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AIRCRAFT ELECTRICAL POWER GENERATION SYSTEM

GENERAL OVERVIEW

The aircraft electrical power system is supplied by:

(Main Turbofan Engines)

Engine DrivenAC Generators Driven by respective engines where the generator is installed.

APU drivenAC Generators This generator is installed along the APU.

(Main

Turboprop Engines)Engine Driven DC Generators* Driven by each respective engines where the generator is

installed.

APU driven DC Generators* This generator is installed along the APU, but often comes as an

optional system/component.*note: DC Generators for turboprop aircraft also becomes DC Motors when used for engine starting.

Ni-Cad Batteries

Primary purpose of aircraft Ni-Cad batteries is/are for emergency supply of electrical power to

the aircraft, prior to the availability of the emergency (RAT) generator, in the event of loss of

power to the Main Power Bus (DC Generator) or AC Main Busses.

Applicable for both turboprops and turbofan engine aircraft.

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DC GENERATION

DC Generation for turbofan aircraft is primarily obtained through the Transformer Rectifier

Units (TRUs) as called by Boeing, or just Transformer Rectifiers (TRs) as called by Airbus.

The DC electrical output from each TRs/TRUs then goes directly to DC Busses directly connectedto each respective TRs/TRUs.

EXTERNAL POWER SOURCE

The external power source or the ground power source may also be supplied to the aircraft

through the external power receptacles/connectors.

External power can supply the electrical power requirement of the aircraft while on ground

without the need for on-wing generators. Great fuel savings may be realized with the use of

external power on ground.

The external power is then supplied to all AC Main Busses.

EMERGENCY POWER GENERATION SYSTEMS OVERVIEW

EMERGENCY POWER GENERATION

Emergency power generation for most large turbofan engine aircraft such as those

manufactured by Boeing and Airbus has emergency generators that are driven by Ram Air

Turbine (RAT) through hydraulic power.

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BATTERIES ONLY POWER

In the event of loss of power and emergency generator has not yet supplied electrical power

either due to total generator power loss or when deployment of the RAT generator is in transit,

the batteries will supply the needed AC Electrical power through the STATIC INVERTER.

DC ESS BUSSES

The DC ESSential Busses are supplied by the ESSential TR/TRU in the event that electrical power

is supplied from the emergency generator.

The DC ESSential Busses may be supplied with electrical power directly from the battery (usually

BATT no.2) if the ESSential TR/TRU fails to supply electrical power to the DC ESS BUSSES.

AC ESS BUSSES

The AC ESS Busses are supplied with AC electrical power from theSTATIC INVERTER.

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NORMAL

CONFIG

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EXT PWR

CONFIG

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GRND SVC

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LOSS OF MAIN

GENERATOR

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EMERGENCY GEN

CONFIG