Electrics - Hydraulic Driven Generator Show Schematic Only

DC Electrical System.
main Battery APU Battery Battery Switch Battery Discharge Lights Static Inverter Standby Power Selector Switch Standby Power OFF Light Hot Battery Bus Battery Bus Standby DC Bus Standby AC Bus Left Main DC Bus Right Main DC Bus Center Buses As Installed Power will transfer providing at least 2 generators are operating and 3 autopilots armed for approach If there is a loss of power on one of the two DC buses, the DC BTB will close automatically. Left AC Transfer Bus Right AC Transfer Bus
AC Electrical System.
Start APU Connect External Power Shutdown Left Engine Shutdown Right Engine AC Buses and Load Shed System Generator Drive Disconnect Generator Drive Disconnect AC Bus Tie System AC Bus Tie System Generator Control Switch Generator Control Switch Ground Service Switch Ground Service Bus Ground Handling Bus - The Ground Handling Bus can only be powered on the ground by the APU or External Power. It cannot be powered from the engine-driven generators Left AC Bus OFF Light Right AC Bus OFF Light Left Flight Instrument Transfer Relay Right Flight Instrument Transfer Relay Left AC Bus Right AC Bus Captain's Flight Instruments Transfer Bus First Officer's Flight Instruments Transfer Bus

ETOPs Fitted
The hydraulic driven generator (HDG) activates automatically when both the left and right main AC buses are unpowered. The hydraulic driven generator is powered by the Left Hydraulic System.

The hydraulic driven generator provides AC power to the:

The hydraulic driven generator provides DC power to the:

The amount of DC power produced by the hydraulic driven generator is less than the DC power produced by a fully charged battery. When the hydraulic driven generator first begins to operate, the battery DISCH light may illuminate until the battery power decreases to the power level produced by the hydraulic driven generator.

The amount of DC power produced by the hydraulic driven generator is less than the DC power produced by fully charged main and APU batteries. When the hydraulic driven generator first begins to operate, the MAIN BAT DISCH and APU BAT DISCH lights may illuminate until the battery power decreases to the power level produced by the hydraulic driven generator.

System Operation