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 important 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.