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737-600/700/800/900 TRAINING MANUAL

GENERATOR DRIVE DISCONNECT SWITCH (BEHIND GUARD)

737 GENERAL -GENERATOR DRIVE AND STANDBY POWER MODULE
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737-600/700/800/900 TRAINING MANUAL 737 GENERAL -- ELECTRICAL POWER - AC SYSTEMS, GENERATOR AND APU MODULE THIS PAGE INTENTIONALLY LEFT BLANK
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737-600/700/800/900 TRAINING MANUAL 737 GENERAL -- ELECTRICAL POWER - AC SYSTEMS, GENERATOR AND APU MODULE
General
The upper part of the AC systems, generator and APU module (P5-4) has these lights:
- GRD POWER AVAILABLE 
- TRANSFER BUS OFF 
- SOURCE OFF 
- GEN OFF BUS 
- APU GEN OFF BUS. 

The upper part of the module also has these manual controls:
-Ground power switch
-Engine generator switches
-APU generator switches
-Bus transfer switch.
GROUND POWER AVAILABLE Light
The GRD POWER AVAILABLE light is on when external AC power is connected and the quality is good. The light is bright blue when on.
Ground Power Switch
You use the ground power switch to control external power to the AC transfer buses.
TRANSFER BUS OFF Light
The amber TRANSFER BUS OFF light comes on when the AC transfer bus does not have power. There is one light for each AC transfer bus.
SOURCE OFF Light
The amber SOURCE OFF light shows when an AC transfer bus is not energized by the selected source. The left SOURCE OFF light is related to these sources:
-IDG 1 (GEN 1 switch)
-APU (left APU GEN switch)
-External power (ground power switch).
The right SOURCE OFF light is related to these sources:
-IDG 2 (GEN 2 switch)
-APU (right APU GEN switch)
-External power (ground power switch).
The SOURCE OFF light does not indicate that the AC transfer bus is de-energized. For example, in flight the left SOURCE OFF light comes on when generator control breaker (GCB) 1 trips. However, the bus transfer function lets IDG 2 power AC transfer bus 1.
There is one light for each transfer bus.

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737-600/700/800/900 TRAINING MANUAL 737 GENERAL -- ELECTRICAL POWER - AC SYSTEMS, GENERATOR AND APU MODULE
GEN OFF BUS Light
The blue GEN OFF BUS light comes on when the engine generator control breaker (GCB) is open. This shows that the IDG is not a power source in use. The light goes off when the GCB closes.
APU GEN OFF BUS Light
The blue APU GEN OFF BUS light shows that the APU is running, but its generator is not a power source in use. The light is on when the APU is running and the auxiliary power breaker (APB) is open. The light goes off when the APB closes or you shut down the APU.
Engine Generator Switches
The engine generator switches give manual control for IDG power source selection. Each switch is a three-position switch and is spring-loaded to the center (neutral) position. The ON and OFF positions are momentary positions.
You put a generator switch momentarily to the ON position to make that IDG the power source for its AC transfer bus. If IDG power quality is good, the electrical power system first removes the present power source (open its generator breaker). Then, the generator breaker for the IDG closes and the IDG now supplies power.
APU Generator Switches
The APU engine generator switches give manual control for APU generator power source selection. There are two switches because there are two bus tie breakers (BTBs). The switches operate like the engine generator switches.
Bus Transfer Switch
The bus transfer switch gives you manual control of the BTBs and the DC bus tie relay. The switch has two positions. The switch is usually in the AUTO position. A cover is a guard for the switch in the AUTO position.
In the AUTO position, the BTBs and the DC bus tie relay work automatically as necessary.
The BTBs and the DC bus tie relay open when the switch is put to the OFF position.

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00-00-00-250 Rev 1 03/17/1997

GROUND POWER SWITCH BUS TRANSFER SWITCH (BEHIND COVER)
FLIGHT COMPARTMENT ENGINE GENERATOR SWITCH (2)

TRANSFER 
BUS OFF  a 
SOURCE 
OFF  a 
GEN OFF 
BUS  b 

TRANSFER 
BUS OFF  a 
SOURCE 
OFF  a 
GEN OFF 
BUS  b 

APU GENERATOR SWITCH (2)

MAINT b  LOW OIL PRESSURE a  a FAULT  a SPEED OVER 

737 GENERAL - ELECTRICAL POWER - AC SYSTEMS, GENERATOR AND APU MODULE
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