ENGLISH 4/8
MI003074-E
OPERATING LOGIC
The module measures the following electrical quantities: Vrms, Irms, Watt, VAR,
VA, Frequency, Cos
and Active Energy, and provides the values in the
corresponding MODBUS registers.
In three-phase environments, measurements given above corresponding to any
phase are available, other than the three-phase value (except the frequency).
These measurements are rendered in both floating point and normalized format
(except Frequency and Active energy) between 0..+10000 (-10000 ..+10000 for
VAR e Cos
). Active energy value is stored in memory and when the instrument is
switched off, the last value before switching is kept in memory.
The module output can transmit one of the following quantities: Vrms, Irms, Watt,
cos
as either a current or voltage value. If the instrument is set for three-phase
measurements, it transmits automatically the three-phase value of the selected
measurement. However, via MODBUS register, the user can choose to transmit
the measurement corresponding to any phase: A, B, C.
The user can set through MODBUS the values
MIN
and
MAX
of the
measurement to transmit corresponding to 0% and 100% of the analog output.
For example, if the signal is transmitted as current 4..20 mA and the quantity to
transmit is voltage Vrms in the 10..300 V range, (therefore
MIN=10, MAX=300
),
then if Vrms measured is 10V, analog output will be 4mA, while if Vrms=300V
output will be 20mA. In the intermediate points the behaviour is linear. The analog
output values saturate at approximately 11 V for voltage output and at 22mA for
current output (analog output clamped at 110 %).
If network frequency oscillates more than 30 mHz from rated values (50 o 60 Hz),
it’s possibile to compensate errors on measurements of Power and Energy
caused by these variations. This option is selectable via MODBUS register. Vrms
and Irms measurements are not influenced by these variations.
When the module is switched on, the appropriate setting coefficients are
measured (depending on the choice of 50 or 60 Hz frequency). All the settings
made will be automatically loaded when the module is reset.
NOTE: without load connected to the S203RC-D, only the (displayed) voltage
and frequency assume a corrected value.
ROGOWSKI’S COIL
Rogowski’s coil have been designed for accurate non-intrusive measurement of
AC, pulsed DC or complex waveforms. To use in an appropriate way,
- wrap the ring on the conductor so that the arrow symbol (stamped in the ring) is
oriented in the same direction of the current in the conductor
- make sure that the connections are performed properly: the white output wire is
positive (+), the brown wire is the negative (-).
