ELECTRICAL ENGINEERING DEPARTMENT
California Polytechnic State University
EE 255 Assignment #9
Problem #1
A 480V, 60Hz, 4pole, Yconnected synchronous generator rated at 470KVA and 0.85 PF lagging. Its
armature resistance is 0.016
.
Ω
The core losses of this machine at rated conditions are 7 KW, and the
friction and windage losses are 8 KW.
A.
Determine the electrical losses of this generator at rated conditions (stator copper losses).
B.
If this generator is operating at the rated conditions, what input torque must be applied to the shaft?
Express your answer both in Newtonmeters and in pound feet.
Problem #2
A 480V, 60Hz, 4pole synchronous motor draws 50 A from the line at unity power factor and full load.
Assuming that the motor is lossless, answer the following questions:
a.
What is the output torque of this motor? Express the answer both in Newtonmeters and in pound
feet
b.
What must be done to change the power factor to 0.8 leading? Explain your answer using phasor
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 Fall '11
 AliShaban
 Electrical Engineering, Electric motor, Power factor, armature resistance, newtonmeters

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