03 ata24 electrics 2012

Aviation Systems Design

Frederic ABADIE [email protected]

General Principles

Basic functions, Electrical Sources

Electrical Power Line architecture

Electrical Generation

Engine driven generators

Ram Air Turbine

External Ground Cart

Electrical Distribution

Power Distribution Centre

Components :

Circuit Breakers : C/B, RCCB, SSPC

Transformers

More Electric Aircraft

2012-2013 2 Aviation Systems Design

General Principles





Ram Air Turbine




Components :


Transformers



Basic functions of Electrical System :

Generate electrical power required by Aircraft electrical loads, insuring power quality in all aircraft configurations

Distribute electrical power to the consumers

Provide information to the crew (status & alerts, maintenance info...)

Aircraft electrical sources


Flight / Ground Engine electrical generator Alternative (AC)

Flight / Ground Auxiliary Power Unit electrical generator

Alternative (AC)

Flight Ram Air Turbine Alternative (AC)

Flight / Ground Batteries Continuous (DC)

Ground External Ground Cart Alternative (AC)

AC : Alternative Current DC : Direct Current

Architecture : Electrical Power Line


DC busbar 28 VDC

DC Power Contactor

Transformer Rectifier

Unit AC Power Contactor AC busbar

115 or 230 VAC 400 Hz or VF

AC Generator

AC Circuit Breaker

AC Network can be: 115VAC or 230 VAC Fixed Frequency (400 Hz ) or Variable Freq

Segregated Power lines

Normal Circuit

- Feeding all consumers

- Powered from :

Engines

APU

Essential Circuit

- Feeding essential A/C functions

Flight Controls

Main pumps : Fuel, Hydraulics

Cabin pressurisation...

- Powered from :

Engines

APU

RAT

Batteries


General Principles





Ram Air Turbine




Components :


Transformers



1st Generation : Integrated Drive Generator (IDG)

AC generator driven by the engine through the gearbox (variable speed ~ 4 500 / 9 000 rpm)

Equipped with Constant Speed Drive (CSD) to regulate rotation speed to constant value

Usual rating : 70 kVA to 150 kVA

Characteristics : 115 VAC , 400Hz ; 3-phases


New generation : Variable Frequency Generator (VFG)

AC generator driven by the engine through the gearbox (variable speed ~ 4 500 / 9 000 rpm)

Frequency : 400Hz < f < 800 Hz


Characteristics : 115 VAC to 230 VAC ; 3-phases


Electrical Regulation

Point Of Regulation (P.O.R.) : Quality of electrical generation must be measured at consumer busbar


Power

Contactor

Feeders

P.O.R.

towards

Generator

Control Unit

APU Generator

AC generator driven by the APU (running at constant speed)

Constant Frequency : 400Hz


115 VAC to 230 VAC ; 3-phases


Ram Air Turbine

Emergency power source, automatically

deployed when all others Electrical Generators

are lost

Operative above a given air speed (~100 knots)

Provides Electric and/or Hydraulic power

Typical rating : 50 to 150 kVA

Constant Frequency (~ constant speed)

115 VAC to 230 VAC ; 3-phases


External Ground Cart (Ground Power Unit)

AC generator : 115 VAC , 400Hz +/- 5Hz , 3-phases

Typical power : 90 kVA per A/C plug


General Principles





Ram Air Turbine




Components :


Transformers




Cabinet including :

Energy distribution busbars : Low impedance copper or aluminium bars for consumers connection

Power source switching devices (contactors, relays)

Aircraft harness protections (Circuit Breakers)


AC busbar 115 or 230 VAC 400 Hz or VF

DC busbar 28 VDC


Circuit Breakers (C/B)

Protective devices for electrical harnesses and equipments

2012-2013 17

3-phase C/B 50 A

Single phase C/B 3 A

C/B panel

C/B characteristics :

3-phase (115/230VAC) or single phase (115VAC / 28VDC)

Max current rating

Tripping time (~10s ms)

Monitored or not

In flight, Airbus does not authorise a pilot to reengage a C/B which tripped by itself, unless the Captain, using his/her emergency authority, judges it necessary for safe continuation of the flight. In this emergency case, only one reengagement should be attempted.

On the ground, the pilot may reengage the C/B provided the action is coordinated with the maintenance team and the cause of the C/B tripping is identified

FCOM (Flight Crew Operating Manual) extract :

Aviation Systems Design

Remote Controlled Circuit Breakers (RCCB)

Same tripping principle as classic C/B (thermal)

Remotely piloted in Open / Closed position through low power relay


RCCB allow to :

Monitor CBs in remote areas (out of the cockpit)

Centrally drive CB position through dedicated HMI in the cockpit

Circuit Breakers Monitoring

Manual C/B (if monitored) and Remote Controlled C/B position can be displayed to cockpit crew through Engine & Warning Display


Solid State Power Controllers (SSPC)

SSPC modules are semiconductor-based devices (FETs), integrated in Power Distribution Centre electronic cards. They are both :

Protection devices for aircraft wiring against overload (=Circuit Breaker)

Power supply switches for technical operation and load management (=Relay)

Main advantages:

~3 times lighter than C/B technology at equivalent switching power

Faster switching (~1 ms)

Programmable trip threshold I(t)

Enhanced monitoring (status, voltages, currents, temperatures)

No mechanical noise


Transformer / Rectifiers Units (TRUs)

Transformers allow to convert Alternative electrical power (Alternative Current) into Continuous electrical power (Direct Current = DC)

TR efficiency typically between 80% and 90%

Basic principle :

Specific TRUs can be reversible and usable as static inverters


General Principles





Ram Air Turbine




Components :


Transformers



Electrical vs Hydraulics ?

Weight reduction

Enhanced maintenance capability and lower maintenance cost

Low emissions, low noise

A trend for the whole aviation industry...

Fly-by-wire is a standard since 30 years, but progress keeps on :

Affected Systems : brakes, engine starter, thrust reversers, movable actuators, pumps

AIRBUS A380 and A350 from 3H / 2E to 2H / 2E

BOEING B787 3H / 2E but no Bleed

And others companies ...


New trends towards More Electric Aircraft :

Fuel cells :

Flight tested since end of the 1960s (NASA)

Power rating ~100s kW per stack

Pros : Emission-free

Cons : H is highly flammable Production uneasy Storage uneasy

Harvesting technology

Usable for low power devices

Not industrial-level yet


Italy, 2010

ENFICA FC Rapid 200

BOEING 2008

Airbus

Questions ?

03 ata24 electrics 2012

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