrated drive generator?
the Integrated Drive Generator (idg) consists of a
Constant Speed Drive (CSD)
AC generator
How does the Generation Control Unit (GCU) work?
regulated the output voltage and provides portection
controls the Generator Control Breaker (GCB):
- GCB close: when all operation params are ok
- GCB open: when fault conditions prevail
monitoring and protection functions:
under/over voltage
under/over excitation
under/over frequency
differential current position
correct phase rotation
What conversion and chargers are there?
Inverters: VDC -> VAC single or three phase power
Transformer Recifier Units (TRUs): VAC -> 28VDC
Auto transformer units (ATUs): AC voltage -> another AC voltage
Auto transformer rectifier untis (ATRUs) - >conver unregulated VAC -> 270VDC power
Battery charger: like TRU, but dedicated unit for a controlled charge without overheating
What categories of wiring routes are there?
Non-customized routes: identical for all aircraft within family: power feeders and power distribution, flight control system
wiring segregated in differeing wiring routes -> important functions are not carried in the same routing,
redundant routes (flight critical routes are doubled)
Customized routes: customer/airline dependent routes for board electronics, galley systems, in flgiht entertainment
Whats a digital mock up?
A Digital Mock-Up (DMU) is a virtual computer-generated model of the aircraft which is being
used as the “master” reference for the entire development team:
* A highly detailed DMU helps to speed up development: Everyone can work as a virtual
team and shares the latest information during each phase of development/manufacturing.
* Beginning with the concept phase, the utilization of the DMU will extend throughout the
aircraft’s entire lifecycle (Airbus)
