Caterpillar will begin producing electric-drive versions of its 150- to 400-ton, rigid-frame mining haul trucks, probably in late 2008. Caterpillar executives announced the move in late March at the company’s Tinaja Hills proving grounds and training facility near Tucson, Arizona.
Caterpillar experimented with electric-drive mining trucks as early as the mid-1960s, but ultimately opted to manufacture mechanical-drive mining trucks. “But we’ve kept track of the evolution of electric-drive technology over the years,” says Ed McCord, product manager, Caterpillar Global Mining. “And over the years, many of our mining customers have told us electric-drive trucks work better for them in some applications and that they want that option from Caterpillar.”
The move to electric-drive trucks is a logical one, McCord notes, because electric power generation is such a huge part of Caterpillar’s business today. “This means we will be able to offer mining customers a completely integrated electric-drive design built entirely of Caterpillar components and technology,” he continues. “Competitive electric-drive designs use modified locomotive components on a proprietary chassis. We believe this gives Cat an advantage because you can have great individual components assembled into a poor product if those components are not optimized, communicating and assembled in the correct way.”
Key to Cat’s plan is a partnership with Mitsubishi Electric. Mitsubishi will supply semi-conductors designed and built in conjunction with Caterpillar.
In another departure from industry standards, McCord says the new electric-drive trucks will operate on alternating current systems, as opposed to direct current electrical systems, which have been the norm since electric-drive trucks were first developed. “Mines are getting deeper,” McCord notes. “And alternating current drives allow trucks to make longer runs with higher payloads. In addition, AC drives give superior electric braking in severe downhill hauling applications and offer the potential for trolley operations [where the truck is powered via an overhead electric cable – similar to an urban trolley car].
The mining trucks will use Cat’s new C175 engine family with ACERT emissions control technology. The engines are available in 12-, 16- and 20-cylinder configurations with power ratings from 2,000 to 4,400 horsepower. The C175 engines replace Cat’s 3500 Series.
Currently Caterpillar is operating a Model 797 haul truck as a mobile test bed. “We removed the truck’s mechanical drive, installed the electric drive system and began testing in one week’s time,” McCord says. “We believe this is an industry record and a testimony to the success of our partnership with Mitsubishi.”
Current plans call for Cat to introduce its electric-drive system in two truck models over 200 tons at MineExpo in September 2008.