Types of Circuit Breaker Guide

What is the Circuit breaker?

The circuit breaker is a crucial component in electrical systems that provides protection from overcurrent and short circuits.

It is a device that automatically interrupts electrical current flow when there is an excess of current or an unexpected surge in voltage.

It acts as a safety mechanism that prevents damage to electrical equipment and helps to minimize the risk of electrical fires.

Understanding its basics is essential for homeowners, electricians, and anyone who works with electrical systems.

In this blog post, we will explore the different types of circuit breakers, their functions, and how they are installed.

Miniature Circuit Breaker

Miniature Circuit Breakers, or MCBs as abbreviated, according to BS EN 60898, are suitable for operation by ordinary persons and have fixed protection settings, generally a two-position on/off operating handle, and a performance relative to the final circuits in an electrical installation.

They would normally be the final overcurrent protection measure in the electrical system, for example, before sockets or lighting circuits.

Typical current ratings are from 0.5 A to 125 A. Short-circuit ratings may be up to 25 kA.

Performance and testing are in accordance with BS EN 60898 for domestic and similar applications, categorized by the trip characteristic types B, C & D.

MCBs may also be available with application-specific tripping characteristics.

MCBs may also be rated in accordance with BS EN 60947-2 for industrial or similar applications.

Summary of MCB:

It has two positions only, ON or OFF.
Its size is small.
It can be single-, double-, triple-, or four-pole.
It has low short-circuit capacities.
It’s not adjustable, fixed only.
Its trip unit type is thermomagnetic.
Its cost is cheap.
We use it in the final circuits, like lighting and power.

Moulded Case Circuit breaker

Moulded Case Circuit Breakers, or MCCBs, may have fixed or adjustable protection settings, normally with a three-position toggle operating handle that provides on-off-tripped indication, a reset function, and a performance level relative to the incoming supply, allowing them to be installed close to the supply transformer.

Typical current ratings range from 16 A to 1600 A; ratings up to 3,200 A are available, depending on the manufacturer’s standards.

Short-circuit ratings may be up to 100 kA. Performance and testing are in accordance with BS EN 60947-2.

Sometimes we use it as the main breaker, or it can serve as the breaker for branch circuits in other panels, like SMDBs & MDBs.

Summary of MCCB:

It has three positions: ON, OFF, or Trip.
Its size is medium.
It can be triple or four poles.
It has medium values of short circuit capacities.
It can be fixed or adjustable.
Its trip unit type can be thermomagnetic or Electronic.
Its cost is not cheap.
We use it sometimes in the branch circuits or as the main breaker in the panel.
It can be motorized or not.

Air Circuit breaker

(ACBs) They are normally used as the main incoming protection and have a spring-operated mechanism to open and close the device, often charged by an internal motor.

The protection settings will include time delays, and the devices will have a short-time withstand value to give full discrimination under fault conditions with downstream protection devices.

Typical current ratings are 630 to 6,300 A. Short-circuit ratings may be up to 150 kA.

Performance and testing are in accordance with BS EN 60947-2.