Answer to Question #116949 in Electric Circuits for James

Question

how do fuses and miniature circuit breakers (MCB’s) work in domestic appliances and why are they necessary?

Answer 1

MCB is mainly used to protect your device from an overload current in case of some internal short circuit fault in your device. Fuse is also designed for machine protection and will trip only if the current exceeds the fuse rating.

Explanation:

MCB offers protection against overload. Overload means an excess current drawn, which will lead to tripping of the circuit breaker once the current exceeds 5 times the rated MCB current value within a tenth of a second (depending on the Type of MCB).

When your electric load is faulty and there's a short circuit, a lot of current is drawn -> MCB trips. But an electric shock to a human being may not always draw an excessive current that is so high to trip the MCB and protect you.