A coal mining “drag-line” machine in an open-pit mine consumes 0.92 MVA at 0.8 power-factor lagging ‘t hen it digs coal, and it generates (delivers to the electric system) 0.10 MVA at 1.5 power-factor leading when the loaded shovel swings away from the pit wall. At the end of the “dig” period the change in supply current magnitude can cause tripping of a protective relay, which is constructed of solid-state circuitry. Therefore, it is desired to minimize the change in current magnitude. Consider the placement of capacitors at the machine terminals and find the amount of capacitive correction (in kvar) to eliminate the change in steady-state current magnitude. The machine is energized from a 36.5 kV, three-phase supply.
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A coal mining “drag-line” machine in an open-pit mine consumes 0.92 MVA at 0.8… 1 answer below »