Electrical Panel Flashcards

1
Q

ELECTRICAL PANEL

DRIVE light (amber)
illuminates
A
  • IDG oil pressure low (engine not running or manual disconnect of IDG with gen drive disconnect switch)
  • under frequency fault with engine running
  • IDG automatically disconnected due to high oil temp
  • disconnected through gen drive DISCONNECT switch

Light controlled by GCU (Generator control unit)

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2
Q

ELECTRICAL PANEL

TR UNIT light

A
  • illuminates on ground if any TR has failed
  • illuminates in flight if TR1 failed or TR2 and TR3 failed
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3
Q

ELECTRICAL PANEL

SOURCE OFF light (amber)
illuminated

A

no source has been manually selected to power related transfer bus or the manually selected source disconnected

does not indicate AC transfer bus is de-energized
e.g. in flight - left SOURCE OFF light comes on GCB 1 trips, but, bus transfer function lets IDG 2 power AC transfer bus 1

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4
Q

ELECTRICAL PANEL

CAB/UTIL switch

  • Description
  • What happens if there is an overload condition
A

Powers:

  • left and right recirc fans
  • fwd and aft door area heaters
  • 115v AC galley buses
  • logo lights
  • potable water compressor

If an overload condition is sensed the bus power control unit (BPCU) sheds galley buses and main buses until load within limits

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5
Q

ELECTRICAL PANEL

STANDBY POWER switch
BAT

A

activates sby power system

  • AC sby bus powered by batteries or chargers through static inverter
  • DC sby bus and battery bus powered directly from batteries or chargers
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6
Q

ELECTRICAL PANEL

ELEC light

A
  • operates only on the ground

- illuminates if a fault exists in the DC or the standby power system

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7
Q

ELECTRICAL PANEL

GENERATOR DRIVE DISCONNECT switch
description

A

disconnects IDG if engine start lever in IDLE and engine is turning

if disconnected can only be re-engaged on ground via reset handle

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8
Q

ELECTRICAL PANEL

GROUND SERVICE switch

A

lets you power AC and DC ground service buses directly from external power source

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9
Q

ELECTRICAL PANEL

BUS TRANSFER switch
AUTO

A

BTBs (bus tie breaker), DC cross bus tie relay and TR3 transfer relay work automatically

one source fails, other power source automatically furnishes power to both transfer buses (through BTB)

energizes (closes) DC cross bus tie relay; TR1 and TR2 operate in parallel

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10
Q

ELECTRICAL PANEL

STANDBY POWER switch
AUTO operation

A

-arms sby power system

With AC transfer busses powered
AC sby bus powered by
-AC transfer bus 1

DC sby bus powered by
-TR1, TR2, TR3

transfer from normal power to sby power occurs

  • loss of transfer bus 1
  • DC bus 1 power source

Loss of all AC power

  • AC sby bus powered by batteries through static inverter
  • DC sby bus powered by the batteries
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11
Q

ELECTRICAL PANEL

TRANSFER BUS OFF light (amber)
illuminated

A

transfer bus not powered

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12
Q

ELECTRICAL PANEL

STANDBY POWER switch
OFF

A

Deactivates sby power system

STBY POWER OFF light illuminates

de-energizes AC and DC sby buses and static inverter

Note: No QRH checklist directs this action

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13
Q

ELECTRICAL PANEL

BAT DISCHARGE light illuminated

A

Illuminates with

  • excessive battery discharge with BAT switch ON
  • does not illuminate if using AC power
  • normal if starting APU with DC power only
  • will illuminate MASTER CAUTION and ELEC annunciator except during APU battery start
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14
Q

ELECTRICAL PANEL

BUS TRANSFER switch
OFF

A

manual control of BTBs (bus tie breakers), DC cross bus tie relay and TR3 xfr relay

BTBs open, isolating transfer buses which prevents auto transfer of transfer buses

DC cross bus tie relay cannot energize (isolates DC bus 1 from DC bus 2)

TR3 transfer relay cannot energize

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15
Q

ELECTRICAL PANEL

STANDBY POWER OFF light (amber)
illuminated

A

indicates one of the following buses are unpowered

  • AC standby bus
  • DC standby bus
  • Battery bus (with BATT switch ON)
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