Electrical System Flashcards
What type of electrical power does the CRJ 550 use?
115 Volt AC and 28 Volt DC.
What are the primary sources of AC electrical power?
2 engine driven integrated drive generators (IDGs) and 1 APU driven generator.
What are the sources of DC electrical power?
2 batteries and 4 Transformer/Rectifier Units (TRUs).
How is DC power distributed to the aircraft?
2 DC Power Centers (DCPCs)
Where are the batteries and TRUs located?
The APU battery is in the aft equipment bay and the main battery and TRUs are in the forward equipment bay.
What kind of batteries does the CRJ 550 have and what are they rated to?
Both are 24 volts. APU is 43 amps the main is 17 amps.
Other than the generators, how can AC power be provided to the system?
On the ground, through a Ground Power Unit (GPU) and in flight for emergencies through an Air Driven Generator (ADG).
Where are the circuit breaker panels located?
Behind the Captain and First Officer’s seats, and in the forward and aft equipment bays.
What is the purpose of the AC Power Centre (ACPC)?
It distributes AC power to the aircraft systems. It also provides a secondary power supply to the hydraulic pumps, flaps and slats, and pitch trim system.
What does the constant speed drive do?
Converts the variable RPM on the accessory gearbox to a constant Rpm output for the AC generator.
How are the components of the IDG displayed on the EICAS?
Next to the associated engine, the AC generator is labelled GEN and the constnt speed drive is labelled IDG.
Describe the CSD internal oil system.
Oil is cooled by air to oil heat exchanger using air from N1.
What causes an IDG FAULT switchlight to illuminate?
HOTLOP on the affected IDG.
How can the IDG be disconnected from the engine in the event of a fault?
Push the DISC switchlight on the electrical panel.
Can the IDG be reconnected in flight?
No.
If the IDG DISC switchlight fails, under what conditions would the CSD disconnect automatically?
CSD oil temperature reaches an unacceptably high level, also an input shaft will disconnect the IDG from the gearbox in the event of an over torque condition.
What controls and monitors the IDGs and the APU generator?
Generator Control Units (GCUs) that, in conjuncion with the ACPC, the GPUs provide voltage regulation, fault protection and bus priority for the AC system.
When will a generator be tripped offline?
Over or under voltage, over or under frequency, generator or bus over current or a generator phase seuence problem.
What priority does the ACPC give to power the AC buses?
Onside generator, APU generator, offside generator, ground power.
Can a tripped generator be reset?
Yes by QRH.
Can the APU genertaor supply AC power on its own?
Yes.
What does the green AVAIL light on the AC electrical panel indicate?
Ground power is available and acceptable.
What is the difference between the AC AVAIL switchlight on the overhead AC electrical panel and the similar switchlight on the external panel?
The switchlight on the flight deck will allow the groudn power to supply AC power to all buses (provided no other source is operating). The external switchlight will only supply AC power to the AC service bus (service configuration).
How can the bus priority logic be inhibited?
By depressing the automatic transfer switchlight on the AC electrical panel.
What happens if one of the Auto Transfer Inhibit switchlights is depressed?
The associated AC bus will only receive power from it’s onside generator. Allowing the crew to isolate each side of the AC power system if necessary.
What happens if the AC bus priority system detects a short in either AC BUS 1 or AC BUS 2?
It automatically limits the power source to the affected bus to its onside IDG.
Where does the AC ESSENTIAL BUS normally receive its power?
From AC BUS 1, regardless of what generator is powering it.
What happens to the AC ESSENTIAL BUS if the power source supplying AC BUS 1 fails?
AC BUS 2 automatically takes over and supplies power.
Can the AC ESSENTIAL BUS be powered if both AC BUS 1 and 2 lose power or fail?
Yes, through the ADG bus when the ADG is deployed.
What happens if the AC ESS XFER switchlight illuminates?
AC ESSENTIAL BUS is being powered by AC BUS 2.
How is the AC SERVICE BUS powered?
By AC BUS 2 or by external ground power.
How many TRUs are installed? And what are they rated at?
4 at 28 V.
How many batteries are installed?
2 at 24 V. The main battery is rated to 17 AMP and the APU battery rated to 43 AMP.
How many DC BUSES are installed?
9.
How is the DC electrical power distributed and controlled?
Through contactors controlled by the DC power controller (DCPC). All automatic, no pilot controls.
What are the TRUs rated at?
120 Amps.
Where are the TRUs located?
In the nose.
What is the purpose of the TRUs?
Convert 115 V AC power into 28 V DC power.
How are the main and APU batteries charged?
Through associated chargers. The main battery from AC BUS 1 and APU battery from AC SERVICE BUS.
What minimum voltage on the main and APU batteries is required for APU start?
22 V on both.
On the ground with only the main and APU batteries available, what DC buses are powered when the battery master switch is on?
APU BATTERY DIRECT BUS.
MAIN BATTERY DIRECT BUS.
DC BATTERY BUS.
In the air with only the main and APU batteriess available, what DC buses are powered?
APU BATTERY DIRECT BUS.
MAIN BATTERY DIRECT BUS.
DC BATTERY BUS.
DC ESSENTIAL BUS.
When would the battery chargers automatically shutdown?
Battery temperature exceeds 60 degrees C.
Battery fault.
Charger fault.
Which DC buses are always powered?
APU DIRECT BATTERY BUS.
MAIN BATTERY DIRECT BUS.
DC EMERGENCY BUS.
What does the DC EMERGENCY BUS supply power to?
Engine and APU fire protection equipment.
Hydraulic shutoff valves.
Fuel shutoff valves.
How is the DC EMERGENCY BUS powered?
DC BATTERY BUS (battery master on).
APU BATTERY DIRECT BUS (battery master off).
Which DC bus is not displayed on the EICAS DC ELECTRICAL synoptic page?
DC EMERGENCY BUS (unless a fault was detected).
What is the purpose of the CROSS TIE CONTACTOR?
It closes to allow TRU 2 to power the DC ESSENTIAL BUS in the event that ESS TRU 1 and 2 fail.
What does the DC SERVICE SWITCH power when switched on?
The DC SERVICE BUS.
Nav lights etc.
What happens if either TRU 1 or 2 fails?
The MAIN TIE CONTACTOR closes to allow the operative TRU to power the DC system. Note the DC UTILITY BUS will be shed.
When will the ADG automatically deploy?
In the event of a loss of eithe AC or DC power.
How long is DC emergency power expected to last?
30 minutes.
How many times are we permitted to reset a generator?
Once.
What is powered by the ADG bus?
Hydraulic pump 3B.
Flaps/Slats at 1/2 speed.
Stab trim channel 2.
AC ESS bus.
