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3.3
Connection Modes
3.3.1
Four-wire Three-phase Current with Any Load
Depending on the measuring method some quantities to be measured are not available. For the
method according to DIN, for example the apparent power S or S
be calculated.
3.3.2
Single-phase AC
The measuring path for the voltage is A-N for the voltage and A for the other quantities. This
applies also for the power values. The apparent power according to DIN, the reactive power Q
DIN and the asymmetry are not valid.
3.3.3
Four-wire Three-phase Current with Symmetrical Load
Current A and voltage A-N are available. You can display the same measured quantities as for
Single-phase AC. For power Σ, the value calculated from U and I must be multiplied by 3. For
power, power factor, cos φ, phase angle and energy only the sum is relevant. The measurement
values Asymmetrical U or I are not available. THD and harmonics can be derived for A only.
3.3.4
Three-wire Three-phase Current with Symmetrical Load
For this connection mode, an artificial neutral point is formed via resistors. Since this internal
neutral point is connected to the grounding conductor, it cannot be used here. The reactive
power (Standard) can be derived from U
Equation 11:
64
3
∑
=
Q
64
ν
=
1
You have to calculate u
Q1, the adequate phasors are used. For the reactive power (Standard), sample points, which are
shifted by 90°, are used for the voltage.
Equation 12:
64
3
∑
=
P
64
ν
=
1
To calculate the active power of the fundamental P
surement values Asymmetrical U or I are not available. THD and harmonics cannot be calcu-
lated. The apparent power is the multiplication of the RMS values voltage and current, e.g.:
Power Meter SICAM P 7KG7750/55, Manual
E50417-B1076-C340-A6, Edition 09.2013
u
i
ν
ν
32
1
from u
- u
32
3E
2E
π
−
j
⋅
u
e
2
i
ν
ν
32
1
1
and I
:
32
1
. To calculate the reactive power for the fundamental
the adequate phasors are used. The mea-
1
3.3 Connection Modes
are available; only S
can
DIN
tot
49
3
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