Hioki PW3360-21 - Page 237

A3
Appendix
Additionally, since the sum of the voltage and current vectors always equals 0 under
these conditions, the instrument internally calculates the third voltage ( ) and cur-
rent ( ) values as follows:
= -
= - -
Since the values calculated internally are a
lso applied to the 3-phase total
reactive power Q, apparent power S, and power
factor PF values, these values can
also be calculated accurately in the event of an unbalanced state (PF/Q/S calcula-
tion selection: when using RMS calculation).
See: "PF/Q/S calculation" (p.66)
However, because the three phases are calculated from two power values in 2-watt-
meter measurement, it is not possible to
check the
power balance for individual
phases. If you wish to check the power balance for individual phases, use 3-wattme-
ter (3P3W3M) measurement.
U
3
I
2
U
3
U
1
U
2
I
2
I
1
I
3
U
3
, I
2
Item 3P3W2M
Relative
merits
3P3W3M
Voltage
U1 =
= -
U2
= -
U3
= -
= -
Current
I1 =
I2
I3
= - -
Active
power
P1
Since the three phases
are calculated from two
power meter, it is not
possible to check the
active power balance for
individual phases.
<
It is possible to check the
active power balance for
individual phases.
P2
P3 -
P
+
= + +
See equation (2).
=
+ +
Apparent
power
(When the
PF
/Q/S
calcula-
tion selec-
tion is set
to RMS)
S1 U
1
I
1
Since calculations are
based on the line-to-line
voltage and phase (line)
current, apparent power
values are not generated
for individual phases.
< u
1
I
1
Since calculations are
based on the phase volt-
age and phase (line) cur-
rent, it is possible to
check th
e apparent
power for individual
phases.
S2 U
2
I
3
u
2
I
2
S3
U
3
I
2
u
3
I
3
S
(U
1
I
1
+U
2
I
3
+U
3
I
2
)
=
(U
1
I
1
+U
2
I
2
+U
3
I
3
)
U
1
U
1
u
1
u
2
U
2
U
2
u
2
u
3
U
3
U
1
U
2
U
3
u
3
u
1
I
1
I
1
I
3
I
2
I
2
I
1
I
3
I
3
U
1
I
1
u
1
I
1
U
2
I
3
u
2
I
2
u
3
I
3
U
1
I
1
U
2
I
3
u
1
I
1
u
2
I
2
u
3
I
3
u
1
I
1
u
2
I
2
u
3
I
3
3
3
3
3
In 3P3W2M measurement, the instrument inputs the 3-phase line’s T-
phase current as each current’s I2 parameter. For display purposes,
the 3-phase line’s T-phase current value is shown as the I2 current, and
the 3-phase line’s S-phase calculated value is shown as the I3 current.