AUTO: The battery charge limiter controls automatically the connection and the disconnection of the corresponding battery to the DC BAT BUS by closing and opening of the battery line contactor.
The batteries are connected to the DC BAT BUS when:
APU is starting (MASTER SW at ON and N < 95%).
Battery voltage is below 26.5 V (battery charge).
Loss of AC BUS 1 and 2 when below 100 kt (EMER GEN not supplying power).
If AC BUS 1 and 2 are not energized and the EMER GEN is not supplying:
Battery 1 supplies the AC STAT INV BUS, and the AC ESS BUS only if speed is greater than 50 kt.
Battery 2 supplies the DC ESS BUS.
OFF: The battery charge limiter is not operating – the battery line contactor is open. DC BAT BUS is supplied. Hot buses remain supplied.
FAULT: The battery charge limiter is faulty. Amber light and ECAM caution, when charging current for the corresponding battery is outside limits. In this case, the battery contactor opens.
The flight crew can reset the contactors by switching the BAT pb-sw to OFF then to AUTO.
IDG pb (guarded)
The IDG switches are normally springloaded out. Pressing this switch disconnects the IDG from its driveshaft: only maintenance personnel can reconnect it.
FAULT: Amber light comes on, if:
IDG oil outlet overheats – above 180 °C, or
IDG oil pressure is low (inhibited at low engine speed: N2 below 14 %).
It extinguishes when the IDG is disconnected.
Automatic thermal disconnection of the IDG will occur if the temperature reaches 200 °C.
Maintaining the IDG pb for more than 3s may damage the IDG disconnection mechanism.
Disconnect the IDG only when the engine is running or windmilling. If not, the IDG will be damaged when starting the engine.
ON: If electrical parameters are normal, the generator is powered and the line contactor closes.
OFF: Generator is unpowered and the line contactors opens. The fault circuit is reset.
FAULT: Amber light and ECAM caution, if:
The associated generator control unit (GCU) trips it
Opening of the line contactor (except if the GEN pb is selected OFF).
APU GEN pb
ON: If electrical parameters are normal, the apu generator is powered and the line contactor closes. EXT PWR line contactor is open. The bus tie contactor closes automatically if GENs is not operating.
OFF: APU generator is unpowered and the line contactor opens. The fault circuit is reset.
FAULT: Same as GEN 1 or GEN 2 FAULT. APU GEN FAULT light is inhibited when APU speed is too low, or APU GEN line contactor opens after EXT PWR or ENG GEN takes over.
BUS TIE pb
AUTO: Bus tie contactors (BTCs) automatically open or close to maintain power supply to both AC BUS 1 and 2.
One contactor is closed, when One engine generator supplies the associated AC BUS, and APU generator, or external power supplies the other side.
Both contactors are closed during single-engine operation, or operation on the APU generator, or external power supply.
OFF: Both bus tie contactors open.
AC ESS FEED pb
NORMAL: AC ESS BUS is supplied by AC BUS 1.
Note – In case of normal AC ESS Feed failure, the AC ESS Bus is automatically fed from AC BUS 2 after 5 seconds, regardless of the pushbutton position.
ALTN: AC ESS BUS is supplied from AC BUS 2. Comes on when manually selected.
FAULT: Amber light and ECAM caution, if the AC ESS BUS is not electrically supplied.
Note – In case of a total loss of the main generators, the AC ESS BUS is automatically supplied by the emergency generator, or by the static inverter, if the emergency generator is not available.
GALY & CAB pb
AUTO: Cabin power is supplied – Main galley, secondary galley, in-seat power supply and IFE system (if installed). The power supply is dropped (shed) when only one generator is operating. All galleys are available when the APU GEN or EXT PWR is supplying power.
OFF: No power supply to the cabin.
FAULT: Amber light comes on when the load on any generator is more than 100% of rated output.
ON: All aircraft commercial electrical loads are supplied:
Cabin and cargo lights
Water and toilet system
Drain mast ice protection
Passenger entertainment system
Semi-automatic cargo loading (if installed)
OFF: Switches off all aircraft commercial electrical loads.
EXT PWR pb
AVAIL light comes on green if external power is plugged in, and external power parameters are normal.
If the AVAIL light is green a press will close the power line contactor and the white ON light comes on. The aircraft is now powered by external power.
If the AVAIL light is ON then a press will open the power line contactor and the white ON light goes off. The aircraft is no longer powered by external power.
External power has priority over the APU generator. The engine generators have priority over external power.
The ON light stays on, even when the engine generators supply the aircraft.