PRODUCTS & SERVICES
CURTISS-WRIGHT
A NEW INVERTER SERIES OFFERS STATE-OF-THE-ART TECHNOLOGY AND INNOVATIVE DESIGN
FOR USE IN HYBRID AND PURE-ELECTRIC VEHICLE APPLICATIONS
57
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iVTInternational.com November 2019
Curtiss-Wright has been
designing and manufacturing
vehicle-grade traction inverters since 2003. The
company estimates that its inverters – fitted to
medium- and heavy-duty trucks, buses and on- and
off-highway vehicles – have covered over 1.8 billion
kilometers of on-road use.
The kilometers covered by these traction inverters
have helped Curtiss-Wright during the development of
its recently launched WTI (world traction inverter) series,
which offers state-of-the-art technology and innovative
design for use in hybrid and pure-electric vehicles.
As a tier 1 supplier to numerous vehicle OEMs,
Curtiss-Wright is well placed to understand the
market’s needs, an understanding that has formed the
basis for the WTI.
The WTI series
Targeted at package/delivery vehicles or an implement in
an off-road environment, the WTI-S160 offers a 360V
nominal, 425V max DC input with a 550Arms maximum
phase current, 440Arms peak phase current and
300Amps continuous. The larger WTI-S260 – for bus or
large off-road vehicles – offers a 650V nominal, 800V max
DC input with a 600Arms maximum phase current,
475Arms peak phase current and 300Amps continuous.
The WTI-D260 is a dual inverter with two WTI-S260
The Curtiss-Wright
WTI inverters
output stages and an input stage - and provides
the extra peak torque that is required to launch large
vehicles, including articulated buses.
Currently under development, the WTI-S530 will
double the power of the WTI-S260, providing over
1000kW of maximum power for very large vehicles
including mining trucks.
Flexibility
To solve the potential issue of creating hardware and
software that wouldn’t support customer’s goals, the
engineering team developed the interface board
allowing additional circuits to be added for further
features. Thanks to its high-speed bus, the controller
board can support high levels of functionality, and
a new version of the interface board can be developed
and validated independently so the main inverter
isn’t modified. This means that to customize the inverter
hardware Curtiss-Wright can simply ‘re-spin’ a version
of the interface board, which saves both cost and time
to market.
Efficiency
The WTI-S260 realizes an efficiency of over 98% with
230Amps phase current and 10kHz switching frequency.
Even at 400A and 10kHz, the efficiency is 97%.
Curtiss-Wright achieves this with good control of the
gate and the type of insulated-gate bipolar transistor
(IGBT) that gives more current and lower losses.
The WTI-S260 has been designed for a very
long and high-power cycle life which, with its
rated peak current of 475Arms, is two million
power cycles or, at 500Arms peak drive cycle,
200,000hrs.
Safety and protection
ISO26262 Functional Safety was a strong consideration
for the WTI, with Curtiss-Wright incorporating
a dual-core lockstep processor, significant redundancy
and software plausibility checks should an OEM
want to go through the process of attaining
a system level rating.
WTIs also have unrivalled fault protection. In fact, the
only way to damage one is to give it too much voltage.
The WTIs superior short-circuit protection is able to
withstand a phase short under any impedance
condition. During a short, the condition is caught rapidly
and shutdown before damage can occur.
Adaptive control
Curtiss-Wright’s state-of-the-art, adaptive motor control
software dynamically adjusts motor tables to optimize
performance. This increases power and stability in the
higher speed constant power region of the motor
torque - speed curve, which achieves power gains of
between 15% and 38% depending on the motor.
Adaptive control also ensures stable performance at
up to 4.5X the base speed of a permanent magnet (PM)
motor, something not seen in any other control routine,
which means the vehicle can still hit top speed even at
a low battery state of charge.
Integration features
The WTI uses the latest high voltage connectors, which
are fast to connect, improve the Takt time of the line and
ensure the ability to drive a motor through up to
11 meters of cable. This greatly increases the OEMs
options when deciding where to site the inverter on
their on- or off-highway vehicle.
Communication is via the J1939 CAN protocol, with
the physical layer being ISO11898-2 compliant with
support for ISO11898-1 CAN variants. iVT
Author: Chris Howe, marketing manager, Curtiss-Wright
Successful inversion
/pivt
/iVTInternational.com
