YOKOGAWA wt3000 - Page 367

App-35
IM 760301-01E
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App
App
Index
Appendix
Efficiency Compensation
In the efficiency equation η = A/B, the compensation value Err# in the table below is
subtracted from denominator B according to the element or wiring unit included in
numerator A.
Err# = U#×U#/RU×sf# + I#×I#×RI×sf#
Err# = ΣErr# (total of Err# of all elements included in Σ)
Element or Wiring Unit
Element#
ΣA,B
Compensation Err#
U#: Measured voltage (rms, mean, r-mean, or dc) depending on the voltage
mode. # is the element number.
I#: Measured current (rms, mean, r-mean, or dc) depending on the current
mode. # is the element number.
R
U
: Input resistance (10 MΩ) of the voltage input terminal
R
I
: Input resistance (5.5 mΩ) of the current input terminal
sf#: Scaling factor for power. # is the element number.
Example
where ΣA: Element 1 and 2, ΣB: Element 3 and 4
η =
PΣA
PΣB
The efficiency compensation for above
η =
PΣA
{PΣB – ((U1 × U1/R
U
× sf1 + I1×I1 × R
I
× sf1) +
(U2 × U2/R
U
× sf2 + I2 × I2 × R
I
× sf2))}
Compensation for the Two-Wattmeter Method
The computation below is performed on the element or wiring unit wired to 3P3W
(3V3A).
Example: When elements 1, 2, and 3 are set to 3P3W (3V3A)
Computation step 1: Calculation of compensation values
• Power: Compensation SP’ = {The average of ((–(u(n)1 + u(n)2)/3)×
(i(n)1 + i(n)2 + i(n)3))}
• Watt hour (total): Compensation SWP’ = {WP of ((–(u(n)1 + u(n)2)/3)×(i(n)1 +
i(n)2 + i(n)3))}
• Watt hour (+): Compensation SWP(+)’ = {WP(+) of ((–(u(n)1 + u(n)2)/3)×
(i(n)1+ i(n) 2 + i(n)3))}
• Watt hour (–): Compensation SWP(–)’ = {WP(–) of ((–(u(n)1 + u(n)2)/3)×
(i(n)1+ i(n) 2 + i(n)3))}
u(n) and i(n) are instantaneous voltage and current (sampled data of voltage and
current signals), respectively.
Computation step 2: Add the compensation value to the measured value
•SP” = SP + SP’×sf#
•SWP” = SWP + SWP’×sf#
•SWP(+)” = SWP(+) + SWP(+)’×sf#
•SWP(–)” = SWP(–) + SWP(–)’×sf#
sf#: Scaling factor of the first element in the wiring unit (element 1 in this example)
Note
This function can be set only when the wiring system is set to 3P3W (3V3A) on models with
the delta computation option.
Appendix 8 Compensation Function