Please study these data a little more carefully. They are not 3K, 6K & 10K. They are 3kA, 6kA & 10kA respectively. They are the breaking capacities of the MCBs. It implies the maximum amount of current that the MCB can safely break (or open) without causing any damage to itself or to the installation or to the operator.
The selection depends upon the maximum fault level at the point of installation of the MCB.
The only factor is the fault current at the point of installtion of the MCB. You should know how to calculate fault currents at various points in the network. Then only you can select the breaking capacity of the MCBs correctly.
MCB Construction
Re: MCB CONSTRUCTION
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