Regenerative drives in the megawatt range for high-performance downhill belt conveyors

Downhill transport of ore from the mine to the beneficiation plant by means of belt conveyors introduces import-ant advantages both for the personnel and for the equipment. Furthermore, if the conveyor is equipped with a regenerative ac drive, the system will generate an important amount of electrical energy for use in the process. This paper discusses the technical alternatives and the criteria used to select a solution, using modern converter-inverter drives in the megawatt and medium-voltage range. The considered drive alternatives are: 1) an ac wound-rotor induction motor drive with additional resistors; 2) an ac synchronous motor with cycloconverter; 3) an ac induction motor with current-source inverter; and 4) an induction motor with multilevel voltage-source inverter. The study reveals that, considering the main technical criteria, the use of a three-level active front end feeding a voltage-source three-level inverter is the most appropriate alternative.