Complex Imaginary Test 2 Problem 21

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gEEk2007

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Question:

A balanced 3-phase, Delta connected synchronous generator with a power factor of .88 has a rating of 4.8 kV and 750 kVA. What is the real power output per-phase?

Answer:

Use the power factor to convert the kVA rating to real power. Then divide the real power by 3 to get the per-phase output.

Real Power (P) = 660 kW

P/3 = 220 kW / phase.

You would divide three phase kV by the square root of 3 to get single phase voltage.

Why do you divide by 3 and not the Square root of 3 to get the per-phase kW??

Thank you!

 
No, on a delta system, the phase voltage = the line voltage..

The total KW is 660 Watts, so with three phases, you just divide the total power by 3, and you get the per-phase KW.

 
Real power is Watts, so 750 KVA * .88 pf = 660 Watts (3 phase)

660/3 = 220 Watts single phase.

 
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