Measurement Computing WavePort 312P rev.1.0 - Manual (Page 82)

Glossary
11-6 Glossary PowerVista/312 User’s Manual
Watts and Vars
Fundamental Watts and Vars are defined from pre-calculated voltage and current vectors via the power
equation. In the equation below, S, V and I are complex vectors while P and Q are scalars.
S
60
= P
60
+ jQ
60
= V
60 ••••
I
60
*
RMS Watts and Vars are defined from the power equation as well. Vrms and Irms below are pre-calculated
magnitudes, and magnitude of complex power is on the left. S is termed volt-amperes, VA or KVA or MVA.
S
RMS
= V
RMS
•••• I
RMS
To determine RMS Watts and Vars, we need either P
rms
or Q
rms
. It is known that average power is also RMS
power or:
P
AVE
= P
RMS
Given that P
ave
is pre-calculated, RMS vars can be determined from:
Q
RMS
= SQRT[ S
RMS
 2 - P
AVE
2 ]