IEEE Electrification Magazine - December 2014 - 4

TECHNOLOGY LEADERS

More Electric Aircraft Trends
By Kaushik Rajashekara

HE MORE ELECTRIC AIRcraft (MEA) system is being
widely recognized as the
future for the aerospace industry to
meet the power demands of increasing electric loads, reducing aircraft
emissions, improving fuel economy,
and lowering the cost of the total system. The airframers, parts suppliers,
and even the military have been putting significant effort into converting
most of the pneumatic and hydraulic
systems in the aircraft to electric. The
Advisory Council for Aeronautics
Research in Europe has also set several goals to be achieved by 2020 for air
transportation. These include a 50%
reduction of carbon dioxide emissions through a drastic reduction of
fuel consumption; an 80% reduction
of nitrogen oxide emissions; a 50%
reduction of external noise; and a
green design, manufacturing, maintenance, and disposal product life cycle.
To meet these challenges, MEA
technologies are continually evolving,
and there is much opportunity for
improvement as systems continue to
be refined and enhanced. New MEAbased requirements for electric
engine starting, high-power inverters,
and bleedless environmental control
systems are also being introduced.
This has been further reinforced by
the successful application of many of

Digital Object Identifier 10.1109/MELE.2014.2365621
Date of publication: 9 February 2015

these technologies in
In an MEA system,
passenger aircraft such
the jet engine is optias the Boeing 787 and
mized to produce both
Airbus A380.
the thrust and the elecAlthough MEA architric power. Also, the
tecture offers significant
same electric machine
overall system benefits
that is coupled to the
in reliability, improved
engine can be used for
fuel efficiency, and
starting the engine and
reduced emissions, the
for generating electric
MEA concept imposes
power. An active frontincreasing demands on Kaushik Rajashekara.
end power electronic
the electrical power generation, converconverter and dc-dc converters can be
sion, and distribution. In addition, it has
used to generate the required dc voltto be safe, reliable, efficient, and fault
ages, thus eliminating the need for
tolerant. In a traditional airplane, the jet
autotransformer rectifier units. Most
engine is designed to produce thrust as
of the loads are electric, including dewell as pneumatic, hydraulic, and elecicing and the environmental control
tric power. Even in an airplane like the
system. Even the fuel, hydraulic, and
777, there is only 240 kVA of electric
oil pumps, which are mounted on the
power generation using two 120-kVA,
accessory gear box of the engine,
115-Vac, 400-Hz engine-driven generacould be driven by the electric motors.
tors and one 120-kVA, 115-Vac, 400-Hz
High-power-density electric
auxiliary power unit (APU)-driven genmachines, power electronics, and
erator. However, in the 787, there are
power distribution are the enabling
four 250-kVA engine-driven generatechnologies for the successful
tors of variable frequency (about
advancement of MEA. Conventionally,
360-800 Hz) and two 225-kVA APUfor power generation, mainly synchrodriven generators. In addition to pownous generators coupled to the propulering 230-V ac loads, the generators'
sion engines through the accessory
electrical power is converted into 115-V
gear box are used. Recently, several
ac and 28-V dc power to feed many of
other types of generators, such as
the legacy subsystems that require
permanent-magnet synchronous
more conventional power. In addition,
machines, switched reluctance, and
±270 V dc is derived from 230 V ac using
induction machines, have been examan autotransformer rectifier for powerined for power generation. Similarly,
ing the environmental control systems
(continued on page 39)
and for starting the engine.

I E E E E l e c t r i f i c ati o n M agaz ine / DECEMBER 2014

Table of Contents for the Digital Edition of IEEE Electrification Magazine - December 2014