Electrical systems Flashcards
Three kind of current are available:
- Direct current (DC)
- Alternating current with constant frequency (AC)
- Alternating current with variable frequency (ACW)
The two DC:
- starter
- generators
- From 0 to 45% NH as a NH starter mode
- Above 61,5% NH generator mode
DC power voltage …
28 VDC
The ACW Generator is driven by the … , and is available when …
- Reduction Gear Box
- NP > 66%
Is there ACW available in Hotel Mode or with the propeller feathered ?
No
When the propeller is unfeathered (CL in AUTO), the NP is maintained at a minimum of … , in order to have ACW
(minimum 66%)
70,8%
The GND HDLG BUS is disconnected when …
Airborne
BAT OFF or BAT ON with the EXT PWR not available, the GND HDLG BUS is supplied by the HOT MAIN BAT BUS for ground
servicing only when:
- The refueling panel is open
- The cargo door control panel is open
- The passenger door is open
If the GEN are available, will the GPU operate ?
The GPU has always priority
Batteries:
- MAIN
- EMER
- 24V Ni-Cd, 43 Ah
- 24V Ni-Cd, 15 Ah
TRU (Emergency supply)
The TRU provides power to the emergency loads in case of dual DC generators loss.
It is supplied by the ACW bus 2.
TRU
Transformer Rectifier Unit
BTC
Bus Tie Contactors
The BTC is used in case of generation failure, and it …
Connects the networks (left and right)
- Allows DC BUS 1 and 2 on line when only one generator is operating (Hotel Mode operation or GPU)
ACW to DC through TRU …
ACW power 115V/200V - DC power 28 VDC
GCU
Generator Control Unit
- One for each generator and provides the control for the generator contactor and the start contactor
BPCU
Bus Power Control Unit
- Provides control for BTC, BATTERY START CONTACTOR, load shedding, EXTERNAL POWER functions and SVCE BUS contactors
The DC distribution consists of … buses and they are the following:
- 11
- Two main buses: DC BUS 1 and 2
- HOT MAIN BAT BUS and HOT EMER BAT BUS
- DC EMER BUS, DC ESS BUS and DC STBY BUS
- UTLY BUS 1 and 2
- DC SVCE BUS
- GND HDLG BUS
SHED on the DC panel sheds the …
- DC SVCE BUS
- DC UTLY BUS 1 and 2
How many static inverters are there ?
2
The static inverters …
Convert ACW to AC constant frequency
AC power (constant frequency)
- VAC 26 V
- VAC 115 V
UNDV
DC STBY
OVRD
Xfer/stby busses from HOT MAIN to HOT EMER BAT BUS
Arrows
Emergency supply indicators (respective battery discharging)
EMER BAT CHG - FAULT
Overheat detected by MFC or failure of contactor.
ELEC on CAP.
Contactor auto opens if: thermal runaway/bus voltage
Bat sw - OVRD
Insures basic mode operation by overriding all other protections
Bat sw - ON
- Basic mode: STBY busses supplied by HOT MAIN BAT BUS.
- Ext or gen power: DC STBY bus transferred to HOT EMER BAT BUS AC STBY BUS to DC BUS 1
Bat sw - OFF
ESS BUS, DC STBY BUS + INV 1 are isolated from HOT MAIN BAT BUS DC EMER BUS is isolated from HOT EMER BAT BUS
BTC
Allows BPCU to control BTC operation. Ext power, hotel mode or single gen operation, BTC is closed (green flow bar)
BTC - ISOL
BTC and BTR opened (released
out)
DC BUS OFF
Respective bus not supplied.
ELEC on CAP
EXT PWR - AVAIL
GPU has been checked by BPCU for over/under voltage, over current and polarity
DC GEN 1 - FAULT
Generator FAULT Lt. Extinguishes above 61.5% NH if GEN is operating normally
DC GEN 2 - FAULT
Protection trip by GCU;
Auto reset if underspeed: in other cases manual.
BTC auto closes
DC SVCE/UTLY BUS
- In automatic shedding
One of the DC SVCE/UTLY 1 and 2 busses is shed 1 bus SHED (BCPU).
ELEC on CAP. - In OFF
All DC SVCE/UTLY 1 and 2 busses are shed DC SVCE supplies power in flight and on ground during airplane servicing operations.
UTLY BUSSES suplly nonessential loads
ACW BUS OFF
Associated bus not supplied
ACW GEN 1 /2 - FAULT
Auto reset in case of under/over speed: manual reset otherwise.
ACW SVCE BUS auto shed if 1 GEN is out
ACW GEN 2 and ACW GEN 1
Min NP for ACW = 66 %.
The fuel governing mode maintains a MIN NP of 70.8% to be always above 66%.
The fuel governing mode is cancelled with the propeller feathered (No ACW).
