Difference between Fuse and Circuit Breaker: Definition, Structure and Function

The electrical circuit is an interconnection of electrical components in order to perform a specific function. These circuits use two types of power, alternating current and direct current. The power may increase or decrease suddenly when this current is flowing through devices. Fuse is a safety device in the form of a wire which is present inside an electrical circuit. This wire melts immediately and stops current flow as soon as it detects a fault like current overload. Circuit breakers are electrical switches designed to protect the electrical device from short circuits. They can be found everywhere, starting from households to industries. There is a huge point of difference between the two. Let us take a closer look at them. 

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What is a Fuse?

Fuse basically sounds like the powerhouse or the center place of all the electrical circuits of the house in one single box. In simple terms, a fuse can be defined as an electrical safety device responsible for regulating the current in the entire electrical circuit. A fuse holds a very important place in electrical engineering. It is solely concerned with the function of providing or distributing an equal or required amount of current. 

The fuse can be actually called as a backup. For example, if the wires get heated enough and start running excessive current, ending up producing a lot of heat energy, the fuse can be utilized to remove the power from such a faulty system. 

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Structure of a Fuse

A fuse is made up of a metal strip placed between a pair of electrical terminals. It is covered by housing which is non-combustible in nature. The fuse must carry the current efficiently all the way through the protected circuit, which is why it is arranged in the manner of a series. As current flows, heat is produced by the resistance of the element. When a high current starts flowing, the temperature of the element rises. This results in the melting of the element itself or the melting of a soldered joint inside the fuse. The fuse element can be zinc, copper, silver, or aluminum. The heating effect depends upon the shape of the fuse element. Current is divided between multiple strips of the metal element. Some outside materials may be used as a catalyst to speed up the quenching of the arc. This may be the air that surrounds the fuse element or even silica sand. 

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Functions of a Fuse

A fuse is associated with the following functions:

• A fuse is responsible for preventing short circuits
• Acts as a barrier between the human body and the circuit
• The fuse prevents a device from breaking down due to short circuits
• Fuse keeps any kind of blackouts from happening

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What is a Circuit Breaker?

A circuit breaker is an electrical switch solely concerned with protecting an electrical circuit from any kind of damage. This damage may be caused by current overload or a short circuit. It has the ability to be operated both by manual means and automatically. It stops the current flow as soon as it detects any fault. It need not be replaced completely after a fault and can be reset to normal working. 

Circuit breakers come in different sizes. The small ones are restricted to a single household while the larger ones are responsible for controlling the current of an entire city. The idea of circuit breakers came a little later after Thomas Alva Edison invented the light bulb back in 1879. 

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Structure of a Circuit Breaker 

There are different types of circuit breakers like a vacuum circuit breakers, air circuit breakers, molded-case circuit breakers, etc. Molded-case circuit breakers are very commonly used in the case of low voltage circuits. The economic cost and the sizes of these circuit breakers are what makes it so promising. The important components of this circuit breaker are 

• frame/molded case
• Operating mechanism
• Arc extinguisher 
• Trip units 

The frame of this circuit breaker serves as an insulated cover mounted at the top to cover all the components of the machine. The material of this frame may be glass polyester or resin. Different sizes of circuit breakers have different frame designations. 

The operating mechanism of a circuit breaker is responsible for the opening and closing of contacts. Upon holding the handle in the on position, the breaker is bound to trip. Therefore the position of the handle implies the state of the contacts. It may be closed, open, or tripped depending upon the handle movement. 

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When the circuit breaker stops or disturbs the current flow due to faults, an arc is created. This arc extinguisher must divide the arc by extinguishing it for smooth functioning. These extinguishers are made of a stack of steel plates. There are two insulator plates present which hold this stack in position. Trip init can be called the engine of the whole circuit breaker. When a short circuit takes place, the trip unit trips the operating mechanism. These trip units provide protection to a great extent against short circuits, overloads, and arcing ground faults. 

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Function of a Circuit Breaker

A circuit breaker serves two primary functions. These are:

• The basic function of a circuit breaker is to prevent any further supply of current as soon as it has detected any fault or overload. It immediately stops the current flow. 
• When the fault has been rectified, the circuit breaker resumes the normal flow of current again. 

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Difference between a Fuse and a Circuit Breaker

The major differences between a fuse and a circuit breaker are as follows:

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Things to Remember 

• A fuse is a safety device responsible for controlling the flow of current. It is the center point of all the electrical circuits in the house which is why it is very important in electrical engineering. The material of the fuse element may be zinc or copper. 

• A fuse is associated with the function of stopping the current flow in situations like current overload, and short circuits. They also serve as a protection of the human body from such circuits, preventing blackouts and mishaps. Fuses also prevent the device from failing completely because of such faults. 

• Fuses have an operating time of about 0.0002 seconds. They don't provide any indication at the time of overload but are automatic in nature. They have a low breaking capacity and are extremely affordable. However, once used, a new fuse has to be used or installed. 

• A circuit breaker is an electrical switch that protects the electrical circuit from being damaged. They can be handled either manually or automatically. After stopping the current flow during a fault, it has the ability to reset the device back to normal working mode. 

• Circuit breakers have a high operational cost and work on the principle of electromagnetism. They always give an indication in case of overloads and operate for about 0.02-0.05 seconds. Circuit breakers have a high breaking capacity. A molded-case circuit breaker is a very common type of circuit breaker used by people.

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