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MINExpo 2016 Review: underground

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World Coal,

Heading underground, Caterpillar premiered its new Cat HTD4100 high torque drive system for longwall armoured face conveyors (AFCs) at MINExpo 2016 in Las Vegas.

The system consists of two main components: a variable frequency converter and the motor-gearbox combination. In the new Cat system, a medium voltage converter-controlled torque motor replaces the AC induction motor. The control principle of the drive is direct torque control: the most advanced AC-drive control technology available, according to the company.

The converter-controlled torque motor operates at low speeds of between 0 and 300 rpm versus 1500 rpm for induction motors. Lower speed reduces inertia acting on the output shaft by a factor of eight and enables the system to react quickly, which translates to little or no damage to the gearbox and chain in the event of a conveyor blockage.

The installed motor power of the modular drive system is 1250 kW (1900 hp at 60 Hz) with maximum torque of 650 000 Nm (480 000 lb-ft). The torque motor design reduces the need for as many gear stages, which enables the entire system to be simplified. This in turn allows smaller dimensions, while retaining the same torque capabilities as systems that are as much as 20% larger. The smaller size allows flexibility in laying out longwall entries.

Caterpillar will be able to configure the high-torque drive system for retrofitting to existing longwall face conveyors. Plans call for supplying a range of high torque drive systems to handle voltages of 3.3 kV or 4.16 kV in a mechanical power range of 300 kW to 1600 kW (400 hp to 2100 hp). Systems for additional applications, such as longwall plough systems and beam stage loaders, will follow. The system will start field trials in 2017.

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