CIRCUTOR computer SMART Series (Available until stock) - Manual (Page 24)

M98235701-03-12A Computer Smart 6/Computer Smart 12
- 23 -
When the 440 V capacitor power reference is used for a 400 V grid voltage, the following table is used:
CT Ratio
(I
p
/I
s
)
Power in kvar of the smallest stage, in kvar, at 440 V
2.5 5.00 7.5 10.0 12.5 15.0 20.0 25.0 30.0 40.0 50.0 60.0 75.0 80.0
150/5 0.09 0.18 0.27 0.36 0.45 0.54 0.72 0.90
200/5 0.07 0.14 0.20 0.27 0.34 0.41 0.54 0.68 0.81
250/5 0.05 0.11 0.16 0.22 0.27 0.33 0.43 0.54 0.65 0.87
300/5 0.05 0.09 0.14 0.18 0.23 0.27 0.36 0.45 0.54 0.72 0.90
400/5 0.07 0.10 0.14 0.17 0.20 0.27 0.34 0.41 0.54 0.68 0.81
500/5 0.05 0.08 0.11 0.14 0.16 0.22 0.27 0.33 0.43 0.54 0.65 0.81 0.87
600/5 0.05 0.07 0.09 0.11 0.14 0.18 0.23 0.27 0.36 0.45 0.54 0.68 0.72
800/5 0.05 0.07 0.08 0.10 0.14 0.17 0.20 0.27 0.34 0.41 0.51 0.54
1000/5 0.04 0.05 0.07 0.08 0.11 0.14 0.16 0.22 0.27 0.33 0.41 0.43
1500/5 0.04 0.05 0.05 0.07 0.09 0.11 0.14 0.18 0.22 0.27 0.29
2000/5 0.04 0.05 0.07 0.08 0.11 0.14 0.16 0.20 0.22
2500/5 0.04 0.05 0.07 0.09 0.11 0.13 0.16 0.17
3000/5 0.04 0.05 0.05 0.07 0.09 0.11 0.14 0.14
4000/5 0.04 0.05 0.07 0.08 0.10 0.11
IMPORTANT!:
When the C/K adjustment is configured under the real values, there will be a series of continuous
connections and disconnections with minor load variations. (The system performs more operations than
those actually needed).
When the C/K adjustment is configured as "high" (10%), the regulator will need a higher reactive power
demand to perform the switching operations and, therefore, perform fewer operations.
Calculation of the C/K Factor
In the case of values that have not been included in the table, the C/K factor can be calculated as follows:
The reactive power of the smallest capacitor Q and the grid voltage U must be known. The current of this
capacitor will be then calculated as V .
Q
C
I
3
=
The transformation ratio of the current transformer must also be known. This is the K factor:
sec
I
prim
I K /
=
where: Iprim is the nominal current of the transformer's primary (for example, it would be 250A in a 250/5)
Isec is the transformer's secondary current. Usually 5 A.
Therefore, the C/K factor will be: V K
Q
K
I
K C C
⋅ ⋅
= =
3
/
For example: In a 400V unit, the smallest capacitor is 60 kVAr with a current transformer with a 500/5 ratio.
The calculation is as follows:
K factor
100 5 / 500
= =
K
Current of the smallest capacitor
A I
C
6 , 86
400 3
1000 60
=
⋅
⋅
=
C/K value
866 , 0
100
6 , 86
/
= = =
K
Ic
K C
When the 60kvar power is referenced to 440 V, it must be multiplied by Ugrid^2/440^2, so that the previous
example would be:
A I
C
6 . 71
2 ^ 440 3
400 * 1000 60
=
⋅
⋅
= 72 , 0 /
=
K C