CIRCUTOR computer SMART Series (Available until stock) User 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