(3)
Lightning Protectors (Fig. 6)
(a)
The lightning protectors consist of a varistor in series with a SCR (silicone controlled rectifier) with one varistor and SCR for each direction of current. The associated control circuit supplies a turn-on gate signal to the associated SCR when the impressed voltage exceeds 264 |12 volts. The result is a momentary short-to-ground effect which reduces the voltage to a low value for one-half cycle (400 Hz) or less which, in turn, causes the SCR gate signals to be removed.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
24-21-00
ALL ú ú 03 Page 7 ú Jun 10/90
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
3. 400 HZ 120/208V AC
DC
3. 80V AC NO LOAD MAIN GENERATOR
EXCITER
GENERATOR
ROTATING
PERMANENT RECTIFIERS
MAGNET
GENERATOR
.A
.B
.C EXCITER
MAIN FIELD
ROTATING RECTIFIERS
PERMANENT MAGNETIC GEN (PMG)
IDG
.A .B .C .A .B .C
PERMENANT MAGNET TRANSFORMER OUTPUT GENERATOR CURRENT GENERATOR OUTPUT
CURRENT
TRANSFORMER
ASSEMBLY
NEUTRAL
ROTOR SHAFT
N
T1 GENERATOR
T2
OUTPUT T3
EXCITER
FIELD
INPUT
Auxillary Power Unit Generator Block Diagram
Figure 5
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
24-21-00
ALL ú ú 02 Page 8 ú Feb 10/89
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
AC BUS X1
X2
GROUND
Lightning Protector Simplified Schematic Figure 6
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
24-21-00
ALL ú ú 01 Page 9 ú Feb 10/89
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
APU-DRIVEN GENERATOR QUICK ATTACH-DETACH (QAD) RING - REMOVAL/INSTALLATION
__________________________________________________________________________
1. General_______
A. This procedure has two tasks. One task is the removal of the quick attach-detach (QAD) ring for the APU-driven generator. The other task is the installation of the QAD ring.
B. The QAD rings are installed on the load gearbox on the APU. Access is through the APU access doors.
C. You must remove a APU-driven generator before you remove its QAD ring.
TASK 24-21-02-004-001
2. APU-Driven Generator Quick Attach-Detach (QAD) Ring Removal (Fig. 401)___________________________________________________________
A. References
(1)
24-21-03/401, APU-Driven Generator
(2)
IPC 49-51-02 Fig. 1
B.
Access
(1)
Location Zone
317 APU Compartment, LH
318 APU Compartment, RH
(2)
Access Panel
317AL APU Access Door
318AR APU Access Door
C.
Procedure
(1)
Remove the applicable APU-driven generator (Ref 24-21-03/401).
S 034-003
(2)
Remove the eight screws that attach the QAD ring to the APU load gearbox.
(3)
Remove the QAD ring from the APU load gearbox.
S 014-002
S 024-004
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
24-21-02
ALL ú ú 03 Page 401 ú Oct 10/90
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
SEE A
FWD
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：747-400 AMM 飞机维护手册 ELECTRICAL POWER 电源 1(82)
