Employing DC transmission in long distance AC motor drives: Analysis of the copper economy and power losses reduction in mining facilities

High-frequency problems related to PWM motor drive systems with long cables are widely discussed in the literature and are very harmful to the system components, resulting in motor insulation failures, bearing damage and electromagnetic interference, among others. As a solution, it was proposed in a previous work an alternative system configuration, in which the rectifier and the inverter are separated through a long DC cable, being the inverter located at the motor terminals. Thus, besides the reduction of all these problems, the proposed topology also presents the additional benefit of reducing the amount of copper required in the power transmission and the cable power losses as well. In this context, this paper aims to carry out a complete evaluation on the copper economy obtained through this alternative drive configuration, as well as presenting a case study involving real motor drive systems situated in mining plants, in which the actual cost of the cables is compared with that on the alternative configuration.