YOKOGAWA WT1800 User Manual page 117

Measurement
Function
ΣI[A]
Three-phase,
three-wire with
three-voltage,
three-current
method.
3P3W(3V3A)
ΣP[W]
Three-phase, four-wire
3P4W
ΣP[W]
Three-phase, three-wire
with three-voltage,
three-current method.
3P3W(3V3A)
Torque
Speed
Pm
AUX1
AUX2
*1 It is necessary to set the cutoff frequency of the HS filter to match the frequency of the circuit
under measurement.
*2 This value does not have physical meaning when three-phase AC wiring is used.
Note
• In the above equations, u(n) and i(n) denote the nth instantaneous voltage value and the nth
instantaneous current value, respectively.
• n indicates the nth item within the data capturing interval. N indicates the number of sampled data items
within the data capturing interval. HSFilter indicates that the items enclosed in the brackets that follow
have passed through an HS Filter low-pass filter.
• The HS filter is a second order Butterworth filter.
• When the HS filter is enabled, the characteristics of the second order Butterworth filter result in the
attenuation (averaging) of the amplitude of the AC components. The response also becomes slower.
• The 16-bit data (instantaneous voltage and current values) from the A/D converter is converted to single-
precision floating point data before it undergoes computation.
IM WT1801-03EN
Appendix 1 Symbols and Determination of Measurement Functions
Methods of Computation and Determination
rms
True rms value
mean
*1
Rectified mean value calibrated to the rms value
π N−1
1
× HSFilter [{|i1(n)|+|i2(n)|+|i3(n)|}/3]
N
2 2
n=0
rmean *1
Rectified mean value
dc *1
1
Simple average
N
N−1
1
Active power
N
n=0
N−1
1
Active power
N
n=0
1
Simple average
N
1
Simple average
N
See page App-8, "Monitor output Pm".
1
Simple average
N
1
Simple average
N
1 N−1
HSFilter [{i1(n) +i2(n)
2
N
n=0
N−1
1
HSFilter [{|i1(n)|+|i2(n)|+|i3(n)|}/3]
N
n=0
N−1
HSFilter [{i1(n)+i2(n)+i3(n)}/3]
n=0
HSFilter [u1(n)×i1(n)+u2(n)×i2(n)+u3(n)×i3(n)]
HSFilter [u1(n)×i1(n)+u2(n)×i2(n)]
N−1
HSFilter [torque(n)]
n=0
N−1
HSFilter [speed(n)]
n=0
N−1
HSFilter [aux1(n)]
n=0
N−1
HSFilter [aux2(n)]
n=0
+i3(n) }/3]
2 2
Index
App-11
1
2
3
4
5
6
App