Electrical Panel Flashcards
ELECTRICAL PANEL
DRIVE light (amber) illuminates
- 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)
ELECTRICAL PANEL
TR UNIT light
- illuminates on ground if any TR has failed
- illuminates in flight if TR1 failed or TR2 and TR3 failed
ELECTRICAL PANEL
SOURCE OFF light (amber)
illuminated
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
ELECTRICAL PANEL
CAB/UTIL switch
- Description
- What happens if there is an overload condition
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
ELECTRICAL PANEL
STANDBY POWER switch
BAT
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
ELECTRICAL PANEL
ELEC light
- operates only on the ground
- illuminates if a fault exists in the DC or the standby power system
ELECTRICAL PANEL
GENERATOR DRIVE DISCONNECT switch
description
disconnects IDG if engine start lever in IDLE and engine is turning
if disconnected can only be re-engaged on ground via reset handle
ELECTRICAL PANEL
GROUND SERVICE switch
lets you power AC and DC ground service buses directly from external power source
ELECTRICAL PANEL
BUS TRANSFER switch
AUTO
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
ELECTRICAL PANEL
STANDBY POWER switch
AUTO operation
-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
ELECTRICAL PANEL
TRANSFER BUS OFF light (amber)
illuminated
transfer bus not powered
ELECTRICAL PANEL
STANDBY POWER switch
OFF
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
ELECTRICAL PANEL
BAT DISCHARGE light illuminated
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
ELECTRICAL PANEL
BUS TRANSFER switch
OFF
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
ELECTRICAL PANEL
STANDBY POWER OFF light (amber)
illuminated
indicates one of the following buses are unpowered
- AC standby bus
- DC standby bus
- Battery bus (with BATT switch ON)
