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Electrical System
The electrical system consists of AC and DC power, distributed and controlled by 4 ICCs and 2 SPDAs. The IDGs are the main source of power with engines running. The APU generator is the secondary source of power. A CSD converts variable engine speed into constant generator speed (12000 rpm, 400 Hz).
Two independant networks provide segregation for fault isolation. IDG 1 from the left engine powers AC 1, while IDG 2 powers AC 2 and the AC ESS bus. Each AC bus powers a dedicated TRU, which supply DC buses and DC ESS buses. In case of a fault, power is provided from a source in the following priority:
One AC source can supply the entire electrical system. When a total loss of AC power occurs, the RAT automatically deploys, and the generator supplies all essential buses.
Control panel
| IDG AUTO | normal operation |
| IDG OFF | respective generator line contactor opens, and the respective IDG is tripped off |
| IDG DISC | used when amber LED illuminates, indicating an IDG 1/2 OIL EICAS message (hold switch in position for 1s) |
Schematic
EICAS messages
IDG 1/2 OFF BUS
IDG 1/2 OIL