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Calculating the Line Current and Power Factor for Synchronous Motor Connected to a Pump

J14-Q6, J15-Q6, J17-Q6, J22-Q2


A three-phase 6600 V feeder supplies power exclusively to a pump station consisting of a number of pumps and motor units. When all the original pump and motor units operate simultaneously, the feeder carries a load of 1000 kVA at a power factor of 0,8 lagging.


An additional 600 kVA-synchronous motor is installed in the pump station to drive an extra pump. When run unloaded, this motor absorbs 60 kW. The pump to be powered by the synchronous motor requires 270 kW to drive it. When delivering 270 kW, the motor is 90% efficient.


1. Calculate when ALL the original pumps are in operation and the synchronous motor is driving its pump:

1.1. The line current in the feeder [10]

1.2. The power factor of the feeder at the pump station [1]


2. Determine when ALL original pumps are in operation, and the synchronous motor is uncoupled from its pump and run unloaded:

2.1. The line current in the feeder [8]

2.2. The power factor of the feeder at the pump station [1]




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