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747-400
MAINTENANCE MANUAL
6. Operation
_________
A. Functional Description
(1)
IDG Power Generation (Fig. 4)
(a)
The ac generator is a three stage brushless, rotating rectifier device, which contains a permanent magnet generator, exciter generator, and the main generator.
(b)
The permanent magnet generator supplies 3-phase alternating current power to the generator control unit (GCU) where it is converted to direct current power used for system control, protection, and generator exitation.
(c)
The generator control unit applies direct current voltage to the windings of the exciter stator, resulting in a direct current proportional to the applied voltage. The exciter stator windings are alternately reversed in polarity to produce a 10 pole direct current field in the stator.
(d)
Rotation of the exciter rotor in the field of the exciter stator induces an alternating current voltage in the windings of the rotor.
(e)
The rotating rectifier assembly consists of six silicon diodes connected in a three phase full-wave bridge. The axis of the diodes is parallel with the axis of generator shaft rotation. The rotating rectifier converts the alternating current voltage from the windings of the exciter rotor into direct current voltage, which is applied to the windings of the main generator rotor.
(f)
The output of the rotating rectifier creates a direct current in the windings of the main generator rotor to produce a magnetic field. The rotating magnetic field of the main generator rotor induces an alternating current voltage in the windings of the main generator stator as the rotor rotates in the stator.
(g)
The internal current transformer assembly provides differential current protection for the system when used in conjunction with an external current transformer assemebly and generator control unit.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
3., 1200 HZ CURRENT 102V AC TRANSFORMER
MAIN GENERATOR OUTPUT
EXCITER GENERATOR CURRENT PERMENANT MAGNET
FIELD TRANSFORMER OUTPUT GENERATOR OUTPUT
INPUT
Integrated Drive Generator Block Diagram
Figure 4
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
24-21-00
ALL ú ú 02 Page 6 ú Feb 10/89
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
(2)
APU Power Generation (Fig. 5)
(a)
The functional description of the ac generators on the APU are similiar to the ac generators of the IDG's with the exception of the rotating rectifier assembly. In the APU ac generator, the rotating rectifier assembly consists of three silicon diodes connected in a three phase half-wave bridge.
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