Oscillation Studies on Replacement of Phase–Wound Induction Motors of a SAG Mill Drive with Permanent Magnet Synchronous Motors

Abstract

The primary objective of every industry is to optimise production at preferably lower costs. These industries make use of electric motors for their operations and the mining industry is no exception. Often is the notion to replace the Semi-Autogenous (SAG) mill drive phase-wound induction motor with an equivalent synchronous motor. This paper evaluated the correctness or otherwise of the motor replacement from the point of view of oscillations. The SAG mill drive motor was modelled and simulated using Matlab/Simulink software to ascertain the level of oscillation at start and in running mode. Both motors gave same responses at an average load of 291.385 tonnes, where they delivered same power, speed and drew the same amount of current. At maximum load of 328.571 tonnes, the Permanent Magnet Synchronous Motor (PMSM) delivered more electrical power than the PWIM, both motors exhibited a constant speed characteristic and the current drawn by the Phase-Wound Induction Motor (PWIM) was higher than that of the PMSM resulting in additional power draw of value 208.3 kW. Oscillations of the PMSM on the whole were better than those of the PWIM. The PWIM is subject toreplacement in SAG mill drive systems.