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PowerSafe – Commercial & Industrial
79
Miniature Circuit Breakers (MCBs)
Selection of MCB for Motor Protection
Cold Resistance & Power Loss Details Maximum Backup Protection
1 Phase 230V DOL
Starting
3 Phase 400V DOL
Starting
3 Phase 400V Assisted Starting
Star Delta
S. No.
kW HP
Full Load
Current
MCB
Selection
Full Load
Current
MCB
Selection
Full Load
Current
MCB Selection
C
C
C
D
1
0.18
0.24
2.8
10
0.9
2
—
—
—
2
0.25
0.34
3.2
10
1.2
2
—
—
—
3
0.37
0.50
3.5
10
1.2
2
—
—
—
4
0.55
0.74
4.8
16
1.8
3
—
—
—
5
0.75
1.01
6.2
20
2.0
3
—
—
—
6
1.1
1.47
8.7
25
2.6
6
—
—
—
7
1.5
2.01
11.8
32
3.5
10
—
—
—
8
2.2
2.95
17.5
50
4.4
10
—
—
—
9
3
4.02
20.0
63
6.3
16
6.3
16
10
10
3.75
5.03
24.0
80
8.2
20
8.2
20
10
11
5.5
7.37
26.0
80
11.2
25
11.2
32
16
12
7.5
10.05
47.0
125
14.4
40
14.4
40
25
13
10
13.40
—
—
21.0
50
21.0
50
32
14
15
20.11
—
—
27.0
100
27.0
63
40
15
18.5
24.80
—
—
32.0
125
32.0
—
50
16
22
29.49
—
—
38.0
125
38.0
—
63
17
30
40.21
—
—
51.0
125
51.0
—
63
Rated Current
I
N
(A)
Cold Resistance
I
N
(A)
Power Loss
per Pole
P
v
(W)
1
1178.00
1.3
2
281.00
1.5
4
92.00
2.2
6
16.55
0.7
10
11.68
1.4
13
10.10
1.7
16
8.00
2.2
20
5.25
2.5
25
3.78
3.1
32
2.57
3.4
40
1.94
3.9
63
1.40
7.3
2EMARKS 4OLERANCE ¢
MCB Current Rating
Backup Fuse Rating
1
25
2
35
4
50
6
80
10-63
100