Diesel-electric drive has several advantages over traditional mechanical drive, and in large construction vehicles, those advantages can be exponential. Terex Unit Rig has developed a new ac-drive dump truck, the MT6300AC, for the mining market that it claims is one of the largest and most efficient available. Terex says that it is the only 400-ton (363-t) truck offered designed from scratch.
The MT6300 is fitted with a 20-cylinder MTU Detroit Diesel C3 Series 20V4000 engine that provides 3750 hp (2800 kW) for applications specific to the mining industry. To endure hot and dusty conditions, it is equipped with multiple oil-filtration systems to maximize oil life as well as a 6.5-ft (2-m) cooling fan. The engine also meets strict U.S. EPA requirements by using a L'Orange common-rail-injection system with an injection pressure of 20,305 psi (1400 bar), and a multistage crankcase ventilation system supplied by Hengst Filterwerke.
Power is sent via an IGBT (insulated-gate bipolar transistor) to the rear ac-drive electric motors, each having a gear ratio between 32:1 to 42:1. The new triple-reduction ac drive is able to provide the maximum tractive effort, even when fully loaded in difficult conditions such as oil sands.
For traversing slopes, the ac-drive system can quickly change from a full propel to a full retard scenario. Braking is otherwise hydraulic but with multiple systems for enhanced safety. A retarding force of 6000 hp (4476 kW) is available and, by using ac drive, enables full retarding power to be used until the truck stops.
Rough mining roads can cause problems for smaller and lower trucks, but the MT6300 has a front axle ground clearance of 36 in (914 mm) and another 1 in (25 mm) more at the rear when fully loaded. The 520,000-lb (235,868-kg) truck has a top speed of 40 mph (64 km/h).
Terex says the body was built specifically for the truck's 400-ton capacity. Oil-sand mining companies are large purchasers of such vehicles, but transporting the dense ore for refining causes some issues. The MT6300 has a curved bed floor, front, and canopy to enable complete dumping of the loads and can be ordered with a bed-heating option, helpful when unloading non-viscous material. The bed also includes runners that spread load weight to the frame as well as joint isolation to reinforce welded areas.
The driver sits high above the ground in a newly designed cab with 191° views, protected by a structure meeting all ROPS (roll-over-protective structure) and FOPS (falling-object-protective structure) standards. The 82 dB(A) interior features CAN gauges, power windows, and pressurized and filtered air.