User’s Manual WM3M4 &WM3M4C
5.3 Calculation and display of measurements
This chapter deals with capture, calculation and display of all supported measurement quantities.
5.3.1 Voltage
Voltage related measurements are listed below:
Real effective (RMS) value of all phase voltages (U
1
, U
2
, U
3
) and phase-to-phase voltages (U
12
, U
23
,
U
31
).
Phase and phase-to-phase voltage angles (
12
,
23
,
31
)
Figure 32: Voltage equations
All voltage measurements are available through communication.
5.3.2 Current
WM3M4 & WM3M4C energy meter measures:
real effective (RMS) value of phase currents
Figure 33: Current equation
All current measurements are available on communication.
5.3.3 Active, reactive and apparent power
Active power is calculated from instantaneous phase voltages and currents. All measurements are
seen on communication.
5.3.4 Power factor (PF) and power angle
PF or distortion power factor is calculated as the quotient of active and apparent power for each
phase separately and total power angle. It is called distortion power factor since true (distorted)
signals are using in equation. A symbol for a coil (positive sign) represents inductive load and a symbol
for a capacitor (negative sign) represents capacitive load.
5.3.5 Frequency
Network frequency is calculated from time periods of measured voltage. Instrument uses
synchronization method, which is highly immune to harmonic disturbances.
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