Calculate Power Using RMS Voltage & Current

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SUMMARY

The discussion focuses on calculating total power using RMS voltage and current values in a three-phase system. The measured RMS values include a line-to-line voltage of 208 V, with individual phase voltages (VA, VB, VC) of 119.9 V, 119.5 V, and 119.2 V, and corresponding currents (IA, IB, IC) of 12.1 A, 12.2 A, and 12 A. The total power (Ptotal) is calculated as 4339.09 W, derived from the sum of individual phase powers (PA, PB, PC). The importance of phase angles in power calculations is also highlighted.

PREREQUISITES
  • Understanding of RMS voltage and current concepts
  • Familiarity with three-phase power calculations
  • Knowledge of power factor and its significance
  • Proficiency in using trigonometric functions for phase angle calculations
NEXT STEPS
  • Study the implications of phase angles in power factor calculations
  • Learn about three-phase power measurement techniques
  • Explore the use of power analyzers for accurate RMS measurements
  • Investigate the impact of harmonics on power calculations in AC systems
USEFUL FOR

Electrical engineers, students studying power systems, and professionals involved in energy management and electrical design will benefit from this discussion.

TurboST2
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Homework Statement


I need to calculate the power given the RMS values for voltage and current.

208 V line to line was put into the system. I measured the following data:

VA magnitude (v) = 119.9
VA angle (degrees) = 0
IA magnitude (A) = 12.1
IA angle (degrees) = -48.4

VB magnitude (v) = 119.5
VB angle (degrees) = -124.4
IB magnitude (A) = 12.2
IB angle (degrees) = -167.7

VC magnitude (v) = 119.2
VC angle (degrees) = 117.3
IC magnitude (A) = 12
IC angle (degrees) = 72.2

I believe the VA and IA values are the RMS values for voltage and current. I was given that VAN (rms) is about 120 (V) which is what was measured for the VA magnitude.

I need to fill out the table shown below.
mt5xyd.jpg

α, VA'N, VB'N and VC'N can be ignored, I have the values for those columns.

Homework Equations


PA = VA*IA
Ptotal = PA + PB + PC

The Attempt at a Solution



This is what I think the answer is for each column and how I got it
IA = 12.1 (A) from measured data
VAN = 119.9 (V) from measured data
PA = VA*IA = 119.9*12.1 = 1450.79 (w)

IB = 12.2 (A) from measured data
VBN = 119.5 (V) from measured data
PB = VB*IB = 119.5*12.2 = 1457.9 (w)

IC = 12 (A) from measured data
VCN = 119.2 from measured data
PC = 1430.4 (w)

Therefore, Ptotal = PA + PB + PC = 1450.79 + 1457.9 + 1430.4 = 4339.09 (w)
 
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Can you think of a reason why the phase angles of the each value might be important?
 
TurboST2 said:
This is what I think the answer is for each column and how I got it
IA = 12.1 (A) from measured data
VAN = 119.9 (V) from measured data
PA = VA*IA = 119.9*12.1 = 1450.79 (w)
This is so similar to your earlier thread that you could have continued in that same thread. The formula for 3 phase power remains the same.
 

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