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Unformatted text preview: is also constant for these cases. 4) A 1500 v, 3-phase synchronous motor is driving a pump. The field has an adjustable rheostat and the stator windings have ammeters to monitor current. When the rheostat is adjusted so that the ac line current is a minimum, the ammeter indicates 5A. a) What horsepower is being delivered to the pump (neglect losses)? b) How should the rheostat be adjusted so that the motor is operating at .8 power factor leading? c) What is the reactive power being supplied to the system at .8 power factor leading? 4) The field current of a synchronous motor is increased, causing the line current to decrease. Was the machine operating at leading, lagging, or unity power factor before the change? L q L d L s = = E as I s ei ss ( 29 ( 29 cos I fd ss ( 29 sin...
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- Fall '09