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Circuit breakers are a very effective way to protect our cables within an installation. Its a common misconception that there installed to protect people, but in fact there installed to protect out cables.

There are three types of circuit breakers : Thermal circuit breaker, Magnetic circuit breaker and a Thermal/magnetic circuit breaker.

The thermal type circuit breaker works by means of a bimetallic strip. This is a piece of metal that is constructed of two dissimilar (different) metals stuck side by side. When this strip has current passed through it, one side of the metallic strip heats quicker than the other, causing the metallic strip to bend in one direction. (Heat is a byproduct of current passing through a conductor). The bimetallic strip is connected to the trip mechanism and in in turn will open the circuit breaker. Thermal circuit breakers are best at protecting over loads rather than short-circuits due to there slow reaction time. The pictures below demonstrate their operation