The A350 has 3 types of power sources which include: the engine generators (2 per engine), the APU generator and the emergency generator driven by the Ram Air Turbine (RAT). The electrical network includes:
An Auto Transfer Unit (ATU) converts the 230 V AC into 115 V AC to supply the 115 V AC network.
The No Break Power Transfer (NBPT) function:
The static inverter powers the AC EMER 1 115 V busbar in the following cases:
Each engine has two generators. These engine-driven generators are the primary sources of electrical power during normal operations.
This frequency ranges from 390 Hz to 800 Hz, depending on the N3 rotation speed of the engine.
The static inverter transforms DC power from BAT EMER 1 into AC 115 V power at a constant frequency of 400 Hz.
On ground with batteries only:
APU GEN IN OPERATION - "230 V" is a maximum APU generator voltage.
The voltage is normal between 230 V and 240 V.
The Airbus A350 has ____ batteries.
Batteries are connected to the DC network supplied by a transformer rectifier for charge. Two of the batteries are capable of supplying power temporarily in an emergency electrical configuration.
The RAT is on the right hand side of the aft belly fairing, and supplies power, when the aircraft speed is:
TOWING ON BATTERIES - In normal conditions, the DC network supplies the electrical power to the system required for towing (brakes, position lights, flight interphone, minimum flight deck lighting, and VHF). If normal network is not available, the towing is permitted on battery power only (BAT 1), for a limited duration.
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The Transformer Rectifiers (TRs) supply the DC network with a DC 28 V power from the AC 230 V power. There are _____ TRs
In ground servicing mode:
GROUND SERVICING MODE - The ground servicing electrical network is supplied, when:
If all AC 230 V busbars are lost, the RAT automatically extends, and the emergency generator connects to the emergency network.
The Airbus A350 AC generation is made of:
The external power units supply the aircraft by providing AC 115 V power at a constant frequency of 400 Hz. Each external power unit can supply up to _____. There is one External Power Control Unit (EPCU) per external power unit.
On ground, it is possible to connect as many as two external power units (EXT 1 and EXT 2). One external power unit is sufficient to supply the entire aircraft network, but depending on the demand, some loads may be shed.
Each engine generator supplies AC power to its assigned AC busbar (e.g. GEN 1A supplies AC 1A).
There are two Variable Frequency Generators (VFGs) and Generator Control Units (GCUs) / Overvoltage Protection Units (OPU) per engine generator. Each GCU controls and monitors one generator.
There is one Variable Frequency Generator (VFG) and Generator Control Unit (GCU) / Overvoltage Protection Unit (OPU) per engine generator. Each GCU controls and monitors one generator.
If AC power is not available (TR 1 and TR 2 not operative), or during any source transfer, the DC 1 and DC 2 busbars are automatically connected to their corresponding batteries. As a result, the DC network is a No Break Power Transfer (NBPT) network.
The NBPT prevents busbar power interruption during source transfer. It is available on ground and in flight
REFUEL ON BATTERIES - In normal conditions, the DC network supplies DC power to refuel the aircraft. If the normal network is not available, batteries (BAT 1 and BAT 2) can supply the electrical power for refuel operation. The duration of the refuel on batteries is limited to _____ (with nominal batteries capacity).
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An external oil system lubricates and cools the engine generators.
An internal oil system lubricates and cools the engine generators.
The Generator Control Unit (GCU):
BAT 1(2)(EMER 1)(EMER 2) VOLTAGE INDICATION - What does a blank indication mean?
If the battery is confirmed inoperative, maintenance action is due.
In flight, if the entire normal AC network (AC 1A, AC 1B, AC 2B, and AC 2A busbars) is lost, the RAT will be deployed to recover the complete emergency AC network and the following rule is applicable for the APU:
BUS TIE CONTACTORS - The BUS TIE contactors function:
The APU generator frequency ("400 HZ") is considered normal when the indication is in between 385 Hz and 418 Hz.