What is a Fuse -Working Principle , Function and Types (2024)

A fuse is a small electrical safety device that plays a crucial role and operates to provide overcurrent protection of an electrical circuit, thus ensuring safety and preventing appliances from damage. An important component of an electrical fuse is a metal wire or strip that melts when excess current flows through it, therefore a fuse wire is chosen such that it has a low melting point.
In this article we will be going through what are fuses, the electrical fuse diagram, the fuse working principle, electric fuse characteristics, and Types of Fuses, Next we will go through a Comparison Between AC and DC Fuses, At last, we will conclude our Article with Difference Between a Circuit Breaker and a Fuse, Advantages, Disadvantages, Applications and Some FAQs.

Table of Content

  • What are the Fuses?
  • Electrical Fuse Diagram
  • Fuse Working Principle
  • Characteristics of Fuses
  • Types Of Fuses
  • AC Vs DC Fuses
  • Types of AC Fuse
  • Function of Fuse
  • Circuit Breaker Vs Fuse
  • Applications of a Fuse
  • Advantages and Disadvantages

What are the Fuses?

A fuse is a type of electrical component used to safely open circuits under unusually high current loads, therefore protecting electrical circuits. We can say, that it is a safety device that protects against the overflow of current in an electrical circuit.

A metal component included in fuses is intended to convey a restricted amount of electrical current. The increased current produced by a short circuit or overload will burn the fuse element and leave a gap in it because of the heat it produces. The circuit’s current flow is interrupted by this gap. It operates on the heating effect of the current theory.

The elements used to design the fuse are aluminum, silver, zinc, and copper. The following diagram shows the symbols of an electrical fuse used:

What is a Fuse -Working Principle , Function and Types (1)

Electronic Symbols of a Fuse

Electrical Fuse Diagram

Mostly elements like zinc, aluminium, copper and silver are used for construction of fuses. They are connected in series with the equipment need to be protected or circuit.

The construction of a fuse is simple and typically consists of:

  • Fuse Element: Its a metallic wire that melts when subjected to excessive amount of current..
  • Fuse Body : The fuse element is enclosed by the fuse body.
  • Fuse Caps or Terminals: These are end metallic terminals of a fuse that connects the wire.
  • Fusible Link (in some cases): A wire designed to melt quickly for circuit interruption.
  • Blowout Vent (in some cases): A vent to release pressure in high-current or high-voltage fuses.

What is a Fuse -Working Principle , Function and Types (2)

An Electric Fuse

Fuse Working Principle

An electric fuse operates on the heating effect of current theory and follows that current flows in a loop and if there is a break in a loop ,electric charges cannot flow through it . Electric Fuse is made up of thin metallic wire which is non-flammable and has low melting point. When excessive amount of heat is passed through the fuse, it melts down which leads to opening of circuits and the blockage of current . The melted fuse then can be replaced with new one. Basically , if large amount of electricity flows through a fuse (larger amount of electricity than the capacity of the fuse to bear), it heats up so much that it starts to melt.

Fuse is normally made up of zinc, Aluminium, copper and silver. A fuse is a circuit breaker that cut the power supply when fault occurs. It acts as a shield for Electric appliances and also a safety measure for humans.

Characteristics of Fuses

The following crucial factors need to be taken into account while choosing appropriate fuses:

  • Voltage Rating: Voltage rating are taken into consideration for environmental and circuit safety. Fuse specifications therefore include the highest voltage that the fuse is capable of receiving.
  • Current Rating: This represents current carrying capacity of fuse under standard temperature and conditions. Only fuse will get damage by rapid rise in current.
    Current Circuit = 75% of Current Rating of Fuse
  • I2T Value of Fuse: The product of square of the current in the circuit should be less than I2T value of the device.
  • Temperature: The operating temperature of the fuse is directly proportional to its current capacity.
  • Response Characteristic – It refers to how a fuse behaves in response to overcurrent conditions. Common response characteristics for fuses include: Quick-Acting, Time-Delay, Medium Time-Delay and Very Fast-Acting.
  • Packaging Size: The packaging size of a fuse refers to the physical dimensions and shape of the fuse, it is essential when selecting a fuse for a particular application to ensure that it fits correctly and functions properly .

