What is MCB and How to Calculate MCB Rating? What is MCB? MCB stands for Miniature Circuit Breaker . It is an automatic electrical safety device used to protect a circuit from overload and short circuit . In simple words: MCB is an automatic switch that turns OFF when current becomes too high. It works like a fuse, but instead of melting, it can be reset . Why is MCB Important? MCB protects: Electrical wiring from overheating Appliances from damage Human life from electric hazards Buildings from fire risk That is why MCB is used in every modern house and industry. Types of MCB (Based on Tripping Curve) Type Application ...