Re: breaking capacity of breakers

Home Electrical Engineering Forum General Discussion breaking capacity of breakers Re: breaking capacity of breakers

Spir Georges GHALI

nani said:

i need some help on breaking capacities on mcb, about 16ka and 85 ka..can you pls. guys, give some idea about it..tnx

can i replace 16 kA to 85 kA? what is the effect on it..

Dear Nani ;


The ” Breaking Capacity ” for a Circuit Breaker means :

– The CB should withstand a certain value of short circuit current during a time, and the CB is able to trip this short circuit current without any damage on his components.


Normally, to select the value of Breakaing Capacity for any CB, we should know the value of the maximum short circuit current ” Isc3max ” in the place of CB's installation, that means a short circuit current between 3 phases with or without neutral, this value can be knowing by doing the calculation of all Short Circuit Currents. for exp. if this value is ” Isc3max = 13.5 kA ” the value of the relative CB should be bigger than this value that means 16 kA


You can replace any CB by another CB with bigger breaker capacity but not vise vera, and in the same time when the breaking capacity be bigger the CB will be more costly.