NEN 1010 §434.5
Breaking capacity
Breekvermogen (Icn / Icu)
Also known as: icn, icu, breekvermogen, breaking-capacity, ka
Maximum short-circuit current an automatic circuit breaker can safely interrupt without damage. Icn = nominal standard for dwellings (6000 A), Icu = ultimate industrial value (10/15/25 kA). Insufficient breaking capacity → breaker explodes during actual short circuit.
Practical example
Breaking capacity (Icn / Icu). In an industrial distribution board with Ik of 20 kA, a circuit breaker with Icu ≥ 25 kA is used instead of the standard domestic Icn of 6000 A.
Common mistake
Breaking capacity (Icn / Icu): Using a domestic MCB (Icn 6000 A) in an industrial panel with higher prospective short-circuit current — the breaker may fail instead of safely interrupting.
See also
Related terms
In-depth guides
- → §537 Power factor correction (cosφ) for heavy motor loads
- → §423 (IEC 60364-4-42) §423 — Protection against burns: maximum accessible surface temperatures (Table 42.1)
- → §712 Solar Power Systems (PV)
- → §722 Electric Vehicle (EV) Charging Points
- → NEN 1010 §729 (gangpaden) Operating and maintenance gangways for switchgear and distribution boards (NEN 1010 §729)
- → IEC 60831-1 / Praktijk (condensatorbanken) Capacitor bank discharge resistor — why a switched-off power capacitor can remain dangerously charged
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