Homework Help: Phase Power Calculation

1. Jan 15, 2016

TurboST2

1. The problem statement, all variables and given/known data
I need to calculate the power for phase A, B, and C so that I can determine the total power into the system.

I have measured the following data:
VA magnitude = 117.7 [v]
VA angle = 0°
IA magnitude = 7.5 [A]
IA angle = -25.5°
VB magnitude = 117.7 [v]
VB angle = -124.1°
IB magnitude = 7.7 [A]
IB angle = -145.7°
VC magnitude = 117.2 [v]
VC angle = 117.5°
IC magnitude = 7.3 [A]
IC angle = 94.8°

2. Relevant equations
P=IV

3. The attempt at a solution
Does this mean?:
Phase A power = 882.75 [w]
Phase B power = 906.29 [w]
Phase C power = 855.56 [w]

Total power into system = 2644.6 [w]

2. Jan 15, 2016

Staff: Mentor

Hi TurboST2

So you didn't take phase angle into account? That means you've calculated volt-amps for each phase, not watts.

Does your textbook show a formula for AC power?

3. Jan 15, 2016

TurboST2

Thank you for the helpful reply. No I did not take the phase angle into account. I wasn't sure if this was necessary for calculating power in this way.

Taking the angle into account would I use this equation instead? P=VIcos(θv-θi) giving the following results:

Pa = 796.75 [w]
Pb = 842.64 [w]
Pc = 789.28 [w]

Ptotal = 2428.67 [w]

4. Jan 15, 2016

Staff: Mentor

If you showed the data you used in arriving at those new numbers, it would be easy to judge whether you are on the right track.