YOKOGAWA CW140, User Manual, Page: 87 / 292

8-15
IM CW140-E
Instant Measure Mode
8
8.6 Computational Expressions
The computational expressions used for the Instant Measure mode are as
follows.
●
Rms-value Voltage
Vrms =
√
=
√
T
T
1
∫
0
v(t) 2 dt
T
T
1
t=0
v(t) 2 ∑
●
Rms-value Current
Arms =
√
=
√
T
T
1
∫
0
i(t) 2 dt
T
T
1
t=0
i(t) 2 ∑
●
Active Power
P =
T
T
1
∫
0
v ( t ) × i ( t ) dt
T
T
1
t=0
v (t) × i (t)
=
∑
●
Reactive Power
With reactive power meter method.
Q =
T
T
-1
∫
0
v (t) × i
(
t +
)
dt
)
T
T
-1
4
T
4
T
t=0
v (t)
×
i
(
t +
=
∑
v(t), i(t)
: Input signal
T : One period input signal
Polarity
Lag : +
Lead: –
●
Three-phase Unbalance Factor
Va
Vb
×
100
% Unbalance foctor =
• For 3
φ
3W
Vs = (V
12
+V
23
+V
31
)
2
1
: line-to-line voltages for the 3 φ 3W.
• For 3 φ 4W
In the equations,
V
12
, V
23
, V
31
for the 3 φ 3W are substituted with
V
1n
, V
2n
, V
3n
,
respectively.