NCEES Sample Power Problem #522 Question

[ndekens]

#522

A Power Plant uses a turbine driven synchronous generato rated 3-Phase, 150MVA, 13.8KV, 0.85 Lagging PF.

At rated conditions the Real Power output (MW) is most nearly:.......

I calculated as follows:

150MVA * 0.85PF * 1.73(for 3-Phase system) = 220 MW

However the book seems to answer the problem as if it was a single phase system as follows:

150MVA * 0.85PF = 127.5 MW

Now hear is my question why not multiply by Sqrt 3? By using the Sqrt 3 am I calculating Apparent Power instead of real power?

 

[Flyer_PE]

If not stated specifically, the power rating given for a generator will be the total output. You are only dealing directly with power values. Sqrt 3 is only a factor when you are dealing with phase voltages and currents.