Breaking capacity is the maximum prospective short-circuit current a protective device can interrupt without failing, given in kA at a stated voltage. For low-voltage breakers IEC 60947-2 separates ultimate breaking capacity (Icu) from service breaking capacity (Ics), the level after which the breaker must still work normally. A device installed where prospective fault current exceeds its rating can explode instead of clearing the fault.
Prospective fault at that board is 25 kA and the MCBs are only 10 kA breaking capacity, so they need backup fuses or replacing.
North American electricians say AIC or interrupting rating for the same idea.
Also heard as
- interrupting rating
- interrupting capacity
- AIC
- kAIC
Related terms
Fault current
Abnormally high current that flows when insulation fails and a short circuit or earth fault forms.
Short circuit
Unintended low-impedance path between conductors at different potentials, bypassing the load.
Switchgear
Assemblies of breakers, switches, fuses, busbars and enclosures that control and protect power circuits.