Powering Freight & Transportation - Power Systems Design

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of the system would be whether bulky
heat sinks were needed for thermal
management. The weight, efficiency
and controllability specifications called
for the use of semi-customized circuit
modules, and Vicor was the only manufacturer
that could deliver modules that
were both sufficiently light-weight and
still met the efficiency, controllability and
volume specifications.
Implementation with a focus
on weight and efficiency
The charging subsystem is operated
by a dedicated controller, which
communicates with the glider’s system
computer via CAN bus. The charging
cycle is only activated after completion
of the other steps described
above. For space, weight and thermal
management reasons, the subsystem
is divided into two sections, the auto
ranging mains front-end and the power
section which contains the DC-DC
converters.
During a charging cycle, only the
power section generates substantial
heat. The glider electronics contain
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DC-DC converters are the heart of the charging system.
another element that generates substantial
heat during powered flight: the
motor control circuitry. Since motor and
charging electronics are never used at
the same time, the power section and
the motor control circuitry can share the
same heat sink, reducing weight. The
Vicor DC-DC converter modules contain
a metal base plate which serves both
to mount the module and to establish a
thermally conductive contact to a heat
sink, yielding a very compact, lightweight
design.
The battery
array consists
of 72 highperformance
Li-
Ion cells which
are connected
in series. The
batteries operate
with cell
voltages of
2.7V (‘empty’)
to 4.0V (‘full’),
so that the
circuitry has to
deliver a charge
voltage ranging
from 194V
to 288V, which
is determined
using a cell voltagemeasurement
which is
performed by
the charge controller
at regular
intervals. The
charge controller
derives a
trim voltage
from this mea-
surement and delivers it to the DC-DCconverters
so that the charge voltage
is updated in relation to the batteries’
status. The controller also limits the trim
voltage so that the converters cannot
deliver a higher voltage than 290V, thus
protecting the battery array against
overcharging. As it is only used on the
ground and not during flight operation
Lange did not need to implement any
redundancy in the charging system.
Due to the efficiency and light-weight
design of the deployed Vicor circuit
modules, the resulting charging unit only
weighs 6kg including cabling, freeing
more weight for valuable payload. The
unit consumes approximately 1.7kW
of mains power, and requires just nine
hours to fully recharge the glider’s batteries.
The auto ranging mains frontend
of the charger is compatible to mains
voltages from 110 to 230VAC, and is
thus usable world-wide.
Conclusion
The Antares glider’s self-contained
electrical drive system has moved
man’s flight one step closer to the
elegance and freedom of the birds. The
outstanding electrical power to weight
ratio and high efficiency of the Vicor
solution allowed the design team to
integrate the battery charging system
within the plane without compromising
the flight performance – something that
is crucial to the fascination and thrill of
glider flight.
electronica B2.311 & A5.313
www.vicoreurope.com
Power Systems Design October 2008
Powering Powering Freight Freight & Transportation
& Transportation
Progressing Freight and
Ultracapacitors in energy saving applications
A growing number of energy experts worry about the world's lack of preparation for “peak oil,”
a term referencing the point at which the amount of petroleum that is economically feasible to extract
and refine goes into decline. Peak oil does not mean running out of oil, but rather signifies the end
www.powersystemsdesign.com
of the cheap-fuel era.
By Sven Baechtiger, Key Account Manager, Heavy Transportation, Maxwell Technologies
Oil prices have plunged approximately
30% since surging to a
record $147.27 a barrel in July of
2008. Does this indicate that the crisis
is over? The US per capita oil consumption
is 25 barrels annually. Additionally,
both China and India are consuming
below 2 barrels for the collective population
of 2.5 billion citizens in these locations
and there is an expectation that oil
demand will increase in each of these
countries as more of their citizens look
to enjoy the fruits of the energy-hungry
world.
Maxwell Technologies believes industry
needs to alter its mindset in terms
of energy consumption and energy
management. The time when energy
was wasted without concern in braking
resistors, un-adapted diesel engines,
and in un-recovered kinetic energy, has
now gone.
Energy Storage Efficiency in
Transportation
Hybrid electric busses and cars are
today a familiar concept and can frequently
be seen in many of the
world’s cities. The use of an energy
storage device allows efficient startstop
operation as well as the recovery
of braking energy with fuel consumption
and CO 2 emissions significantly
reduced. These very same principles
are also applicable to heavier vehicles
in public transportation, such as trains,
Transportation
Figure 1. Wide temperature range and low internal resistance of Ultracapacitors outperform
Batteries.
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