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Watts and vars – Measurement Computing WavePort 312P rev.1.0 User Manual

Page 82

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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

]