S 864-008
 (3)  
Remove the DO-NOT-OPERATE tag from the APU switch.

 D.
Do a Test of the Auxiliary Generator Control Unit

 (1)  
Supply electrical power (Ref 24-22-00/201).

 S 714-010

 (2)  
Do a test of the AGCU:

 (a)  
Get access to the EXISTING FAULTS page for Chapter 24 (if any) on the CMCS (AMM 45-10-00/201).

 S 864-011
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747-400 MAINTENANCE MANUAL
 (b)
Make sure the CMCS messages for the AGCU do not show. S 864-012

 (3)
Remove electrical power, if it is not necessary (Ref 24-22-00/201).

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2.

3.

4.

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747-400 MAINTENANCE MANUAL
 115-VOLT AC STANDBY POWER GENERATION - DESCRIPTION AND OPERATION
________________________________________________________________
General
_______
 A.  The ac standby power system provides 115-volt ac power to flight critical loads (flight instruments, communications, and navigation equipment) for 30 minutes minimum in the event of complete loss of primary ac power. The system consists of a transfer relay, ac standby bus, static inverter, and control switch. The flight critical loads are connected to the ac standby bus, which receives power from either ac bus 3 or the main static inverter. The main static inverter is controlled by the standby power switch on the electrical system control module in the flight deck.
 B.  The APU static inverter provides 115-volt ac power and shares the flight critical loads with the ac standby bus in the event of a power loss of the the captain's transfer buses, primary and alternate.
Main Static Inverter (Fig. 1)
____________________
 A.  The function of the main static inverter is to convert 28-volt dc power from the main battery to 115-volt, single phase, 400 Hz ac power. The main static inverter is rated at 1 kva, 0.75 to unity power factor for an input voltage range from 18.0-36.0 volts dc. The output voltage is 115 |5 volts ac at 400 |5 Hz for 0-100 percent load range. The inverter is capable of supplying 100 percent rated load continuously with normal convection cooling. The inverter cannot be damaged when its output terminals are continuously short circuited. It is self-protected by an internal current limiting circuit that limits the output current to approximately 34 amps.
APU Static Inverter (Fig. 1)
___________________
 A.  The functon of the APU static inverter is to convert 28-volt dc power from the APU battery to 115-volt, single phase, 400 Hz ac power. The APU static inverter is identical to the main static inverter and are interchangeable.
Standby Power Switch
____________________
 A.  The standby power switch is a three position rotary switch located on the electrical system control module. The off (push to turn) position inhibits operation of the main static inverter and removes power from the APU static inverter. Auto position is for normal operation and the battery position (with main battery switch set to ON) applies the battery voltage to both the main static inverter and the APU static inverter to supply ac standby power from the static inverters to their respective buses.
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747-400
MAINTENANCE MANUAL

MAIN STATIC INVERTER

E-30 EQUIPMENT RACK
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Static Inverter Location
　
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