YOKOGAWA WT332 User Manual page 110

7.4 Features
7.4.2 Frequency Measurement
Item
Measured item
Method
Frequency measuring range Varies depending on the data update interval (see description given later) as follows:
Measurement range
Frequency filter
Accuracy
7.4.3 Computation
Item
Computing equation of apparent power (S), reactive power (Q), power factor (λ), and phase angle (Φ)
i : Input element number
UΣ[V]
IΣ[A]
PΣ[W]
SΣ[VA] Si=Ui×Ii
QΣ[var]
Qi= S −
2
i
λΣ λi = Pi/Si
Φ[°]
Φi = cos
• On the WT300 series, S, Q, λ, and Φ are derived through the computation of the measured values of voltage, current, and
active power. Therefore, for distorted signal input, the value obtained on the WT300 series may differ from that obtained on
other instruments that use a different method.
• If the voltage or current is less than 0.5% (less than or equal to 1% if the crest factor is set to 6) of the rated range, zero is
displayed for S or Q, and error is displayed for λ and Φ.
• For Q[var], when the current leads the voltage, the Q value is displayed as a negative value; when the current lags the voltage,
the Q value is displayed as a positive value. The value of QΣ may be negative, because it is calculated from the Q of each
element with the signs included.
7-10
Specifications
Voltage and current frequencies applied to the selected input element can be measured.
WT332 (two element model)
Select voltage (U1)/current (I1) of input element 1 or voltage (U3)/current (I3) of input element 3.
WT333 (three element model)
Select voltage (U1)/current (I1) of input element 1, voltage (U2)/current (I2) of input element 2 or
voltage (U3)/current (I3) of input element 3.
Reciprocal method
Data Update Interval
0.1 s
0.25 s
0.5 s
1 s
2 s
5 s
Only for the direct current input of the WT310HC, the maximum measurement range is 20 kHz.
Auto switching among six types: 1 Hz, 10 Hz, 100 Hz, 1 kHz, 10 kHz, and 100 kHz
Select OFF or ON (cutoff frequency at 500 Hz).
Requirements
• When the input signal level is 30% or more of the measurement range if the crest factor is set
to 3 (60% or more if the crest factor is set to 6)
• Frequency filter is ON when measuring voltage or current of 200 Hz or less.
Accuracy: ±(0.06% of reading)
Specifications
Single-Phase, Three-
Wire (1P3W)
(U1+U3)/2
(I1+I3)/2
P1+P3
S1+S3
Q1+Q3
P
2
i
PΣ
S Σ
P PΣ
− 1
i 1 −
( ) ( )
cos
S
S Σ
i
Measurement Range
25 Hz ≤ f ≤ 100 kHz
10 Hz ≤ f ≤ 100 kHz
5 Hz ≤ f ≤ 100 kHz
2.5 Hz ≤ f ≤ 100 kHz
1.5 Hz ≤ f ≤ 50 kHz
0.5 Hz ≤ f ≤ 20 kHz
Three-Phase, Three-
Wire (3P3W)
3
( S + 1 S 3 )
2
Three-Phase, Three- Three-Phase, Four-
Wire (3V3A) Wire (3P4W)
(U1+U2+U3)/3
(I1+I2+I3)/3
P1+P2+P3
S1+S2+S3
3
( S 1 + S 2 + S 3 )
3
Q1+Q2+Q3
IM WT310-02EN