737 Flight Crew Operations Manual
Electrical -
System Description
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
D6-27370-866-EGP 6.20.11
Standby Power System
Normal Operation
The standby system provides 115V AC and 24V DC power to essential systems
in the event of loss of all engine or APU–driven AC power. The standby power
system consists of:
• static inverter
• AC standby bus
• DC standby bus
• battery bus
• hot battery bus
• switched hot battery bus
• main battery
During normal operation the guarded standby power switch is in AUTO and the
battery switch is ON. This configuration provides alternate power sources in case
of partial power loss as well as complete transfer to battery power if all normal
power is lost. Under normal conditions the AC standby bus is powered from AC
transfer bus 1. The DC standby bus is powered by TR1, TR2, and TR3; the battery
bus is powered by TR3; the hot battery bus and switched hot battery bus are
powered by the battery/battery charger.
Alternate Operation
Single Battery
The alternate power source for standby power is the battery. With the standby
power switch in the AUTO position, the loss of all engine or APU electrical power
causes the battery to power the standby loads, both in the air and on the ground.
The AC standby bus is powered from the battery via the static inverter. The DC
standby bus, battery bus, hot battery bus, and switched hot battery bus are powered
directly from the battery.
The standby power switch provides for automatic or manual control of power to
the standby buses.
In the AUTO position, automatic switching from normal to alternate power occurs
if power from either AC transfer bus 1 or DC bus 1 is lost.
Positioning the switch to BAT overrides automatic switching and places the AC
standby bus, DC standby bus, and battery bus on battery power. The battery switch
may be ON or OFF. If the battery switch is OFF, the switched hot battery bus is
not powered.
Positioning the standby power switch to OFF de–energizes both the AC standby
bus and the DC standby bus and illuminates the STANDBY PWR OFF light.
September 28, 2006
To Next Page
Loading...
