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February 6th, 2019, 04:53 AM   #1
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Total Power in 3 phase system.

Hi All,

How do I calculate the total power by a 3 phase electrical supply when the rms input voltage = 350v? The power is delivered along a wire with a resistance of 0.170 ohm.

Am I correct in saying V^2 / R = P
= 720588.2353.

MW megawatts answer.

Any help would be much appreciated.

Last edited by skipjack; February 6th, 2019 at 05:19 AM.
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February 6th, 2019, 05:17 AM   #2
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A 3-phase supply would be delivered via 3 transmission wires - one for each phase. Hence the wording of the question is a bit confusing. Multiplying your figure by 3 would give 2.16 MW after rounding to 3 significant figures.
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February 6th, 2019, 08:12 AM   #3
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If the voltage drop were 350 the voltage at the end of the line would be zero and the entire output of the power plant would be consumed in the line.

I don't know how to do it. Couldn't find it in old EE book or on-line.
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February 6th, 2019, 08:48 AM   #4
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Hi Skipjack,

What is the correct way to perform this calculation?
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February 6th, 2019, 11:58 AM   #5
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The question doesn't really make sense, but calculating 2.16 MW, as I suggested, seems to be all that you can do.
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February 7th, 2019, 08:25 AM   #6
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I have a generator with 120v at the terminals. Two 10ft wires leading from the generator are open at the ends, ie, the voltage across the ends is also 120v. The wires have a resistance of .170 ohms.

Is the total power V^2/r?

Power loss due to resistance in a supply line is an i^2r loss.
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