What is a circuit breaker?

Circuit Breakers in a Home

A circuit breaker is an electrical switch inside a breaker box that interrupts electrical current in the entire electrical system when it exceeds a safe level which usually happens when wires short circuit. Circuit breakers are designed to protect the other electrical components in the entire electrical circuit from damage by excessive currents. Circuit breakers are usually found in household electrical distribution boards.

Circuit breakers have different characteristics for their protection ampere rating and levels which is dependent on the application they are used for when dealing with the excess current. Some of the common applications of circuit breakers include power generation, distribution and electrical systems in commercial buildings.

A Circuit Breaker’s job is to safely switch off an electrical current when it exceeds a predetermined value without causing damage to any other part of this system. This usually happens due to a short circuit of the wires or ground fault. It’s designed to protect. When a fault occurs within the electric circuit like overloading due to overload or short-circuiting, a maximum amount of electricity will flow through that faulty circuit.

It may cause severe damage if left uninterruptible; therefore a mechanism has to be in place to interrupt it quickly without causing further damage. It does this job by sensing the current flow through it and closing (or opening) its contacts to open the circuit as soon as it exceeds a pre-set value known as trip level.

Circuit breakers are installed by licensed electricians as they require certifications to be met which only licensed professionals can undertake in Australia.

How does a circuit breaker operate?

Circuit breakers operate to interrupt an electric current very quickly, within milliseconds or less than 1 second. They are also used in control circuits that do not use DC power, which cannot be interrupted with a simple switch. Circuit breakers can have time delays that prevent nuisance tripping on voltage sags, and they may or may not have integral thermal overload protection.

There are three main operation mechanisms in a circuit breaker:

  • electromechanical
  • magnetic
  • thermal

Other operations include spring return electrical limit switches and relay logic.

Circuit breakers are manufactured to protect a wide range of electrical applications. They are available in many sizes and ratings, from very small devices rated for less than 3 amperes up to large high-current devices rated at over 100,000 amperes or more. Power levels range from those used on individual circuits inside buildings up to switchgear that serves an entire substation.

Circuit breakers can be installed as single-pole (SP), double-pole (DP), or three-pole (TP) depending on the number of parallel conductors they isolate and the number of phases being protected by each device within the switchgear enclosure. The switching capacity of circuit breakers is expressed in terms of common usage, most often referred to as Maximum Trip Rating (MTR). Trip ratings are the maximum current that the device can interrupt without sustaining damage.

Circuit breakers use a variety of mechanisms to interrupt current. These include:


magnetic trip devices located in air gaps or at points within power conductors, and one method that uses the thermal expansion of metal in response to increasing temperature. This latter type is used for circuit breakers rated over approximately 30 amperes and employs either link-bonded contacts or free-swinging blades made from extruded aluminium or copper alloy alloys.

Circuit breakers larger than 60 amperes often use a combination of magnetic and thermal mechanisms, but not necessarily simultaneously; breaker mechanisms above 100 amperes usually incorporate both magnetic and thermal protection mechanisms.

In the event of a fault current exceeding this value, thermal expansion forces one or more blades to trip and interrupt flow through the circuit breaker. This operation also causes an arc inside the circuit breaker.

The blade is designed to carry enough current to allow it to do its job without causing major heating; however, as soon as the fault has been cleared and currently reduced below trip level, switches in series with each other start to close again by means of springs (or another return mechanism), reducing any residual magnetic force on the contactors holding them open and allowing them to return to their original position ready for operation on future faults.

What is a circuit breaker device?

A circuit breaker is a mechanism that interrupts the current flow in an electric circuit in response to overload or short circuits

Since a breaker’s purpose is to protect the circuit that it is placed on, it should not create any further damage when it trips. The circuit breaker needs to be able to sense the rapid changes in electrical current and close (or open) its contacts within milliseconds

How does a circuit breaker work?

The operation mechanisms of circuit breakers are electromechanical, magnetic, thermo-magnetic, and spring return electrical limit switches.

What is the difference between a fuse and a circuit breaker?

A circuit breaker is a mechanism that interrupts the current flow in an electric circuit in response to overload or short circuits. Since a breaker’s purpose is to protect the circuit that it is placed on, it should not create any further damage when it trips. The circuit breaker needs to be able to sense the rapid changes in electrical current and close (or open) its contacts within milliseconds.

Unlike a fuse that will blow out if there are too many surges of energy/electricity, a Circuit Breaker can detect these spikes and cut them off before they lead to any serious problems with one’s electronics or other devices plugged into an outlet. This helps ensure safety for all parties involved by automatically stopping power from feeding into anything connected while helping eliminate delicate circuitry from burning

How do trip switches work

Trip switches may be classified as either magnetic, thermal, or a combination of both. A magnetic trip device is installed in an airgap or at points within power conductors. The device interrupts the flow of current by means of electromagnetic interaction. This type of switch constitutes the most popular type of trip unit and is often called a ‘magnetic breaker’.

A circuit breaker may be connected to a smart meter to track any circuits that may trip.

A thermal trip device opens by means of the expansion of copper blades, in response to increasing temperature. This type is employed for circuit breakers rated over 30 amperes and can be used with link bonded contacts or free-swinging blades made from extruded aluminium or copper alloy alloys.

In order for larger breakers to work, they require a backup method of protection. This is why in really large power lines, there are often two breakers. One breaker will cut the power when it trips while the other one stays “on.”

Where is the main circuit breaker located?

The main circuit breaker switch is typically located in the service panel or switchboard in a house. This location is important because it prevents the main circuit breaker from being accessed, or operated by unauthorized people. When it comes to electricity, safety should be a top priority.

The main breaker offers protection to the main distribution panel inside of a building or house. The breakers found in your home were designed for specific uses and voltage, such as kitchen outlets and garage outlets.

What does a circuit breaker do?

Circuit breakers protect equipment and people by opening an electrical circuit when too much current flows through it, thus stopping the flow and contact of electricity. When an overload or short-circuit causes too much current to flow through contact points on a circuit breaker, high-tension spring coils expand, releasing their tension instantly so that they are free to close again upon restoration of normal load conditions. This switch happens very fast on modern devices.

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