YOKOGAWA WT1800 User Manual page 93

Add the following values to the current and power accuracies of 5 A input elements.
AC input signal: 0.006 × I
DC input signal: 0.006 × I
I is the current reading (A). Even if the current input decreases, the influence from self-generated heat continues until the shunt
resistor temperature decreases.
• Accuracy changes caused by data update interval
When the data update interval is 50 ms, add 0.1% of the reading. When the interval is 100 ms, add 0.05% of the reading.
• Guaranteed accuracy ranges for frequency, voltage, and current
All accuracy figures for 0.1 Hz to 10 Hz are reference values.
The voltage and power accuracy figures for 30 kHz to 100 kHz when the voltage exceeds 750 V are reference values.
The current and power accuracy figures for DC, 10 Hz to 45 Hz, and 400 Hz to 100 kHz when the current exceeds 20 A are
reference values.
• The accuracy when the crest factor is 6 is the same as that when the crest factor is 3 after doubling the measurement range.
Item
Power factor (λ) influence
Line filter influence
Lead and lag detection
(Phase angle Φ's
D (lead) and G (lag))
Symbol s in the reactive
power QΣ computation
Temperature coefficient
Effective input range
Maximum display
Minimum display
Lower limit of measurement
frequency
Accuracy of apparent power S Voltage accuracy + current accuracy
Accuracy of reactive power Q
Accuracy of power factor λ
Accuracy of phase angle Φ
Accuracy at 1 year
IM WT1801-03EN
2
% of reading
2
% of reading + 0.004 × I% of reading
Specifications
When λ = 0
Apparent power reading × 0.1% in the range of 45 Hz to 66 Hz.
For other frequency ranges, see below. Be aware that these figures are reference values.
5 A input element and external sensor input: apparent power reading × (0.1 + 0.05 × f [kHz])%
50 A input element and direct input: apparent power reading × (0.1 + 0.3 × f [kHz])%
When 0 < λ < 1
(Power reading) × [(power reading error %) + (power range error %) × (power range/indicated
apparent power value) + {tan Φ × (influence when λ = 0)%}],
where Φ is the phase angle between the voltage and current.
When the cutoff frequency (fc) is 100 Hz to 100 kHz
Voltage and current
Up to approx. (fc/2) Hz: Add 2 × [1 − √{1/(1 + (f/fc)
Applies to frequencies less than or equal to 30 kHz
Power
Up to approx. (fc/2) Hz: Add 4 × [1 − √{1/(1 + (f/fc)
Applies to frequencies less than or equal to 30 kHz
When the cutoff frequency (fc) is 300 kHz to 1 MHz
Voltage and current
Up to approx. (fc/10) Hz: Add (20 × f/fc)% of reading.
Power
Up to approx. (fc/10) Hz: Add (40 × f/fc)% of reading.
The lead and lag of the voltage and current inputs can be detected correctly for the following:
• Sine waves
• When the measured value is 50% or more (100% or more when the crest factor is 6) of the
measurement range
• Frequency: 20 Hz to 10 kHz
• Phase difference: ±(5° to 175°)
s is the sign for the lead and lag of each element. It is negative when the voltage leads the
current.
Add ±0.03% of reading/°C within the range of 5°C to 18°C or 28°C to 40°C.
Udc, Idc: 0% to ±110% of the measurement range
Urms, Irms: 1% to ±110% of the measurement range
Umn, Imn: 10% to 110% of the measurement range
Urmn, Irmn: 10% to 110% of the measurement range
Power:
DC measurement: 0% to ±110%
AC measurement: 1% to 110% of the voltage and current ranges; up to ±110% of the power
range
However, the synchronization source level must meet the frequency measurement input signal
level. When the crest factor is set to 6, the lower limits are multiplied by 2.
140% of the rated voltage or current range
Depending on the measurement range, the following are the minimum values that are displayed:
• Urms, Uac, Irms, and Iac: 0.3% (0.6% when the crest factor is set to 6)
• Umn, Urmn, Imn, and Irmn: 2% (4% when the crest factor is set to 6)
Any values less than these lower limits are displayed as zero. The integrated current q is
dependent on the current value.
Data update rate 50 ms 100 ms 200 ms 500 ms 1 s
Lower limit of 45 Hz 25 Hz
measurement frequency
Accuracy of apparent power + (√(1.0004 − λ
±[(λ − λ/1.0002) + |cosΦ − cos{Φ + sin − 1((influence from the power factor when λ = 0)%/100)}|]
± 1 digit. The voltage and current must be within their rated ranges.
±[|Φ − {cos − 1(λ/1.0002)}| + sin − 1{(influence from the power factor when λ = 0)%/100}] deg ± 1
digit. The voltage and current must be within their rated ranges.
1.5 times the reading errors for the accuracy at 6 months
4 )}] × 100 + (20 × f/300k)% of reading
4
)}] × 100 + (40 × f/300k)% of reading
2 s
12.5 Hz 5 Hz 2.5 Hz 1.25 Hz 0.5 Hz 0.2 Hz 0.1 Hz
2 2
) − √(1 − λ )) × 100% of range
6.4 Accuracy
1
2
3
4
5
6
App
Index
5 s 10 s 20 s
6-9