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What is a circuit breaker?

August 9th 2023

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As the name suggests, a circuit breaker is an electromechanical device that protects electrical installations from overload and short-circuit faults by cutting off the power supply.

Like a fuse, a circuit breaker works like an automatic switch with a base current value that switches off whenever said value is exceeded.

However, unlike most conventional fuses, a circuit breaker is reusable.

Siemens SIRIUS Circuit Breakers

When a fuse’s base limit is exceeded, a metal alloy inside the fuse melts, thus interrupting the power supply to the circuit. This reaction is irreversible, unlike in a circuit breaker where a switch will be triggered by a component which can both expand and contract.

Circuit breakers are used everywhere, from residential applications to large industrial applications, and, as a result, there are many different types of circuit breaker, including:

Low-voltage circuit breakers are designed for circuits with 600 volts or lower.

High-voltage circuit breakers are more robust and are designed for 600 volts and higher.

Moulded case circuit breakers (MCCB) contain all their components within an insulated moulded case and are versatile. MCCB frame sizes range from 250 to 2000A, but they can be rated as low as 75A, making them ideal for low-voltage environments. MCCB can also be used in medium-voltage applications such as industrial or commercial control panels and switchboards.

ABB TMax XT Series Circuit Breakers

Miniature circuit breakers (MCB), with their small size, are perfect for isolating electrical components in residential, industrial, and commercial applications. MCB amperage ratings typically range from 2 to 32A and are almost always low-voltage rated.

Vacuum circuit breakers use a vacuum to break the electrical arc, have a lower fire-hazard potential than other circuit breakers and are commonly used within hotels, water treatment facilities and power plants.

Oil circuit breakers use oil as an insulating medium to extinguish arcs and are commonly used in power plants and electrical substations.

These are just a few different types of circuit breaker. Choosing the right one requires careful consideration because for circuit breakers to work correctly, knowing the exact size of the circuit and its components is critical.

If you need help finding the correct breaker or replacing an old circuit breaker, call Foxmere on +44 (0)1922 349 999 or email us at [email protected].

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