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ERJ 175 ELECTRICAL QUESTIONS AND ANSWERS
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ERJ 175 ELECTRICAL QUESTIONS AND ANSWERS
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ERJ 175 ELECTRICAL QUESTIONS AND ANSWERSHow many networks make up the electrical system? Why? - Answers--2 independent
networks
-Redundancy and fault isolation
What happens if a power generating source fails - Answers-But ties automatically
connect to provide no system degradation.
What components power the AC system? (6) - Answers--2 IDGs
-APU
-RAT
-Inverter
-AC GPU
What components power the DC system? - Answers--3 TRUs
-2 Lead Acid batteries
-1 DC GPU
How does the IDG maintain a stable power output? - Answers-Constant speed drive
attaches the IDG to the accessory gear box ABG.
What monitors and controls the IDGs? - Answers-Each has a Generator Control Unit
GCU.
Can one IDG supply the entire electrical system? - Answers-Yes
What will cause the amber IDG light on the overhead panel to illuminate? - Answers-
HOTLOP. High oil temperature, or low oil pressure.
If an IDG is manually disconnected can it be reconnected by the flight crew? - Answers-
No, this is a maintenance only function.
What is the primary purpose of the AC generators? - Answers-To provide power to the
AC BUS and AC ESS BUSSES that power the 3 TRUs.
What is the purpose of the TRUs? - Answers-To convert 115VAC to 28VDC
Can the APU replace a failed IDG? - Answers-Yes, up to 33,000'.
What is the AC electrical system priority? - Answers--Onside IDG
-Inside APU
-Outside GPU
-Cross Side IDG
, How do you know that an AC GPU is hooked up to the airplane and ready to provide
electricity? - Answers-The GPU button displays AVAIL and the GPU icon is presented
on the electrical synoptic page. Once the button is pushed in, it will display IN USE
provided another AC power source is not available.
What does it mean if the AC GPU is plugged in and the outside GPU panel button
displays IN USE? - Answers--The ground service bus is in use.
-The cockpit GPU button will display AVAIL even though the ground service bus is in
use.
If the airplane is using the AC GPU and the APU is started, what should you be sure to
do? - Answers-De-select the GPU button.
What will charge the batteries? - Answers-Any AC power source through the TRUs.
How long will the aircraft's batteries last with no recharging? - Answers-10 minutes.
What is the purpose of the DC GPU? (2) - Answers--For APU start when the batteries
charge is less than 21VDC.
-If the temperature is below -20 C, to warm up the batteries.
What is the minimum BATTERY temperature for APU start? - Answers--20 C
What is the minimum battery voltage to close the battery bus-ties? - Answers-18V
What battery is used for the APU start? - Answers--Battery 1 power the FADEC and
EICAS
-Battery 2 powers the APU start bus
What is the purpose of the inverter? - Answers-To convert 28VDC to 115VAC to power
the AC STANDBY BUS when an AC power source is not available.
What is on the AC STANDBY BUS? - Answers-Engine exciters 1A and 2A
What is on the AC ESS BUS? - Answers-Slat channel 1, flap channel 2, AC Fuel pump
2, AC Hyd pump 3A.
What does the RAT power? - Answers-ESS BUSSES.....
3 = Hydraulic pump 3A
2 = AC Fuel pump 2
2 = Slat channel 2
1 = Flap channel 1
What powers the RAT? - Answers-Airflow turns the propeller which turns the turbine
inside.
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