Diesel and electric
technologies in partnership
58 iVTInternational.com November 2019
John Deere’s 944K
Hybrid Wheel Loader
uses two electric
generators to power its
four wheel motors
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JOHN DEERE POWER SYSTEMS
IN THE WORLD OF OFF-HIGHWAY VEHICLES WE SHOULDN’T LOOK AT DIESEL AND ELECTRIC
SOLUTIONS AS BEING IN COMPETITION, BUT INSTEAD AT HOW THEY CAN WORK TOGETHER
As more off-road market segments introduce
electrification technology, there’s buzz around
diesel versus electric solutions. However, in viable
electrification solutions for off-highway vehicles, it’s not
about which technology will eclipse the other — it’s
about where and how each technology will be applied.
While diesel power generation is here to stay, its role
may evolve. In a traditional sense, a diesel engine is used
to provide the torque to the axles to physically move the
vehicle. In a hybrid electric solution, it shifts to a power
generation source, providing the energy needed to
support the electric drive system.
Combining and reconfiguring
In a hybrid electric configuration, there’s an opportunity
to develop pure power generation for variable speed
generator sets, which would use battery packs as the
energy source and be supported by a variable speed
generator set.
In the traditional method of running a generator set,
the engine must run at a set speed to be utilized for
consumer power. It has to run at this speed at all times,
regardless of whether or not the load on the engine
matches the power output. This means that when the
load on the engine is small, it’s not running as efficiently
as it could and is generating excess power.
However, by placing a battery pack between the end
application and the engine generating the power, the
power electronics would instead provide the consumer
energy, acting as a buffer between how the power is
generated and when and how it’s used. Applications
would run off the battery power, which would get its
energy from the generator set engine.
Switching the role of the engine from generating
torque to generating power allows the power to be used
more efficiently — and only when it is required by the
load. This reduces fuel consumption, as the engine isn’t
running at high speeds when the power isn’t required. In
this scenario, the engine in a variable speed generator
set would turn on only when the battery’s energy level
drops below a certain point and needs to recharge.
Three electrification factors
This hybrid setup highlights the three main areas of
electrification: power generation, power conversion and
power usage. Optimizing how these three factors work
together is key to creating a robust, viable solution.
On the power conversion side, battery technology
will play an interesting role in how electrification
solutions evolve. Today, because of the power
requirements in off-highway applications, the number of
kilowatt hours needed from battery technology to
sustain operations for a full work cycle – combined with
the time it takes to charge those batteries – make it
challenging for off-highway applications to be fully
electric for the foreseeable future.
When it comes to how the power is used, there are
a wide variety of solutions. On the John Deere 944K
Hybrid Wheel Loader, two generators provide power to
its four-wheel motors. Driven by the engine-mounted
gear box, the generators convert mechanical energy
from the engine to electrical energy. This energy is then
transferred to the power electronics system, which
distributes the energy to the four-wheel motors
depending on operator commands.
The variety of applications in which electrification can
be applied presents an exciting opportunity. Solutions
can be custom-built to meet OEM needs. From a wheel
or process drive to turning a specific shaft or
implementing an electric power interface, there’s
a way to optimize the solution.
A range of experience
John Deere Power Systems has solutions in all three
areas of electrification: power generation, power
conversion and power usage. All can be built
in-house and therefore all the interfaces are engineered
to work together.
The company has experience integrating these
systems, meaning OEMs can have confidence this new
technology is designed to work on their machines. iVT
Author: Darren Almond, strategic marketing lead,
electrification, John Deere Power Systems
/iVTInternational.com
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