Electrical systems

Question 1

Three kind of current are available:

Answer 1

• Direct current (DC)
• Alternating current with constant frequency (AC)
• Alternating current with variable frequency (ACW)

Question 2

The two DC:

• starter
• generators

Answer 2

• From 0 to 45% NH as a NH starter mode

- Above 61,5% NH generator mode

Question 3

DC power voltage …

Answer 3

28 VDC

Question 4

The ACW Generator is driven by the … , and is available when …

Answer 4

• Reduction Gear Box

- NP > 66%

Question 5

Is there ACW available in Hotel Mode or with the propeller feathered ?

Answer 5

No

Question 6

When the propeller is unfeathered (CL in AUTO), the NP is maintained at a minimum of … , in order to have ACW
(minimum 66%)

Answer 6

70,8%

Question 7

The GND HDLG BUS is disconnected when …

Answer 7

Airborne

Question 8

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:

Answer 8

• The refueling panel is open
• The cargo door control panel is open
• The passenger door is open

Question 9

If the GEN are available, will the GPU operate ?

Answer 9

The GPU has always priority

Question 10

Batteries:

• MAIN
• EMER

Answer 10

• 24V Ni-Cd, 43 Ah

- 24V Ni-Cd, 15 Ah

Question 11

TRU (Emergency supply)

Answer 11

The TRU provides power to the emergency loads in case of dual DC generators loss.
It is supplied by the ACW bus 2.

Question 12

TRU

Answer 12

Transformer Rectifier Unit

Question 13

BTC

Answer 13

Bus Tie Contactors

Question 14

The BTC is used in case of generation failure, and it …

Answer 14

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)

Question 15

ACW to DC through TRU …

Answer 15

ACW power 115V/200V - DC power 28 VDC

Question 16

GCU

Answer 16

Generator Control Unit

- One for each generator and provides the control for the generator contactor and the start contactor

Question 17

BPCU

Answer 17

Bus Power Control Unit

- Provides control for BTC, BATTERY START CONTACTOR, load shedding, EXTERNAL POWER functions and SVCE BUS contactors

Question 18

The DC distribution consists of … buses and they are the following:

Answer 18

• 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

Question 19

SHED on the DC panel sheds the …

Answer 19

• DC SVCE BUS

- DC UTLY BUS 1 and 2

Question 20

How many static inverters are there ?

Answer 20

2

Question 21

The static inverters …

Answer 21

Convert ACW to AC constant frequency

Question 22

AC power (constant frequency)

Answer 22

• VAC 26 V

- VAC 115 V

Question 23

UNDV

Answer 23

DC STBY

Question 24

OVRD

Answer 24

Xfer/stby busses from HOT MAIN to HOT EMER BAT BUS

Question 25

Arrows

Answer 25

Emergency supply indicators (respective battery discharging)

Question 26

EMER BAT CHG - FAULT

Answer 26

Overheat detected by MFC or failure of contactor. ELEC on CAP. Contactor auto opens if: thermal runaway/bus voltage

Question 27

Bat sw - OVRD

Answer 27

Insures basic mode operation by overriding all other protections

Question 28

Bat sw - ON

Answer 28

- 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

Question 29

Bat sw - OFF

Answer 29

ESS BUS, DC STBY BUS + INV 1 are isolated from HOT MAIN BAT BUS DC EMER BUS is isolated from HOT EMER BAT BUS

Question 30

BTC

Answer 30

Allows BPCU to control BTC operation. Ext power, hotel mode or single gen operation, BTC is closed (green flow bar)

Question 31

BTC - ISOL

Answer 31

BTC and BTR opened (released | out)

Question 32

DC BUS OFF

Answer 32

Respective bus not supplied. ELEC on CAP

Question 33

EXT PWR - AVAIL

Answer 33

GPU has been checked by BPCU for over/under voltage, over current and polarity

Question 34

DC GEN 1 - FAULT

Answer 34

Generator FAULT Lt. Extinguishes above 61.5% NH if GEN is operating normally

Question 35

DC GEN 2 - FAULT

Answer 35

Protection trip by GCU; Auto reset if underspeed: in other cases manual. BTC auto closes

Question 36

DC SVCE/UTLY BUS

Answer 36

- 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

Question 37

ACW BUS OFF

Answer 37

Associated bus not supplied

Question 38

ACW GEN 1 /2 - FAULT

Answer 38

Auto reset in case of under/over speed: manual reset otherwise. ACW SVCE BUS auto shed if 1 GEN is out

Question 39

ACW GEN 2 and ACW GEN 1

Answer 39

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).