IEEE Electrification Magazine - June 2014 - 54

such as fuel, oil, and hydraulic pumps. In an MEA system,
the jet engine is optimized to produce the thrust and electric power, as shown in Figure 5. The electric machine is
used for starting the engine and generating electric power.
Most of the loads are electrical, including the de-icing and
environmental control systems. The fuel, hydraulic, and oil
pumps are all driven by the electric motors.
The aircraft's electrical components operate on many different voltages, both ac and dc. However, most of the aircraft's systems use 115 Vac at 400 Hz and/or 28 Vdc. The A380
was the first large civil aircraft to incorporate the More Electric architecture system with VF power generation. The main
characteristics of the A380 electrical power generation
systems are:
xx
four 150-kVA VF generators (370-770 Hz)
xx
two 120-kVA CF APU generators (nominal 400 Hz)
xx
four external power connections (400 Hz) for ground
power.
The main electrical loads include:
xx
cabin lighting of approximately 15 kVA
xx
galleys of about 120-240 kVA intermittent load
depending upon the meal service
xx
galley cooling of approximately 90-kVA permanent load
xx
in-flight entertainment of about 50-60 kVA or about
100 W/seat permanent load.
The dc system is based on 28 V and is derived from the ac
bus using a transformer rectifier unit (TRU). The dc system also
provides power to the critical loads in case there is a power
interruption from the main power dc bus. The dc is also used
to charge the batteries and power the control computers.
The Boeing 787 has most of the features of an MEA system. The use of bleed air from the engines for powering the
environmental control and other systems is essentially eliminated, and the hydraulic actuators in use are powered

electrically. A key feature is the generation of three-phase
230-Vac electric power with VF (about 360-800 Hz) compared
with the conventional three-phase 115-Vac, 400-Hz power
system. There are two 250 kVA VF starter/generators per
engine, resulting in 500 kVA of generated power per engine.
Additional power is provided by two 225-kVA APU starter/
generators, each one being driven by the APU engine. In
addition to powering 230-Vac loads, the generators' electrical
power is converted into 115-Vac and 28-Vdc power to feed
many of the legacy subsystems that require more conventional power. Also + / - 270 Vdc is derived from 230 Vac using
autotransformer rectifier for powering the environmental
control systems and starting the engine.
The airframers and suppliers are also investigating the
feasibility of operating at higher dc bus voltages within the
airplane. Because of the similarity of the dc voltages in
MEAs and EVs/HEVs, the components developed for automotive systems could also be used in MEA systems, wherever possible, with little or no modification.

Integrated Starter/Generator System
for eVs/HeVs and embedded Generation
System for Aircraft

In HEVs, the power electronics and the electric motor are
mounted close to the engine. In the integrated starter/generator system, such as in the Honda Insight, the electric machine
is mounted between the engine and the transmission, as
shown in Figure 6. Therefore, the electric machine must be
designed to meet the engine operating temperature environment (Figure 7). Generally, the power electronics unit is also
installed in the engine compartment. Hence, novel heatmanagement techniques are needed to extract heat in high
power density systems.
To improve reliability, reduce the component counts,
meet the demand for future increases
in aircraft electrical power requirements, and also operate the generaJet Fuel
tors in VF mode, the air framers and
the engine manufacturers are examJet Engine
Thrust for Propulsion
ining the use of embedded generators
mounted directly onto the engine
shafts. Using the embedded electric
machine as a motor provides the
immediate benefit of electrical engine
Gearbox-Driven Units
High-Pressure
starting, thus making the conventionAir from the Engine
al air starter obsolete. Also, direct cou(Bleed Air)
pling of the electrical machine to the
engine shafts means that the power
Electric
Hydraulic
Oil Pump
Fuel Pump
Pneumatic Loads
Generator
Pump
take-off shaft and associated gearbox
Such as Environmental
can be removed, reducing the size
Control System
and weight of the aircraft. Furthermore, the oil, fuel, and hydraulic
Pneumatic
Other
pumps could be driven electrically
Electric Loads
Starter
Accessories
instead of from the high-pressure
(HP) shaft of the engine, as shown in
Figure 4. A traditional aircraft system.
Figure 8. In addition, generators can

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

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