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A locked charge drop incident in a ball or sag mill is a catastrophic failure that causes high repair costs and loss of production. The locked charge event also produces high currents and torque demands, which can cause the drive or transformer overcurrent relays trip the mill motor.
Mineral grinding is one of the most important and critical stages in copper mining. Economy-scale has motivated the use of high capacity semi-autogenous (SAG) mill units whose continuous operation is essential to mine profitability. Hence, the development of modeling tools of SAG mill drive systems that help to analyze and prevent costly longtime outages, are of great benefit. Paper presents the development...
One very important charge condition that can produce a catastrophic failure during the starting of grinding mills is the compacting of the load inside the mill, especially after long downtimes. This condition is usually named frozen load and the load remains locked to the mill shell and after a half turn drops damaging the mill body and bearings. Therefore, the mill protection system must give an...
Typical drive configurations of high-capacity SAG mills uses a two-stator windings vector controlled synchronous motor, with 30º shift between the two windings, fed by a two secondary's delta-delta-wye power transformer and two 6-pulse cycloconverters. Paper presents and evaluates three different modeling options for the SAG mill drive. First option considers a complete model in phase and qd0 variables...
A detailed evaluation of a SAG mill starting is presented using three different modeling options. First option considers a qd0 model of the two-stator windings synchronous motor fed by two 6-pulse cycloconverters. The second option considers the qd0 model of an equivalent one-stator winding synchronous motor fed by a 12-pulse cycloconverter. And third option considers the equivalent one-stator winding...
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