Miniature Circuit Breakers (MCB): Types, Working & Selection Guide

A miniature circuit breaker (MCB) is a resettable safety device that automatically switches off a circuit when the current exceeds a safe level, protecting cables and equipment from overloads and short circuits.

How an MCB works

Inside every MCB, a bimetallic strip responds to sustained overloads while an electromagnetic trip coil reacts instantly to short circuits, cutting power within milliseconds.

Trip curves: B, C and D

• Type B – trips at 3-5x rated current, ideal for lighting and sockets.
• Type C – trips at 5-10x, suited to motors and general commercial loads.
• Type D – trips at 10-20x, reserved for high inrush equipment.

Choosing the right rating

Match the MCB rating to the cable size and load. As a factory-direct manufacturer, Walax supplies MCBs from 1A to 63A with B, C and D curves to suit nearly every installation.