(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.

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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

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MAINTENANCE MANUAL

AC BUS X1

X2
GROUND
Lightning Protector Simplified Schematic Figure 6
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 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
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SEE A
FWD 
　
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