Hybrids and electric-drive machines already on the market from high-profile manufacturers (Komatsu, Caterpillar, John Deere) have shown enough promise in fuel savings and productivity to offset the concerns some managers have about their higher acquisition costs—that realization means OEMs are far from finished bringing these units to customers.
Liebherr is preparing a new entry into the game with its T 236 off-highway mining truck, a 100-metric-ton diesel-electric drive rigid-frame dumper.
It features the company’s Litronic Plus Generation 2 AC Drive system with “Active Front End” technology that uses electrical energy during retarding events so the drive system delivers controlled engine speed with almost no fuel consumption, Liebherr says.
The Active Front End function of the alternator is driving the engine during retarding; during propel phases, the electric drive controls the powertrain.
Also, a variable hydraulic drive system is designed to lower machine parasitic losses to provide maximum power and lower fuel consumption when power is not required.
“The technology is allowing all the components to operate at peak efficiency independent of external conditions,” says Liebherr’s Dr. Burkhard Richthammer, managing director of design and engineering for the company’s mining equipment.
“The result is optimal engine operation in both propel and retard events, with a level of protection to the engine that mechanical drive cannot match.” Richthammer said users will be able to expect increased reliability, longer engine life, less tire wear, increased component life, and reduced fuel burn compared to mechanical trucks.
“That Active Front End function allows the engine friction to be used for retarding and provides power to the auxiliary drives, reducing fuel consumption and also ensuring the engine never overspeeds,” Richthammer says. “Almost no fuel is used going downhill.”
Richthammer details a number of features for serviceability and safety.
An inline electrical powertrain layout minimizes cable length and the IP 68-rated plug-and-drive power modules are maintenance free.
The alternator is remote mounted and connected to the splitter box with a drive shaft. The electrical control cabinets of the drive are in maintenance-free segregated modules. The power modules only control the drive, operating with 600 volts AC and 900 volts on the DC link to remain in a class of low tension, while all auxiliary systems are hydraulically driven—this allows regular electricians to work on the system. An additional benefit of the external power module grounding system in the powertrain and positive drive isolation is that it allows work to be done on the machine while the engine is running.
The T 236 comes standard with a double pole battery, starter motor, and hoist system isolators. In addition, the drive system inhibit is electrically interlocked to grounding devices for each plug-and-drive power module.
Having undergone an internal testing phase, the truck is now in a primary field test at the Erzberg Mine in Austria. Further “pre-series” machines will be sent to selected operations around the world to further validate the truck’s capabilities, Richthammer says.
The Erzberg rock and iron ore mine is a stern test for the truck. It’s active more than 330 days a year in continuous 24-hour operation. Climates vary from -4 F and snow to summer temperatures of 104 F in the pit. There are both uphill and downhill haul cycles, and a near constant variation of grades.
Liebherr gave no indication how long field testing will last before the T 236 is commercially available. The prototype was unveiled at Minexpo 2016 in Las Vegas.