
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
]
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