ATA 24 Electrics

Question 1

What is the main power concerning the electricsl systems for DHC-8?

Answer 1

28 VDC

Question 2

What is the minimum of power sources we need to power the entire DC bus system? (Without external power)

Answer 2

Two, one of each, TRU/GEN or both

Question 3

Is it possible for the AUX BATTERY to power the main feeder bus?

Answer 3

No

Question 4

When yoe select the Battery Master switch to ON position, which buses will then be powered?

Answer 4

L and R ESS BUS

Question 5

There is no bus-failure. You select the Main Bus Tie switch to MAIN BUS TIE position. What happens to the system?

Answer 5

L and R Main bus will be connected

Question 6

There has been a bus failure. You select the BUS FAULT RESET switch to RESET position. What is the purpose?

Answer 6

To resett the caution indication. The circuit closes for 7 seconds, then opens if the fault is still present

Question 7

Is it possible to supply the secondary bus by batteri power?

Answer 7

No

Question 8

What does an illuminated DC GEN caution light indicate?

Answer 8

Affected DC GEN offline, ext pwr or switched off

Question 9

What is the function of the TRU`s?

Answer 9

Converts 115 VDC power to 28 VDC

Supplies the secondary buses

Question 10

Both TRU`s are operating normal. What will happen if both DC Generators fails (not over current condition)?

Answer 10

The secondary bus ties closes and the TRU`s will supply power to the DC bus system

Question 11

What happened in the electrical power system if DC GEN #1 fails and the right engine fails/stops (flameout)?

Answer 11

AC GEN #1 will power both TRU’s

Question 12

What is the main purpose of the Bus Bar Protection Unit (BBPU)?

Answer 12

The bus tie contactors are controlled by the Bus Bar Protection Unit (BBPU) which inhibits them if a bus fault occurs. It also closes the contactors during engine starts so that left and right side buses can receive electrical power.

Protects GENs and batteries

Question 13

The following caution lights come on:
First DC BUS
Tehn after 7-10 seconds
MAIN BAT and 
DC GEN #2

What does that indicate?

Answer 13

Overspenning fra generator. BBPU har isolert MAIN BAT fra generator. R MAIN bus har kortsluttet i dette tilfellet

Question 14

How will a Battery Overtemp be indicated?

Answer 14

AUX BATT HOT or MAIN BATT HOT warning light illuminates ( flashes) as well as the Master Warning

Battery temp monitor: red scale

T > 65 degrees

Question 15

Where is the battery power bus located?

Answer 15

Lower part of the R ESS BUS panel

Question 16

Is there any protection against overvoltage coming from DC EXT. POWER?

Answer 16

Yes, an overcurrent protection will disconnect the external power if a a fault or overcurrent occur. Max voltage from an external power source is 31,5 volts

Question 17

Concerning the DC Power Monitor Panel: You have a flashing minus sign in front of the numeric value on the Main Battery Load Display. What does that indicate?

Answer 17

The system drains the Main Battery

Question 18

One AC GEN caution light comes on. What does that indicate?

Answer 18

The affected AC Generator is offline or has shut down

Question 19

An illuminated AC BUS caution light indicates what?

Answer 19

Bus fault (overcurrent/undervoltage). GCU indicates faulty bus

Voltage <90V undervoltage FAULT

Question 20

Primary and secondary Inverters has an ON-OFF switch, while the Auxiliary Inverter ha a three position switch. Why?

Answer 20

Because it serves as a backup for the primary and secondary inverters. If a fault occurs in one of the other, the auxiliary inverter can supply the affected side by switching it to L or R

Question 21

Where is the 115V/400Hz buses located?

Answer 21

L side circuit panel

Question 22

Concerning the AC Monitor Panel: The Inverter Selector switch is in the PRI positiom, you have a flashing Plus sign in front of the value 1.05 in the Inverter Load Display. What does it indicate?

Answer 22

Overload condition in the Inverter

Question 23

Where is the AC variable frequency buses located and what is the power source for them?

Answer 23

ON AC Variable frequency CB panel behind FO.

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