Circutor Computer SMART III 12, Instruction Manual

Page: 83 / 114

For other voltages or conditions not included in the table, the value of C/K can be obtained by means
of a simple calculation.

Calculating the C/K Factor
The equation for calculating the C/K factor is:
V K
Q
K
I
K C C
⋅ ⋅
= =
3
/
where
, Ic
: is the smallest capacitor current.
K
: the current transformer transformation ratio.
To calculate
Ic
it is necessary to know the reactive power of the smallest capacitor Q and the network
voltage V .
V .
Q
C
I
3
=
The transformation ratio K is calculated as:
sec
I
prim
I K
/
=
where, Iprim : is the nominal current of the transformer primary.
Isec : is the current of the transformer secondary.
Example: In a 400 V device the smallest capacitor is of 60 kvar with a current transformer having a
ratio of 500/5, and the calculation would be made as follows:
Current of the smallest capacitor,
Ic:
A I
C
6 , 86
400 3
60000
=
⋅
=
K Factor
100 5 / 500
= =
K
The C/K value is:
0.866
.
If the power of 60 kvar is referenced at 440 V, it should be multiplied by Vred
2
/440
2,
in which case the C/K value of the previous example would be 0.72 .
If the C/K is configured lower than the actual value, connections and disconnections
would occur continuously with few load variations (the system performs more opera-
tions than necessary).
If the C/K is configured higher, the regulator requires a higher demand for reactive
power in order to switch and perform fewer operations.
Press the key to enter edit mode. It is identified by the symbol and the flashing of the
digits to be modified.
83
Instruction Manual
Computer SMART III