Developing the Drive System for the World`s Largest Haul

EMJ_pg76-77_EMJ_pg76-77 10/31/13 9:47 AM Page 76
HAUL TRUCKS
Developing the Drive System for the
World’s Largest Haul Truck
System designers discuss the drive technology BelAZ will use to propel its 500-ton truck
By Steve Fiscor, Editor-in-Chief
Economies of scale are vital, especially when mining bulk
commodities such as coal and iron ore. During early October,
a surface mining equipment supplier based in Belarus will
commission the largest haul truck ever built. The new BelAZ
500-ton haul truck has already pushed the envelope for
ultra-class haul truck design. Building a vehicle with a 450metric ton (mt) payload capacity is one thing. Developing the
power plant to effectively propel the payload along with the
weight of the truck (360 mt) up a ramp fully loaded is an
engineering feat.
The new BelAZ truck is powered by advanced AC systems
developed by Siemens. At Mining Media’s 2013 Haulage &
Loading conference, which was held during May in Phoenix,
representatives from Siemens with permission from BelAZ
discussed the truck’s electrical drive system. Siemens has
been developing drive systems for haul trucks for about 15
years, explained Walter Koellner, senior director-mobile mining, Siemens.
“Our first electrical drive system for haul trucks was
based on GTO technology working with Liebherr and
Hitachi,” Koellner said. “In 2005, we began using IGBTs. In
2007, we introduced a trolley system for the IGBT system.
We have built systems to propel 240- to 400-ton haul trucks.
Last year, we introduced a combination of the electrical drive
and a mechanical spindle. It is installed on a haul truck in
China. This year… our next big achievement is the largest
truck in the world—the electric drive system we are building
for BelAZ.”
The open-pit mining sector has debated whether bigger is
better at every stage throughout history. At different points
The BelAZ 500-mt haul truck is similar in width and height to competing ultra-class
haulers, but longer.
76 E&MJ • OCTOBER 2013
along that timeline, the size of the trucks pushed shovel
makers to build bigger units and vice versa. Today, the industry has reached a point where the largest shovels have capacities of 135 tons, which has placed the onus on the truck
makers to make the next move to properly match 3- to 4pass loading scenarios.
The 500-ton BelAZ is noticeably different than current
ultra class haulers. The rig stands 26-ft high and it is 32-ft
wide and 67-ft long. Roughly the same width and height, but
quite a bit longer than the Komatsu 930E or Cat 797, which
are roughly 50-ft long. The truck has two axles and eight
tires. The drive system consists of two 2,500-hp engines
with two alternators driven by each engine. One electrical
cabinet controls the inverters and motors. There are four
wheel motors.
When BelAZ first presented its idea, Dr. Joy Mazumdar,
business manager-mining trucks, Siemens, recalled thinking,
“OK…. How are we going to make this thing run electrically?
We had an aggressive schedule in bringing this truck to market,” Mazumdar said. “We assessed our options. We needed
motors that could drive the system and a suitable control system for this application. We also needed a proper cooling system and braking mechanism.”
Siemens had plenty of experience working with haul truck
payloads from 240 tons to 400 tons. The first thought with
500 tons was, let’s just double a 240-ton drive system,
Mazumdar said. “That seemed like a fairly straight-forward
solution, but the amount of real estate on the truck is limited. We needed to fit more power in a finite space.”
The next approach looked at the 400-ton drive system and
the engineers wondered if they could extend the system to
handle 500 tons. “The limiting factor was finding the proper power devices as far as semiconductor technology,”
Mazumdar said. “Over the years, payloads were increased
substantially through the use of IGBTs. We developed a concept, but the devices weren’t available in the market yet. So,
while we were working on the software for the drive system in
Atlanta, our colleagues in Nuremberg, Germany, were developing the semiconductor technology.”
When it came to the motors, Siemens opted for the
240-ton concept. “All four wheels will have independent
motors driven by two alternators with two engines,”
Mazumdar said. “That concept is similar to the two times
240-ton truck. When it came to the controls, however, we
decided to a use a 400-ton control system, replacing the
IGBTs with higher current devices. We needed more current
in the same footprint.”
Creating a hybrid system, the Siemens engineers took a
400-ton inverter system and merged it with a 240-ton,
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HAUL TRUCKS
Conceptual illustration of the world’s first 500-mt capacity truck.
motors-alternator arrangement and developed a solution to
drive a 500-ton truck.
“For the gridbox, we modified the 400-ton system for
500 tons and the cooling system is similar to the 240-ton
system, placed on two separate axles,” Mazumdar said.
“Theoretically, this system would work. The Siemens engineering team then tested the concept through calculated
simulations to determine the truck’s performance.
The Siemens AC haul truck platform is 1,800-volt DC
link. The rated voltage is 1,300 to 1,400 volts. The four
new inverters they developed (one for each wheel) were
IGBTs rated at 1,500 amps, 3,300 volts. The traditional
version was 1,200 amps, 3,300 volts. “The increased amperage made it possible to use the same inverter skid,
but allowed more current for the increased torque,”
Mazumdar said. “This enabled the solution. Looking at
pictures or drawings, the inverter system looks identical to a
400-ton system.”
There were several modifications to the electrical cabinet.
Two alternators required more space. There are also two field
exciters and extra rectifiers, but all of the additional components could fit into the existing skid.
Siemens uses electrical retarding on all of its trucks with
IGBT choppers. The gridbox is similar to a 400-ton system,
but it had to be extended to 24 resistors for modularity.
Earlier versions have 20. “This truck will not roll backward
down grade,” Mazumdar said. “There is no slippage.”
The traction control system has independent control for
all four wheels. “That’s a question of coordination,”
Mazumdar said. “It has to coordinate the four wheels, two
alternators and two engines. It has to have mine grade
robustness and at the same time be able to operate in ‘limp’
mode if an alternator or engine goes down.”
The new 500-ton BelAZ truck is expected to be able to
travel up a 10% grade with 2% rolling resistance with a
speed of 11 km/hr. During retard, it could safely travel downhill at 30 km/hr. Short time braking requires 6 megawatts
(MW), regular braking is 5.3 MW. The gear ratio is 29.5.
Siemens has successfully developed a system for BelAZ
that allowed them to power a 500-ton truck with the same
footprint as a 360-ton truck, which simplified the design of
the truck’s power deck layout. E&MJ will have a correspondent at the factory in October and carry a full profile in the
November edition as the first unit heads to work at a Kuzbass
coal operation in Siberia.
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OCTOBER 2013 • E&MJ 77