YOKOGAWA wt3000, Руководство пользователя, Страница: 37 / 384

2-11
IM 760301-01E
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App
Index
Faunctional Description
Scaling «For procedures, see sections 4.4 and 4.5.»
When applying current signals via an external current sensor or applying voltage or
current signals via the external VT (voltage transformer) or CT (current transformer), the
transformation ratio or coefficient can be specified.
• When Applying Current Signals via an External Current Sensor
The output of current sensors that output voltage, such as shunts and clamps, can be
input to the current sensor connector (EXT) and measured. Set how many millivolts
the current sensor outputs when 1 A of current flows (transformation ratio). Then, the
input signal can be made to correspond to the numeric data or waveform display data
that are obtained when the current is directly applied to the input terminals.
Measurement Function Transformation Data before Transformation
Ratio Transformation Result
Current I E I
S
(current sensor output) I
S
/E
Active power P E P
S
P
S
/E
Apparent power S E S
S
S
S
/E
Reactive power Q E Q
S
Q
S
/E
Max./Min. current value Ipk E Ipk
S
(current sensor output) Ipk
S
/E
• When Applying Voltage or Current Signals via an External VT or CT
• VT ratio and CT ratio
The input signal can be converted into numeric data or waveform display data of the
voltage or current before transformation by setting the VT ratio, CT ratio, and power
coefficient (coefficient multiplied to the power determined from the voltage and current).
• Power factor
You can multiply a coefficient to the measured active power, apparent power, and
reactive power to be displayed by setting a power factor (SF).
Measurement Function Data before Transformation Transformation Result
Voltage U U
2
(secondary output voltage of the VT) U
2
× V V: VT ratio
Current I I
2
(secondary output of the CT) I
2
× C C: CT ratio
Active power P P
2
P
2
× V × C × SF SF: Power coefficient
Apparent power S S
2
S
2
× V × C × SF
Reactive power Q Q
2
Q
2
× V × C × SF
Max./Min. voltage value Upk Upk
2
(secondary output of the VT) Upk
2
× V
Max./Min. current value Ipk Ipk
2
(secondary output of the CT) Ipk
2
× C
Crest Factor «For procedures, see section 4.6.»
The crest factor is defined as the ratio of the peak value of the waveform to the rms value.
Peak value
Rms value
Crest factor (CF) =
Peak value
Rms value
Input signal
waveform
The crest factor on the WT3000 is determined by the maximum peak value that can be
applied for rated input in terms of a multiplication factor.
Peak value that can be input
Measurement range
Crest factor (CF) =
2.3 Measurement Conditions