Rectifier-to-Inverter Connection Through Long DC Cable—Part II: The Complete Copper Economy Characterization

High-frequency problems involving long cable PWM motor drive systems are well documented in the literature. Solutions based on passive filters are conventionally used to suppress these undesired phenomena that take place in such systems, but, in turn, bring up new considerations concerning filter size, weight, cost, and electrical losses. In this context, a concept of an alternative motor drive system that overcomes all these problems was outlined by the authors in a previous paper, where the long cable was used to connect the rectifier to the inverter, thus establishing a dc power transmission link. In addition, other important issues concerning the proposed system have also been adressed, along with a comprehensive analysis of the power losses in the (long) dc or ac cable and a preliminary estimation of the copper amount reduction in favor of dc transmission. In the present paper, the results from a more recent and general study for the complete copper economy characterization are presented, demonstrating that the proposed drive system configuration, aside from eliminating the whole high-frequency problem, is always advantageous also from the copper economy point of view.