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16.3 Functions
Item
Measurement range
Frequency filter
Accuracy
Computation
Item
Computing equation of apparent power (VA), reactive power (var), power factor (PF), and phase angle (deg)
Active Power (W)
Wiring System
Single-phase,
W
two-wire
W
i
Single-phase,
three-wire
ΣW=W
(i=1, 3)
W
i
Three-phase,
three-wire
ΣW=W
(i=1, 3)
W
i
Three-phase,
four-wire
ΣW=W
(i=1, 2, 3)
W
i
Three-voltage,
(W
2 has no physical
three-current
meaning)
(i=1, 2, 3)
ΣW=W
16-6
Specifications
Auto switching among six types: 1 Hz, 10 Hz, 100 Hz, 1 kHz, 10 kHz, and 100 kHz.
Select OFF or ON (cutoff frequency of 500 Hz).
Requirements
•
The amplitude of the measure signal is at least 30% (greater than or equal to 60% if the crest
factor is set to 6) of the rated value of the voltage or current range.
•
Frequency filter is ON when measuring voltage or current of 200 Hz or less.
Accuracy
±(0.06% of reading)
Specifications
Apparent Power (VA)
VA=V•A
VA
=V
A
i
i•
i
ΣVA=VA
W
VA
1+
3
1+
VA
=V
A
i
i•
i
3
ΣVA=
W
(VA
1+
3
2
VA
=V
A
i
i•
i
ΣVA=VA
W
W
VA
1+
2+
3
1+
VA
=V
A
i
i•
i
3
ΣVA=
W
(VA
1+
3
3
+VA
)
3
Note
•
The WT210/WT230 computes apparent power (VA), reactive power (var), power factor (PF),
and phase angle (deg) from voltage, current, and active power through digital computation. If
distorted signal is input, the value obtained on this instrument may differ from that obtained on
other instruments using a different measurement principle.
•
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 VA or var, and error is displayed for PF and deg.
•
The accuracy of detecting lead or lag is defined for a voltage and current input that is at least
50% (range rating if the crest factor is set to 6) of the rated range.
Detection accuracy: ±5 deg (20 Hz to 2 kHz)
For ±Σvar computation, when the current leads the voltage, each var value is computed as a
•
negative value; when the current lags the voltage, the value is computed as a positive value.
Reactive Power (var)
var=
2–
2
(VA)
W
3
var
=
2–
2
(VA
)
W
i
i
i
Σvar=var
var
1+
3
VA
)
1+
3
var
= (VA
2–
2
i
)
W
i
i
Σvar=var
VA
var
2+
3
1+
2+
2–
2
var
= (VA
i
)
W
i
i
Σvar=var
VA
var
1+
2
1+
3
i: Input element number
Power Factor (PF) Phase Angle (deg)
W
PF=
VA
W
i
PF
=
i
VA
i
ΣW
ΣPF=
ΣVA
var
3
W
1
deg=
cos–
(
)
VA
W
i
–1
deg
=
cos
(
)
i
VA
i
ΣW
Σdeg=
–1
cos
(
)
ΣVA
IM 760401-01E
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