63
Table 7.4 MCCB Selection for Circuits with PF-Correction
a) 230V, 50Hz Circuit
Capacitor rating
kVA
5
10
15
20
25
30
40
50
75
100
150
200
300
400
µ
F
301
602
903
1203
1504
1805
2407
3009
4513
6017
9026
12034
18052
24069
Single-phase circuit
Capacitor
rated
current
(A)
21.7
43.5
65.2
87.0
108.7
130.4
173.9
217.4
326.1
434.8
652.2
869.6
1304.3
1739.1
MCCB
rated
current
(A)
40
75
100
125
175
200
250
350
500
700
1000
1400
2000
2500
Three-phase circuit
Capacitor
rated
current
(A)
12.6
25.1
37.7
50.2
62.8
75.3
100.4
125.5
188.3
251.0
376.5
502.0
753.1
1004.1
MCCB
rated
current
(A)
20
40
60
75
100
125
150
200
300
400
600
800
1200
1500
b) 230V, 60Hz Circuit
Capacitor rating
kVA
5
10
15
20
25
30
40
50
75
100
150
200
300
400
µ
F
251
501
752
1003
1254
1504
2006
2507
3761
5014
7522
10029
15043
20057
Single-phase circuit
Capacitor
rated
current
(A)
21.7
43.5
65.2
87.0
108.7
130.4
173.9
217.4
326.1
434.8
652.2
869.6
1304.3
1739.1
MCCB
rated
current
(A)
40
75
100
125
175
200
250
350
500
700
1000
1400
2000
2500
Three-phase circuit
Capacitor
rated
current
(A)
12.6
25.1
37.7
50.2
62.8
75.3
100.4
125.5
188.3
251.0
376.5
502.0
753.1
1004.1
MCCB
rated
current
(A)
20
40
60
75
100
125
150
200
300
400
600
800
1200
1500
Capacitor rating
kVA
5
10
15
20
25
30
40
50
75
100
150
200
300
400
µ
F
99
199
298
398
497
597
796
995
1492
1989
2984
3979
5968
7958
Single-phase circuit
Capacitor
rated
current
(A)
12.5
25.0
37.5
50.0
62.5
75.0
100.0
125.0
187.5
250.0
375.0
500.0
750.0
1000.0
MCCB
rated
current
(A)
20
40
60
75
100
125
150
200
300
400
600
800
1200
1500
Three-phase circuit
Capacitor
rated
current
(A)
7.2
14.4
21.7
28.9
36.1
43.3
57.7
72.2
108.3
144.3
216.5
288.7
433.0
577.4
MCCB
rated
current
(A)
15
30
40
50
60
75
100
125
175
225
350
500
700
900
c) 400V, 50Hz Circuit
Basically, overcurrent leads to excessive tempera-
ture rise of the thyristor junction, resulting in loss of
the control function, and thermal destruction. A fault,
therefore, must be interrupted as quickly as possible,
before the junction temperature rises above its speci-
fied limit. In the overcurrent region, designated on the
current-surge withstand curves of the circuit element,
the element can usually withstand the surge for at
least one cycle. The current-surge withstand, gener-
ally specified as a peak value, must be converted to
RMS, to select a suitable MCCB.
An overload of short-circuit proportion, either ex-
ternal or in a bridge-circuit thyristor element, necessi-
d) 400V, 60Hz Circuit
Capacitor rating
kVA
5
10
15
20
25
30
40
50
75
100
150
200
300
400
µ
F
83
166
249
332
414
497
663
829
1243
1658
2487
3316
4974
6631
Single-phase circuit
Capacitor
rated
current
(A)
12.5
25.0
37.5
50.0
62.5
75.0
100.0
125.0
187.5
250.0
375.0
500.0
750.0
1000.0
MCCB
rated
current
(A)
20
40
60
75
100
125
150
200
300
400
600
800
1200
1500
Three-phase circuit
Capacitor
rated
current
(A)
7.2
14.4
21.7
28.9
36.1
43.3
57.7
72.2
108.3
144.3
216.5
288.7
433.0
577.4
MCCB
rated
current
(A)
15
30
40
50
60
75
100
125
175
225
350
500
700
900
the fault is in one of the thyristor elements, resulting
in reverse current, the result is often that other circuit
elements will be destroyed (see Fig. 7.14) if the cir-
cuit is not interrupted immediately. In this case AC-
side protection or protection in series with each ele-
ment is necessary.
2. Tyristor Overcurrent Protection
Total protection of each element is possible in theory,
but in practice overall coordination and the best com-
promise for economy are usually demanded. Where
elements are critical, complex combinations of pro-
tective devices can be employed, at proportionally
higher cost.
Notes: 1. The MCCB rated current should be approx. 150% of the capacitor rated current.
2. The MCCB short-circuit capacity should be adequate for the circuit short-circuit capacity.
