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B777 Electrical power > Electrical > Flashcards

Electrical Flashcards

Electrical

1
Q

What is the purpose of ELMS?

A

ELMS (Electric Load Management System) provides load management and protection to ensure power AVBL to essential equipment.

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2
Q

What loads can be shed by ELMS?

A

Galleys first, the utility busses, then individual equipment items powered by main AC busses.

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3
Q

What indication is there of ELMS load shedding?

A

LOAD SHED message displays on electrical synoptic.

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4
Q

List the main electrical sources?

A

• L & R IDGs. • APU generator. • Primary & secondary external power.
(ACFT also has BUGs [back up generators], RAT [Ram Air Turbine] and battery).

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5
Q

What will cause illumination of the DRIVE light?

A

IDG low oil pressure.

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6
Q

What causes an automatic disconnection of the IDG?

A

IDG high oil temperature.

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7
Q

When will the APU start automatically?

A

When no other source of power becomes AVBL when the APU generator becomes AVBL (both transfer busses are unpowered).

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8
Q

When does the external power AVAIL light illuminate?

A

When external power source voltage & FREQ is connected and W/in limits.

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9
Q

What is the generator priority for the main busses?

A

Respective IDG à APU generator à opposite IDG.

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10
Q

What is the normal source for the Ground Service Bus?

A

R main AC bus.

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11
Q

How is the Ground Service Bus powered without supplying the main busses?

A

• APU generator. • Primary external power.

CX ACFT have a Ground Service switch at in the cabin at door L1

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12
Q

What loads are supplied by the Ground Service Bus?

A

• Main battery charger. • APU battery charger. • Miscellaneous cabin & system loads.

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13
Q

When is the Ground Handling Bus powered?

A

On GND only.

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14
Q

. What loads are supplied by the Ground Handling Bus?

A

• Cargo handling & lighting. • Refuelling/defuelling operations. • Other equipment energised only during GND operations.

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15
Q

What is supplied by the backup AC electrical system?

A

• R AC transfer bus. • R DC bus. • F/O’s FLT instrument bus.

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16
Q

What unit converts the back up generator frequency?

A

FREQ converter.

17
Q

How many backup generators can be used at a time?

A

1 (since BUGs have same input).

18
Q

What are the PMGs in the backup generator used for?

A

To supply DC power to FLT control power supply assemblies (FCDCs).

19
Q

Which AC busses supply the TRUs?

A

L & R AC transfer busses.

20
Q

What normally powers the hot battery bus?

A

Main battery charger.

21
Q

What is the purpose of the APU battery?

A

Provides power to APU electrical starter (used when insufficient bleed air for APU turbine starter). .

22
Q

What is the secondary power source for the C FCDC PSA?

A

Captain’s FLT instrument bus.

23
Q

Which FCDC PSAs can be powered by the hot battery bus?

A

L & C PSAs only.

24
Q

What is the purpose of the dedicated PSA battery?

A

To avoid power interruptions to the related FLT control DC bus

25
Q

What type of power is provided by the standby electrical system?

A

DC & AC power.

26
Q

What does the standby electrical system supply?

A

• FLT instruments. • Communication & navigation equipment.

27
Q

When does the standby inverter supply the AC standby bus?

A

When L transfer bus is not powered.

28
Q

What does the RAT generator supply?

A

STBY power to C1 & C2 TRUs.

29
Q

What are the altitude and airspeed limitations of the RAT generator?

A

None (operates at all ALTs & airspeeds)

30
Q

What supplies power until the RAT RPM is sufficient?

A

Main battery.

31
Q

What will cause automatic deployment of the RAT?

A

• Both AC transfer busses lose power in FLT. • Both engines are failed and C system pressure is low. • All 3 hydraulic system pressure are low.

B777 Electrical power (1 decks)

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