IEEE Electrification Magazine - June 2014 - 35

work cycles. a great deal of effort and investment needs to
be made in conceptualization, research, design, development, and testing to demonstrate that an alternative electric drive matches/exceeds the robustness, reliability,
performance, and cost targets of the mechanical systems.
nevertheless, the power electronics-based propulsion system offers numerous advantages as stated above. these
features, coupled with rising fuel costs, make electric
drives increasingly attractive and cost effective.the power
electronics systems required for off-highway vehicles also
need a higher design standard than industrial drive systems, as they need to be designed for harsher operating
conditions. some of the issues and challenges result from
designing for the application environment itself, and others are from the nature of the vehicle.

Environmental Challenges
the key environmental challenges include the following.
xx
the operating temperatures range from -40 to 85 °c.
xx
the temperature cycles vary due to working shifts as well
as daily and seasonal climate changes resulting from the
geographical location of the vehicle. therefore, the storage
temperature needs to be considered; for example, -55 °c
storage could become a challenging
design problem; also, continued
storage about 45 °c could become a
design challenge if the service
inverters for vehicle applications
need to be stored beyond two years
at or above 45 °c .
xx
high humidity conditions accentuate thermal cycling effects and
accelerate wear mechanisms.
xx
Products are exposed to various
uncontrolled chemicals that
exist in the field or in the vehicle
environment.
xx
the environmental conditions can
be dusty/dirty/conductive/corrosive, such as for vehicles operating
in coal dust in a mine or in a salt
water atmosphere on a sea coast.
xx
Damage can be caused by highpressure washing, especially
while high-voltage electronics are
powered.
xx
Damage can be caused by exposure to rain, including
possible submersion.
xx
Damage can be caused by extreme vibration and shock
requirements along with continuous vehicle movement and flexing due to exposure to rough terrain.
xx
the enclosure must be environmentally sealed and
robust against external forces-sealing creates extra challenges during extreme temp cycling and max loading.
xx
the system must be protected from exposure to
electrostatic discharge, especially in low-humidity

environments without undermining the high-speed
signal integrity.

Operational Challenges
the important challenges pertaining to vehicle operation are
xx
the absence of regulated ac mains source on mobile vehicle
xx
fault conditions, such as winding short circuits, phase
to ground or phase to phase short circuits, over temperature, over-speed, overvoltage, and undervoltage.
xx
power cycle due to the continuously cycling nature of
the application
xx
electromagnetic compatibility (eMc) (conducted and
radiated emissions and susceptibility)-sensitive
electronics such as analog sensor and low-voltage
digital signals and components must be robust in the
presence of high e and h field strengths; the electric
drive system must also not affect other vehicle electrical, communication, or entertainment systems.

Safety and Field/Service Challenges
some of the safety, field, and service issues and challenges
include
xxx
vehicle and machine grounding issues, including
safety bonding (connections
between electric machines,
inverters, and vehicle frame)
xxhigh-voltage safety
xxx
service personnel and operator
training
xx
x
vehicle performance and reliability
versus cost tradeoffs/considerations
xxx
safely handling failure modes
and limiting vehicle downtime/
lost productivity
xxx
limp-home capability under fault
conditions
xxx
field issues (vehicles are often
located in extremely remote
areas that are difficult to access)
xx
x
ease of maintenance, preferably on
site with no special training required.

The application of
power electronics
becomes important
for higher energy
density, decreased
fuel consumption,
performance and
productivity
enhancements, and
desired protection,
diagnostic, and
safety features.

examples of Ruggedized
electric Drive Vehicle

there are numerous success stories to
share about heavy-duty, off-highway vehicle electrification
projects that have been turned into commercial products
and, over the years, have developed a proven record of performance and fuel savings. all of these products require ruggedized power electronics parts and systems designed for
harsh environment exposure in the demanding applications.

Joy Global Mining Vehicles
in september 2008, Joy Global Mining, formerly known as
letourneau technologies, launched a mining-class loader,
	

IEEE Electrific ation Magazine / j une 2 0 1 4

35



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

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https://www.nxtbook.com/nxtbooks/pes/electrification_december2021
https://www.nxtbook.com/nxtbooks/pes/electrification_september2021
https://www.nxtbook.com/nxtbooks/pes/electrification_june2021
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https://www.nxtbook.com/nxtbooks/pes/electrification_june2018
https://www.nxtbook.com/nxtbooks/pes/electrification_december2017
https://www.nxtbook.com/nxtbooks/pes/electrification_september2017
https://www.nxtbook.com/nxtbooks/pes/electrification_march2018
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