Modeling and Evaluation of Cycloconverter-Fed Two-Stator-Winding SAG Mill Drive-Part I: Modeling Options

Typical drive configurations of high-capacity SAG mills use a two-stator-winding vector-controlled synchronous motor, with a 30 degrees shift between the two windings, fed by a two-secondary delta-delta-wye power transformer and two six-pulse cycloconverters. This paper presents and evaluates three different modeling options for the SAG mill drive. The first option considers a complete model in phase and qd0 variables of the two-stator-winding synchronous motor fed by two six-pulse cycloconverters. The second option develops a winding rotation transformation to obtain an equivalent one-stator-winding synchronous motor, which is fed by a 12-pulse cycloconverter. The third model considers the equivalent one-stator synchronous motor fed by an ideal converter that produces purely sinusoidal voltage and current waveforms. Each model is evaluated during steady state, step speed commands, and step load disturbances. Responses are compared to field records of an 8.2-MW SAG mill, confirming the accuracy of the developed models.