YOKOGAWA WT500 User Manual page 138

5.4 Setting the Equations for Apparent and Reactive Power
Explanation
5-12
Selecting an Apparent Power Equation
In normal measurement, apparent power is the product of voltage times current. You
can choose which normal measurement voltage function (Urms, Umean, Udc, Urmean)
and current function (Irms, Imean, Idc, Irmean) the WT500 will multiply to determine the
apparent power from one of the combinations below.
• Urms*Irms
The apparent power is determined from the product of the voltage and current true
rms values.
• Umean*Imean
The apparent power is determined from the product of the voltage and current rectified
mean values calibrated to the rms values.
• Udc*Idc
The apparent power is determined from the product of the voltage and current linear
averages.
• Umean*Irms
The apparent power is determined from the product of the voltage's rectified mean
value calibrated to the rms value and the current's true rms value.
• Urmean*Irmean
The apparent power is determined from the product of the voltage and current rectified
mean values.
Selecting an Apparent Power and Reactive Power Equation
You can choose the equation for apparent and reactive power from one of the following
three types. For details, see section 2.5.
• Type 1 (The method used in the normal mode of conventional WT series power
meters)
Active power for a three-phase, four-wire system
Apparent power for a three-phase, four-wire system
Reactive power for three-phase, four-wire system
• Type 2
Active power for a three-phase, four-wire system
Apparent power for a three-phase, four-wire system
Reactive power for a three-phase, four-wire system
• Type 3 (The method used in the harmonic measurement modes of the WT1600,
the PZ4000, and the WT3000)
This equation can be selected on models with the harmonic measurement option
if harmonic measurement is proceeding properly. For an explanation of harmonic
measurement, see chapter 6.
Active power for a three-phase, four-wire system
Apparent power for a three-phase, four-wire system
Reactive power for a three-phase, four-wire system
PΣ = P1 + P2 + P3
SΣ = S1 + S2 + S3
( = U1×I1 + U2 × I2 + U3 × I3)
QΣ = Q1 + Q2 + Q3
PΣ = P1 + P2 + P3
SΣ = S1 + S2 + S3
( = U1×I1 + U2 × I2 + U3 × I3)
QΣ= SΣ 2 -PΣ 2
PΣ = P1 + P2 + P3
SΣ= PΣ 2 +QΣ 2
QΣ = Q1 + Q2 + Q3
IM 760201-01E