Synchronous Machine Power Angle Confusion

AI Thread Summary
A synchronous machine with an armature voltage at a power angle of 120 degrees is operating as a generator because the excitation voltage (Ef) exceeds the terminal voltage (Vt). The power angle indicates the phase difference between the terminal voltage and the back EMF, which determines the direction of power flow. In this case, the machine is supplying power to the infinite bus. To calculate power transfer and power factor, the finite impedance in the connection must be considered, as it affects the overall power flow. Understanding these parameters is crucial for solving the homework problem accurately.
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<B>General Power angle question</B>

If I have a synchronous machine that has an armature voltage with a power angle of 120 degrees, is the machine operating as a motor or a generator and why? I have found conflicting answers to this question and need to straighten this up. For my homework problem, it is a 3-phase 1MVA, 2300V, 60Hz and Xs=0.9pu negligible stator resistance, and connected to an infinite bus. Vt=2300 at 0degrees and Ef=3450 at 120 degrees. Any help would be appreciated. I need to determine the power transfer and power factor and to do this I need to know how the machine is operating.
 
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Connected to an infinite bus via what? You need a finite impedance. The simplified power flow equation is ##P=\frac{V1V2}{x}sin(\theta)##
 

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