A OPEN PIT MINING AÇIK OCAK MADENCİLİĞİ

A. Wood
hydraulics, couplings and gear units to the
diesel engine.
1.2 Electric Drive Wheel Loaders
Electric Drive Wheel loaders are found in
high production mining applications, mainly
as primary loading tools. The size and class
of this type of wheel loader starts at Joy
Global LeTourneau L-950, (25 Tonne
payload), and ranges up to the L-2350 (72
Tonne payload), which is twice the capacity
of the largest mechanical wheel loader, and
has comparative payload to 40m³ hydraulic
shovels, (PC8000, EX8000 class). (Fleet,
2012)
Figure 3. LeTourneau L-2350 Electric Drive
72 Tonne Wheel Loader.
1.2.1 Design Features
The most significant design feature of
electric drive wheel loaders is electric power
regeneration, which is captured and fully
reutilized. (Fleet, 2012)
The main drive diesel engine is coupled
directly to a generator, which provides the
electric power to operate the loader.
Each wheel is mounted on an individual
wheel driver assembly, consisting of a
planetary transmission and electric motor.
The loading cycle consists of propel to
bank, dig, reverse propel, propel to truck or
hopper, dump, and propel back to start of
cycle. At each point in propel, the loader
consumes fuel on acceleration, and at steady
state. However, on deceleration, which is
done through electromagnetic braking, the
wheel motors are used as generators, which
feed power back to the power control system.
Figure 4. Electric Drive Wheel Loader
Layout.
This regenerated power is used to drive
the generator, which is directly coupled to
both the diesel engine and the main hydraulic
system. As the regenerated power drives the
generator, there is no load on the diesel
engine, and fuel supply is cut off. This is the
basic design feature which significantly
reduces fuel consumption of this type of
loading tool.
Electromagnetic primary braking reduces
maintenance time and replacement costs
associated with mechanical disc brakes.
As the wheel loader has independent four
wheel drive, power and speed are controlled
to each wheel, which allows power to be
reduced to any individual wheel which starts
to slip, regaining traction. This prolongs tire
life through reduced wheel spin, and through
correct individual wheel speed when turning.
(Fleet, 2012)
An electric drive wheel loader can
continue to perform its function if one of the
wheel motors fails, allowing for reduced, but
continued production, and the ability to
propel back to the maintenance location,
under its own power, when replacement is
ready.
This system has stepless forward and
reverse propel, negating any need for
standard mechanical drive train. Fewer
mechanical parts allows for less maintenance
and higher availability than mechanical
based systems. This also allows for
significantly less consumption of lubrication
fluids, making it an altogether more
environmentally friendly tool.
Electric motors are brushless DC,
requiring no maintenance, other than bearing
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