32
6.5.3 Calculation of c/k
Formula 1 Calculation of c/k
where
I
A
= Response current in mA to be set
Q
smallest stage
= Capacitor power rating of the smallest stage in var
(not the total system power rating)
V
= Network voltage in volts at the primary side of the current transformer
k
= Transformer ratio (primary side / secondary side)
Table 2 c/k settings at 400 V AC and 50 Hz
c/k settings for 400 V AC 50 Hz networks
Current
Stage rating
(not total) in kvar of the power factor correction system
A /A
k
2.5
5 6.25
7.5
10 12.5
15
20
25
30
40
50
60 100
30 / 5
6
400 800 980 1200 1600
40 / 5
8
300 600 740 900 1200 1500
50 / 5
10
240 480 590 720 960 1200 1440
60 / 5
12
200 400 490 600 800 1000 1200 1600
75 / 5
15
160 320 390 480 640 800 960 1280 1600 1920
100 / 5
20
120 240 300 360 480 600 720 960 1200 1440 1920
150 / 5
30
80 160 200 240 320 400 480 640 800 960 1280 1600 1920
200 / 5
40
60 120 150 180 240 300 360 480 600 720 960 1200 1440
250 / 5
50
50 100 120 140 190 240 290 380 480 580 770 960 1150 1920
300 / 5
60
40
80 100 120 160 200 240 320 400 480 640 800 960 1600
400 / 5
80
30
60
80
90 120 150 180 240 300 360 480 600 720 1200
500 / 5
100
20
50
60
70 100 120 140 190 240 290 380 480 580 960
600 / 5
120
40
50
60
80 100 120 160 200 240 320 400 480 800
750 / 5
150
30
40
50
60
80 100 130 160 190 260 320 380 640
1000 / 5
200
20
30
40
50
60
70 100 120 140 190 240 290 480
1500 / 5
300
20
20
30
40
50
60
80 100 130 160 190 320
2000 / 5
400
20
30
40
50
60
70 100 120 140 240
2500 / 5
500
20
30
40
50
60
80 100 120 190
3000 / 5
600
20
30
40
50
60
80 100 160
4000 / 5
800
20
30
40
50
60
70 120
5000 / 5
1000
20
30
40
50
60 100
6000 / 5
1200
20
30
40
50
80
7000 / 5
1400
20
30
40
70
If the ratings of the stages and the current transformers are not to be found in the table, or the
nominal voltage of the power factor correction system is different, the above formula must be
used to calculate the c/k setting.
I
A
= 0.65 · Q
smallest stage
· 1000 ≈ 0.375 ·
Q
smallest stage
· 1000 [mA]
V · √3 · k
V · k
