An essential safety feature in your home, circuit breakers circumnavigate electrical injuries and fires. What does a circuit breaker do? A mystery to most, these electrically-powered marvels detect and stop excess current in its tracks. They typically trip when there is an overloaded or short circuit, cutting off current to the problem line until the issue can be safely addressed.
What Is the Function of a Circuit Breaker?
In its simplest form, a circuit breaker is an automatic circuit protection system. Breakers are installed in an electrical panel (breaker box) and each circuit is attached to a singular breaker.
Your home’s electrical service panel contains a series of lever-operated circuit breakers that control protect the circuits. Each circuit breaker is designed to ‘trip,’ or shut itself off, at predetermined amperage loads, hence the different size breakers in the box. To protect your home and family against fire and electrical injury, if this limit is reached, the act of the breaker tripping opens the circuit and prevents the flow of current to that particular electrical line or circuit.
Think about a home outlet with a space heater, a television, and a vacuum all plugged into it. This would almost certainly cause a breaker trip, which will shut off access and operation of that circuit until the problem is fixed and the breaker is reset and placed back into position.
Working Principle of Circuit Breakers
Internally, circuit breakers are basically made up of pairs of metallic contacts, both fixed and moving, in addition to an operating coil.
Under normal conditions – closed circuit – these contacts are touching each other, allowing the flow of electric current. These moving contacts are held together thanks to mechanical pressure exerted by another mechanism – a spring or compressed air, for example.
This pressure on the moving contacts is possible thanks to the potential energy stored in the mentioned pressure mechanism. When an overload occurs in the electrical circuit, the operating coil is charged with energy and a plunger connected to the mechanism of the moving contacts, allows the energy stored in this mechanism to be released, allowing the moving contacts to separate as well.
As the moving contacts separate, the circuit inside the CB (circuit breaker) opens, interrupting the flow of current and protecting the system from further damage.
However, it is important that you also understand the concept of “arc”.
When electrical current passes through an air gap from an energized component to a neutral component, a plasma discharge known as arc occurs. As an example, lightning is a very large arc, crossing atmospheric space from a cloud to the ground or to another cloud.
Arcing can also occur in household electrical wiring, but also within circuit breakers during operation, which can damage them and cause fires if the arc is not controlled.
Therefore, the mechanism of circuit breakers also seeks to prevent or control, as much as possible, the generation of these electric arcs.
Most Common Reasons Circuit Breakers Trip:
An overloaded circuit, such as a battle of the dueling hair dryers between mother and daughter, or your annual Christmas light show.
A short circuit, such as a wiring issue within an appliance that results in excess current being pulled.
A ground fault, which typically occurs in high moisture such as the kitchen and bath, and the reason GFCIs are required by current electrical code for your protection.
How Does a Breaker Differ from a Fuse?
Fuses and breakers serve the same purpose overall, though breakers in many cases have overtaken fuses in use (these is not always the case, of course, as fuses still see niche use in many appliances and commercial applications, but it does represent the majority of situations).
The primary difference between a fuse and a breaker is that a breaker can be reused until it wears out, which tends to take quite a bit of time. A fuse, on the other hand, can only be used once. Fuses are a glass cylinder that contains a thin filament, and when tripped, the filament will burn off, melt, or otherwise become useless, and in some cases, the glass cylinder may even crack.
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