February 6th, 2019, 05:53 AM  #1 
Member Joined: Feb 2018 From: England Posts: 60 Thanks: 0  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 06:19 AM. 
February 6th, 2019, 06:17 AM  #2 
Global Moderator Joined: Dec 2006 Posts: 20,298 Thanks: 1971 
A 3phase 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.

February 6th, 2019, 09:12 AM  #3 
Banned Camp Joined: Mar 2015 From: New Jersey Posts: 1,720 Thanks: 124 
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 online. 
February 6th, 2019, 09:48 AM  #4 
Member Joined: Feb 2018 From: England Posts: 60 Thanks: 0 
Hi Skipjack, What is the correct way to perform this calculation? 
February 6th, 2019, 12:58 PM  #5 
Global Moderator Joined: Dec 2006 Posts: 20,298 Thanks: 1971 
The question doesn't really make sense, but calculating 2.16 MW, as I suggested, seems to be all that you can do.

February 7th, 2019, 09:25 AM  #6 
Banned Camp Joined: Mar 2015 From: New Jersey Posts: 1,720 Thanks: 124 
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. 

Tags 
phase, power, system, total 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Pointwise, total convergence, and sum of a (power?) sequence  Awild  Calculus  3  October 5th, 2017 02:34 PM 
phase plot  question  Physics  3  May 12th, 2012 01:41 PM 
phase diagrams  osem  Math Software  0  November 17th, 2010 05:46 AM 
Phase portrait of a differential system  Seng Peter Thao  Differential Equations  0  June 30th, 2007 11:56 AM 
phase plot  question  Algebra  2  December 31st, 1969 04:00 PM 