Evaluating a New Configuration for Medium-Voltage Drive Systems in a Mining Plant

Large AC motors are ubiquitous in the mining industry, and these often require medium-voltage (MV) converters. Generally, long cables provide the connection between the variable speed drive (VSD) and the motor, which increases problems involving high frequency currents and overvoltages. These undesired phenomena are attenuated by large, heavy and expensive inverter output filters. As an alternative solution to such problems, the authors have proposed, in previous works, the separation of the frequency converter into its rectifier and inverter units, where the rectifier remains in its original location and the inverter is placed beside the motor, thus establishing a DC transmission link through the long cable. Such a configuration naturally (i) mitigates the high-frequency phenomena, (ii) reduces the voltage drop along the cable, and (Hi) can result in substantial copper savings. Until the present moment, the evaluations performed on the proposed topology was aimed at low voltage mining applications, which have shown excellent results. However, since MV drive systems are common in the mining industry, the proposed drive topology should also be analyzed considering this application. In this way, this paper evaluates the copper and energy savings obtained through this alternative drive topology by means of a case study involving three MV motor drive systems situated in a mining plant.