Study Guide Electrical Flashcards
What happens if a power generating source fails?
Bus ties automatically connect to provide no system degradation.
What components power the AC system?
Two integrated Drive Gemerators APU Inverter Ram air turbine AC GPU receptacle
What components power the DC system?
2 NiCad batteries
Three transformer rectifier units
DC GPU receptacle
How does the IDG maintain a stable power output?
A constant speed drive that attaches the IDG to the AGB,,,, accessory gear box…… This converts variable engine speed into a constant rpm.
What monitors and controls the IDGs?
Each generator has a GCU,,, generator control unit.
Can one IDG supply the entire electrical system?
Absosmurfly
What will cause the a,her IDG light on the overhead panel to illuminate?
High oil temp and low oil pressure.
If an IDG is manually disconnected can pilots reconnect it?
No, mx function
What is the primary function of the AC generators?
To power the AC busses and AC ESS bus, which power the three transformer rectifier units.
What is the function of the TRUs?
To convert 115 volt AC to 28 volt DC.
How is it known that an AC GPU is hooked up to the plane and ready to provide power?
GPU button will have avail light and the GPU icon will show on the electrical page. Once it is pushed in the will show in use provided another source of AC power is not available.
What does it mean if the GPU is plugged in and the outside panel says IN USE?
Ground service bus is in use.
Flight deck will still show AVAIL and can be used.
What charges the batteries?
Any AC power source.
How long will the batteries last without recharging?
Ten minutes
What is the purpose of the DC GPU receptacle?
For APU start when batteries are less than 22.5 volts or if battery temp is less than -20 degrees C
What is the minimum battery voltage to close the battery bus ties?
18 volts
What battery is used for APU start?
Battery two is used for the start and battery one is powers the FADEC and EICAS.
What is the purpose of the inverter?
Converts 28 volt DC for the batteries to 115 volt AC to power the AC standby bus when an AC power source is not available.
What is on the AC standby bus?
Engine exciters 1a and 2a
What powers the ram air turbine?
Airflow
When will the RAT deploy?
Total loss of AC power or when manually deployed by the pilots.
How long after deployment will the rat supply AC power?
Eight seconds
With total loss of AC power and rat does not deploy within eight seconds is there a total loss of power?
No, batteries supply power to the DC ESS busses and the AC standby bus via the inverter.
What does the rat power?
ESS busses
What is the min airspeed for the rat?
130 knots then it starts to load shed.
What manages the electrical system?
Four ICC s…..integrated control centers
Two secondary power distribution assemblies SPDA
What is an ICC?
An electrical control device which provides power distribution and protection for electrical loads.
What is an SPDA?
An electrical load management unit which is powered by the ICCs and distributes electrical loads to aircraft systems according to distribution logic.
Can pilots reset an ICC or SPDA remote electronic circuit breaker?
ICC only by mx
Spud cb can be reset via the Mcdu.
How many networks make up the electrical system and why?
Two independent networks.
Redundancy and fault isolation.
