What is the standard breaking capacity (kA) for MCBs?

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Detailed Solution

The breaking capacity (or interrupting rating) is the maximum short-circuit fault current that an MCB can safely interrupt without being destroyed or failing.It is a measure of the MCB's robustness and is measured in kiloamperes (kA).

If a short circuit occurs with a fault current higher than the MCB's breaking capacity, the MCB itself could fail catastrophically (explode or weld shut), failing to protect the circuit. The required breaking capacity is determined by the electrical installation's proximity to the supply transformer.

Standard breaking capacities as per IEC 60898-1 are:

6 kA (or 6000A): This is the most common standard for residential and domestic installations. It is sufficient for most homes and small buildings.
10 kA (or 10000A): This is the standard for commercial and light industrial applications where the available fault current from the grid is higher.
15 kA and higher: These are used in heavy industrial settings with very high potential fault levels.

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