DC power vs AC power for mobile mining equipment

This paper proposes the use of DC distribution systems in mining applications. In mining a considerable attention is paid to cost optimization per ton of material moved. Therefore, there is a continuous push to use more efficient machines and systems. Electric dragline is the largest excavating machine used in mining, with the least cost per ton and the highest productivity. Any improvement of their electrical system would result in a significant energy saving. On the other hand, DC distribution is an effective method of power delivery which offers a number of advantages including lower electric losses, integration of small distributed generation, better power quality and stability. In this paper, draglines are considered as a case study to verify feasibility of DC distribution systems, in both delivery to a dragline across the mine site and power distribution inside the dragline. Several scenarios are considered, showing the advantages of DC power distribution for DC-based draglines, AC-based draglines, and for effective transition from DC- to AC-based. It will be shown that 12-15% efficiency improvement can be achieved by using the DC distribution system. Moreover, there exist a clear potential for integration of renewable energy sources and energy storage devices, to further improve stability and energy efficiency.