Ground Service Switch

GROUND SERVICE Switch
Momentary push–button switch.
Provides manual control of ground service busses. Enables servicing airplane
using external power without activating AC transfer busses.
Illuminated (white) –

.
ON – connects external power to ground service busses

.
OFF – disconnects external power from ground service busses.

Copyright . The Boeing Company. See title page for details.
Electrical -Controls and Indicators 737 Flight Crew Operations Manual

Intentionally
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Copyright . The Boeing Company. See title page for details.
6.10.14  September 26, 2003

737 Flight Crew Operations Manual

Introduction
Single Battery YA801 - YA803
Primary electrical power is provided by two engine integrated drive generators (IDGs) which supply three-phase, 115 volt, 400 cycle alternating current. Each IDG supplies its own bus system in normal operation and can also supply essential and non-essential loads of the opposite side bus system when one IDG is inoperative. Transformer rectifier (TR) units and a battery/battery charger supply DC power. The battery also provides backup power for the AC and DC standby system. The APU operates a generator and can supply power to both AC transfer busses on the ground or in flight.
There are two basic principles of operation for the 737 electrical system:
.  
There is no paralleling of the AC sources of power.

.  
The source of power being connected to a transfer bus automatically
disconnects an existing source.

The electrical power system may be categorized into three main divisions: the AC power system, the DC power system, and the standby power system.
Dual Battery YA613 - YA722, YA809 - YK104
Primary electrical power is provided by two engine integrated drive generators (IDGs) which supply three-phase, 115 volt, 400 cycle alternating current. Each IDG supplies its own bus system in normal operation and can also supply essential and non-essential loads of the opposite side bus system when one IDG is inoperative. Transformer rectifier (TR) units and the main battery/battery charger supply DC power. The main and auxiliary batteries also provide backup power for the AC and DC standby system. The APU operates a generator and can supply power to both AC transfer busses on the ground or in flight.
There are two basic principles of operation for the 737 electrical system:
.  
There is no paralleling of the AC sources of power.

.  
The source of power being connected to a transfer bus automatically
disconnects an existing source.

The electrical power system may be categorized into three main divisions: the AC power system, the DC power system, and the standby power system.
Copyright . The Boeing Company. See title page for details.
Electrical -System Description 737 Flight Crew Operations Manual

Electrical Power Generation Engine Generators
Primary power is obtained from two engine IDGs. The IDG maintains a constant generator speed throughout the normal operating range of the engine. An integral electro–mechanical disconnect device provides for complete mechanical isolation of the IDG.
APU Generator
The APU generator can supply power to both AC transfer busses on the ground or in flight. As the only power source, the APU generator can meet electrical power requirements for all ground conditions and most flight conditions.
External Ground Power
An external AC power receptacle located near the nose gear wheel well, on the lower right side of the fuselage, allows the use of an external power source. Status lights on a panel adjacent to the receptacle permit the ground crew to determine if external power is being used. When connected, external power can supply power to both transfer busses.
Ground Service
For ground servicing, a ground service switch is on the forward attendant’s panel. The switch provides ground power directly to the AC ground service busses for utility outlets, cabin lighting and the battery charger without powering all airplane electrical busses. The ground service switch is a momentary push button and is overridden when both AC transfer busses are powered.
Copyright . The Boeing Company. See title page for details.
6.20.2  July 28, 2000

Electrical -System Description
Electrical Power Schematic
YA801 - YA803

AIRPLANE CONFIGURATION - IN FLIGHT  BATTERY SWITCH - ON STANDBY POWER SWITCH - AUTO
 BUS TRANSFER SWITCH - AUTOENGINE GENERATOR CONNECTED TO RELATED BUS
Copyright . The Boeing Company. See title page for details.
Electrical -System Description

YA613 - YA722, YA809 - YK104

AIRPLANE CONFIGURATION - IN FLIGHT  BATTERY SWITCH - ON STANDBY POWER SWITCH - AUTO
　
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