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78
HAVELLS
Miniature Circuit Breakers (MCBs)
Ambient Temperature
Compensation/Diversity Factor Chart
Maximum Permissible Rated Current (K, factor)
Diversity Factor (K, Factor)
Let Through Energy I2t
K
1
Graph 1
-25 -10 0 10 20 30 40 50 60
10A
6A
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
16-32A
40-63A
1-4A
K
Factor
Number of poles placed together with gap in between
1 2 3 4 5 6 7 8 9 10 11
0.6
0.7
0.8
0.9
1.0
Factor
K
2
Graph 2
Calculation I
n
/ MCB = K
1
x K
2
x I
n
Example
4 MCBs with I
n
= 10 A, and the amb. temp. is 50 ˚C kept with no gap in between
Solution
K1 =0.89 (from graph 1) K2 =0.78 (from graph 2)
I
n
/ pole = 0.89 x 0.78 x 10 = 6.94 A