MCB - Miniature circuit breakers

Within half a millisecond (ms) a short-circuit is released, the coil registers the increased current due to the fault. The hammer trip forces the contacts to open.

The unequal pressure across the arc causes the plasma wave to be driven away from the contacts into the arc extinguishing chamber.

In less than 3 ms after the short circuit current is released, the fault is safely cleared. Due to its mass inertia, it takes the toggle 10 ms to reach its end position.

In overload tripping, excessive current heats up a strip made up of two metals, called a bimetal.

When the current exceeds the rating of the MCB, the bimetal bends and eventually trips the MCB. Depending on the intensity of the current, this may happen after seconds or even minutes.