737 Flight Crew Operations Manual
Electrical -
Controls and Indicators
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
D6-27370-866-EGP 6.10.7
1 Ground Power Available (GRD POWER AVAILABLE) Light
Illuminated (blue) – ground power is connected and meets airplane power quality
standards.
2 Ground Power (GRD PWR) Switch
Three position switch, spring–loaded to neutral
OFF – disconnects ground power from AC transfer busses.
ON – if momentarily moved to ON position and ground power is available:
• removes previously connected power from AC transfer busses
• connects ground power to AC transfer busses if power quality is correct.
3 TRANSFER BUS OFF Lights
Illuminated (amber) – related transfer bus is not powered.
4 SOURCE OFF Lights
Illuminated (amber) – no source has been manually selected to power the related
transfer bus, or the manually selected source has been disconnected
• if a source has been selected to power the opposite transfer bus, both
transfer busses are powered.
5 Generator Off Bus (GEN OFF BUS) Lights
Illuminated (blue) – IDG is not supplying power to the related transfer bus.
6 Generator (GEN) Switches
Three position switch, spring–loaded to neutral.
OFF – disconnects IDG from related AC transfer bus by opening generator circuit
breaker.
ON – connects IDG to related AC transfer bus by disconnecting previous power
source and closing generator circuit breaker.
7 BUS TRANSFER Switch
AUTO (guarded position) – BTBs operate automatically to maintain power to AC
transfer busses from any operating generator or external power
• DC cross tie relay automatically provides normal or isolated operation
as required.
OFF – isolates AC transfer bus 1 from AC transfer bus 2 if one IDG is supplying
power to both AC transfer busses
• DC cross tie relay opens to isolate DC bus 1 from DC bus 2.
September 24, 2015
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