M2x2/EN M/F User Manual
Page 20
iSTAT M2x2
8.3.1 Voltage
All versio
ns of the M2x2 except for the 3-phase 3-wire versions, measure the true RMS
value of the phase voltages (U
a
, U
b
, U
c
) connected to the unit. The three line-to-line voltages
(U
ab
, U
bc
, U
ca
), then the average phase voltage (U) and average line voltage (U
) are
calculated from these measured parameters. For 3-phase 3-wire balanced systems, the
M2x2 creates a virtual neutral internally.
The 3-phase 3-wire versions of the M2x2 measure the true RMS value of the phase to phase
voltage.
All voltage measurements are available via communication and on the LCD display.
8.3.2 Current
The M2x2 measures the true RMS value of the phase currents (Ia, Ib, Ic) connected to the
unit. The neutral current (In), then the average of all phase currents and the sum of all phase
currents (It) are calculated from the three phase currents.
All current measurements are available via communication and on the LCD display.
8.3.3 Frequency
The system frequency is calculated from the time period of the measured voltage and can be
viewed from both the M2x2 display and the remote communications link.
8.3.4 Harmonics (THD)
The percentage total harmonic distortion (%THD) value is the ratio of the sum of the powers
of the harmonic frequencies (to 32
nd
) above the fundamental frequency to the power of the
fundamental frequency. This sum of the powers is a geometric total, formed by taking the
square root of the sum of the squares of the amplitude of each of the harmonics.
The M2x2 provides %THD values for each phase current, each phase voltage, and for the
line voltages.
8.3.5 Power
The M2X2 provides accurate measurement of active (P
a
, P
b
, P
c
, P
t
), reactive (Q
a
, Q
b
, Q
c
,
Q
t
) and apparent power (S
a
, S
b
, S
c
, S
t
). For a four-wire system the powers are calculated
both for each phase separately and as a total. For a three-wire system only total power
values are measured.
All the available power parameters can be viewed using either the LCD display or via the
remote communications link.
8.3.6 Power factor
The power factor is calculated as a quotient of active and apparent power for each phase
separately (cosa, cosb, cosc) and as a total (cost). A positive sign and a coil symbol
denotes an inductive load (a consumer) whilst a negative sign and a capacitor symbol
defines a capacitive load (a generator). For correct display of PF via application of the
alarm, ePF (extended power factor) is applied. It illustrates power factor with one value as
described in the table below. For a display on LCD both of them have equal display function:
between −1 and −1 with the icon for inductive or capacitive load.
Load C
L
Angle
[°]
−180 −90 0 +90
+180
(179.99)
PF −1 0 1 0 −1
All available power factor parameters can be read from the LCD display or via the remote
communications link.
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