Carlo Gavazzi WM5-96 - Manual (Page 36)

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WM5-96 Instruction Manual
Programming WM5 96
Example 1
How to stabilize the value of the VL-N variable displayed on the
display, fluctuating from 222V and 228V.
The parameters of the digital filter have to be programmed as follows:
RANGE: the variable has fluctuations within the mean value whose
amplitude is equal to ±0,75% of the full scale rated value of the vari-
able itself (obtained by the following calculation: (228-222)/ 2= ±3V,
then ±3*100/400V= ±0,75% where 400V is the phase-neutral rated
value of an AV5 input). The “range” parameter, representing the action
range of the digital filter, is to be programmed to a value which must
be slightly higher than the percentage amplitude of the fluctuation: ex.
1.0%.
COEFFICIENT: if the new value measured by the instrument is within
the action range of the filter, the new displayed value is obtained by
adding algebrically the previous value to the variation divided by the
filtering coefficient. As a consequence, a value higher than this coeffi-
cient implies a longer settling time and therefore a better stability. You
generally obtain the best result by setting the filtering coefficient to a
value equal to at least 10 times the range parameter value.
In the following example: 1,0*10=10, the stability of the filtering coef-
ficient can be improved by increasing the filtering coefficient, the
admitted values are included within 1 and 255.
Example 2
How to stabilize the value of the displayed System Active Power
(W
∑), fluctuating between 300kW and 320kW (the load is connect-
ed to the instrument by means of a 300/5A CT and a direct meas-
ure of the voltage).
The parameters of the digital filter must be programmed as follows:
RANGE: the variable has fluctuations within the mean value whose
amplitude is equal to ±2,78% of the full scale rated value of this vari-
able. This value is obtained by the following calculation: (320-300)/ 2=
±10kW, then ±10*100/360kW= ±2,78%, where 360kW is the rated
value of the System Active Power of an AV5 input, at the above men-
tioned CT and VT ratios and obtained by means of the following for-
mula: (320-300)/ 2= ±10kW, then ±10*100/360kW= ±2,78%, where
360kW is the rated value of the System Active Power of an AV5 input
at the above mentioned CT and VT ratios and obtained by means of
the following formula: “VLN * VT * IN * CT * 3” where VLN = rated input
voltage (400V for the AV5 input), VT= primary/secondary ratio of the
voltage transformer being used, IN = rated current (5A for the AV5 type
input), CT = primary/secondary ratio of the voltage transformer being
used (in this example “400*1*5*60*3=360kW).
The RANGE parameter, representing the digital filtering coefficient
action range, is to be programmed to a value which must be slightly
higher than the percentage of the fluctuation: ex. 3.0%.
COEFFICIENT: if the new value acquired by the instrument is within the filter-
ing action range, the new displayed value is obtained by adding algebrically
the previous value to the variation divided by the filtering coefficient. As a con-
sequence, a value higher than this coefficient implies an higher settling time
and therefore a better stability. Generally speaking the best result is obtained
setting the filtering coefficient to a value equal to at least 10 times the value of
the range parameters. In the example: 3.0*10=30. In order to improve the sta-
bility you can increase the filtering coefficient, the admitted values are includ-
ed within 1 and 255.
Digital filter programming
Examples