Product standard BS EN 60947-1 defines the ratio n between the peak value and the rms value of the short-circuit current (table 16 on page 106). The rms value must be taken into account for the thermal effect, and the peak value must be taken into account for the electrodynamic effect. The value of n is:

1.41 for I <= 1500.
1.42 for 1500 < I <= 3000.
1.47 for 3000 < I <= 4500.
1.53 for 4500 < I <= 6000.
1.7 for 6000 < I <= 10,000.
2.0 for 10,000 < I <= 20,000.
2.1 for 20,000 < I <= 50,000.
2.2 for 50,000 <; I.

For information: In the circuit breaker standard BS EN 60947-2, these values (Icu/Icm) are given in table 2 on page 19.

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