# 3 AND 1 PHASE POWER EQUATIONS:



## Redskinsdb21 (Feb 19, 2013)

FOR 3PHASE: P = v X I X PF X SQRT(3)

FOR 1PHASE P = V X I X PF

1) ARE THESE EQUATIONS CALCULATING POWER ABSORBED BY LOAD OR POWER SUPPLIED BY SOURCE?

2) Also, in the following equations:

P_phase = E_phase x I_phase x cos(theta).....the book says its the power dissipated in each phase of either a wye or delta connected load....does this mean power dissipated in conductors to the load? or power absorbed by the load from each phase? ...I am geting this one confused with P = v X I X PF X SQRT(3) and what the difference betwwen the 2


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## Wael (Feb 19, 2013)

1- it applies to both. for most problem you calculate this to find the Power consumption at Load side

2- PF= cos (Theta), E=V: so [P= VI PF] is same as [EI cos (theta)] ( given that you are dealing with phase values)

3 P in three phase= Vline x I line x Sqrt(3)

2 and 3 applies for Delta and Wye configurations

4-Power dessipated in conductor is ( I^2 R of conductor)


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## Peele1 (Feb 19, 2013)

Take any power system or component, draw a box around it, and you can calculate Power. Power generation, power loss due to transmission lines, power consumed. Whatever. I find it easiest to do all Power calculations in vector format.

*S* = *V* *I** SQRT(phases[1 | 3])

*V* = *I Z*


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## Redskinsdb21 (Feb 19, 2013)

Wael said:


> 1- it applies to both. for most problem you calculate this to find the Power consumption at Load side
> 
> 2- PF= cos (Theta), E=V: so [P= VI PF] is same as [EI cos (theta)] ( given that you are dealing with phase values)
> 
> ...


If p (3phase) = Vline x Iline x sqrt(3), how does S = Vline x Iline x sqrt(3)?


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## Wael (Feb 20, 2013)

Sorry, Seems i forgot to add the PF in P formula.

So: P in three phase= Vline x I line x Sqrt(3) x PF


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