YOKOGAWA CW140, Руководство пользователя, Страница: 88 / 292

IM CW140-E
8-16
8.6 Computational Expressions
Computational Expressions of Instant Measure Mode
The CW140 performs the computations summarized below by using the
measured values of V, A, W and Q variables.
With reactive power
meter:
cos
-1
(
( ∑ P )
2
+( ∑ Q)
2
)
Without reactive power
meter:
cos
-1
(
∑
P /
∑
VA)
1 φ 2W
1 φ 3W
3 φ 3W
With reactive power
meter:
Without reactive power
meter:
P / VA
Q i=
(VAi)
2
– Pi
2
i=1, 2
∑
Q=Q1+Q2
Q i=
(VAi)
2
– Pi
2
i=1, 3
∑
Q=Q1+Q3
Q i=
(VAi)
2
– Pi
2
i=1, 3
∑
Q=Q1+Q3
Q i=
(VAi)
2
– Pi
2
i=1, 2, 3
∑
Q= Q1+Q2+Q3
The rating depends on the
ranges of variables V and A. The rating depends on the
ranges of variables V and A.
Same as that of active power.
Same as that of active power.
± 1.000 ± 180.0
VAi=Vi ×
Ai
i=1, 3
∑ VA=
3 / 2 (VA1+VA3)
VAi=Vi × Ai
i=1, 2, 3
∑
VA=
VA1+VA2+VA3
VAi=Vi × Ai
i=1, 2
∑
VA=VA1+VA2
If the reactive power
method is used:
If the reactive power
method is not used:
cos
-1
(P / VA)
Q= (VA)
2
– P
2
VAi=Vi ×
Ai
i=1, 3
∑
VA=
3 / 2 (VA1+VA3)
VA = V × A
With reactive power
meter:
( ∑ P)
2
+( ∑ Q)
2
Without reactive power
meter:
∑
P /
∑
VA
3 φ 3W3i
3 φ 4W
Limits of computation
–1 to +1
–180 to +180
Read-out resolution
∑ P
∑ P
Reactive Power 2
(Without reactive
power meter method.)
Apparent Power Power Factor Phase Angle
P / P
2 +
Q
2
cos
-1
(P / P
2 +
Q
2
)
TIP
• In the case of distorted-wave input, the result of computation may differ from that of any other instru-
ment that uses a different measuring principle.
Lag Lead
180 180 Phase difference
Polarities of Active Power, Reactive Power, Power Factor and Phase Angle
Active power
Reactive power
Power factor
Phase angle –
+
–
– +
+
+
+ +
–
–
– –
–
+
+
90 90 0
• The phase lag or lead means that of current in reference to voltage.
• Even if the reactive power method is not used, the polarities of reactive power 2, power factor and
phase angle are determined by those of reactive power 1.