Increased productivity with AC drives for mining excavators and haul trucks

This paper reviews how the effective implementation of AC drive systems on mining excavators (shovels and draglines) and haul trucks has led to dramatic increases in productivity. The review focuses on the major factors that influence productivity: production rate; reliability; maintenance cost; power grid compatibility; system intelligence; and efficiency. Key features of the haul truck drive are powerful GTO technology and the ability to operate on overhead trolley lines at twice the power of existing haulers. Depending upon the truck's gross vehicle weight (GVW), the on-grade speed can increase by up to 80%. The system is designed for operation on 2600 V lines, but can also operate on existing 1600 V lines using a novel diesel boost mode. The drive system also features software for enhanced drivability, optimum engine control, and an electronic dash display. The key feature of the excavator drive is its active front end (AFE) technology, using 3.3 kV IGBTs, that achieves powerful dynamic performance, while providing exceptional compatibility with the line in terms of power factor and total harmonic distortion (THD). The shovel achieves current THD of 3.5% and the dragline 0.5%. The drive system also features a contextual maintenance system.