Electrics Flashcards
Electric system.
28V DC system
Power Generation (PG) Describe the generators
Two 60A alternators
mounters bottom left of each engine
driven by a flat belt
PG - What happens when the alternators are off?
Power is provided by the main battery
PG - What is the L/R power output line connected to?
The LH/RH main bus via LH/RH alternator relay and a 70A circuit breaker
PG - What are the main buses connected to?
The Battery Bus via a 90A circuit breaker
PG - Purpose of generator output lines?
Generator output lines run through current sensor for each alternator
-> Which provides power supplied to electric system by an alternator. Including battery charging
PG - What happens when the main battery fail?
The field of each alternator is energised by two 12V 1.3Ah sealed lead acid batteries (excitation batteries) connected in series - installed in baggage nose compartment
PG - When are the Back up batteries used?
When the main battery and alternators fail. The two separate 24V 1.3Ah Back up batteries power each ECU
PG - What do the LH/RH engine master connect?
They connect the excitation battery to alternator field via a 5A fuse
PG - Why does each alternator have a control unit?
To measure alternator output voltage,
Controls current through alternator field coil via a pulse-width modulated signal.
-> so field signal modulated to keep output voltage stable in all load and speed situations
Storage (S) - Main battery storage?
24V 10Ah lead acid battery
S - What is the Main battery connected to?
The Hot battery bus and Battery bus via the battery relay - installed in relay junction box
S - What controls the battery relay?
The Electric master
S - What is the Non-rechargeable dry battery for?
A source for the artificial horizon and flood light
S - When is the Non-rechargeable dry battery used?
When the emergency switch is on, the artificial horizon and flood light supplied with power for 1.5hrs.
S - How many times can you use the Non-rechargeable dry battery be used?
Once. Has to be replaced after use or every 2years.
Distribution (D) - What distributes power?
Hot Battery bus, Battery bus, LH/RH ECU Bus, LH/RH Main bus and Avionic Bus
D - What does the Hot battery bus connect to?
To the Main battery
D - Key things about the Battery bus.
Connected to main battery
Via Battery relay
Controlled by Electric master
D - Key things about the ECU Bus.
Connected to LH/RH main bus via a diode
Connected to power output line of the alternator via a diode and 30A circuit breaker
D - How long does ECU Backup battery provide power for?
30 mins if there’s a complete electrical failure.
D - What does a Main bus connect to?
A battery bus via a 90A circuit breaker
D - What to the LH and RH Main bus power?
LH Main bus - consumers
RH Main bus - Avionics bus via Avionic master relay
Consumer connections
Consumers connected to appropriate bus via automatic circuit breakers.
Voltage min and max
Min - 24.1V
Max - 32.0V
Amperage max
Max - 60A