Types Of Fuses

Depending on the voltage supply , fuses are mainly classified into two types –

  • AC fuses
  • DC fuses

The classification chart is given below:

What is a Fuse -Working Principle , Function and Types (3)

Classification of Fuses

DC Fuses

Dc Fuse is a important component designed for Direct current electrical Systems. It is used to provide protection against overcurrent Situations .Dc fuses are designed to handle unique characteristics of dc current. They are constructed with the materials that are suitable for interrupting DC currents.They typically consist of a fusible element made of a material that melts or vaporizes when subjected to excessive current flow. DC fuses are commonly used in various DC electrical systems, including automotive, marine, solar power, battery charging, and industrial applications. They provide critical protection to equipment and wiring in these systems.DC fuses faces distinct challenges as DC fuses are available in larger sizes and have a constant value over ‘0’ volts, deactivating and removing the circuit can be a little more difficult. There’s a potential that an electric arc will form between the melting wires. In order to eliminate this, a few electrodes are placed farther apart.

AC Fuses

Ac Fuses are the important Components in the Alternating Current System. It helps to protect the circuit from the overcurrent conditions. Unlike DC fuses, AC fuses are made to interrupt the flow of alternating current, which periodically changes. These are made from element designed to melt or vaporize when subjected to excessive current flow.

Comparing the AC and DC fuses side by side, the AC fuse is smaller and oscillates between 50 and 60 times per second, from lowest to highest. Consequently, the possibility of an electric arc forming between the melted wires is eliminated. They can therefore be packed in small sizes. AC fuses are divided into low voltage and high voltage fuses.

Comparison Between AC and DC Fuses


Ac Fuse

DC Fuse





Designed to stop Ac Current

Designed to stop Dc Current


Residential, Commercial, Industrial

Automotive, marine, solar power, industrial


Typically up to 600 volts AC

Wide range, including high voltage DC


Must handle rapid changes in current direction

Must handle continuous direct current flow


Protects appliances, machinery, electrical systems

Protects battery charging circuits, inverters, electrical systems


Easier due to the absence of sustained arcing

More complex due to potential for sustained arcing

Types of AC Fuse

The types of AC fuse are given below:

  • Low Voltage Fuse
  • High Voltage Fuse

Low Voltage Fuses

They are mainly divided into 5 types:

  • Rewireable Fuses
  • Cartridge Type Fuses
  • Dropout Fuse
  • Striker Fuse
  • Switch Fuse

The following categories are discussed below in detail:

  • Rewireable Fuses : These are primarily utilized for home wiring or minor current circuits. The two primary components of a rewirable fuse are the fuse caseand the fuse carrier. The porcelain fabricatedbase offuse is used to contain the wires, which can be composed of lead, aluminum, tinned copper, or a tin-lead alloy.
  • Cartridge Type Fuses: The fuse element contains metal contacts on both sides and is completely enclosed in an enclosed container. Theyaredivided into D-type and Link-type cartridge fuses.

Types of Cartridge Type Fuses

  1. D-Type Cartridge Fuses : The base, cartridge, adapter ring, and fuse cap are the components that make up a D-type fuse. The fuse base is linked to the fuse cap, which holds the cartridge. When the cartridge is fully fitted to the base, the tip meets the conductor, completing the circuit through the fuse connections.
  2. Link Type Cartridge Fuse : The fuse element’s current flow is given under standard conditions in this fuse. Porcelain, ceramic, and silver are used in the fabrication of the regulated arc created when a fuse blows. Silica sand is crammed into the fuse element’s container. These are divided into bolted and bladed fuses.
  • Dropout Fuse: The fuse element falls off of its bottom support due to gravity as the fuse melts. Transformers outside are protected by this kind of fuse.

What is a Fuse -Working Principle , Function and Types (4)

Dropout Fuse

  • Striker Fuse : It’s a mechanical device that can be used to close indicator/tripping circuits since it has sufficient force and displacement.
  • Switch Fuse: In essence, a metal switch and a fuse are encased in a switch type fuse. Low and moderate voltage levels are the principal applications for these fuses.

High Voltage Fuses

These fuses have special design. They are classified into 3 types:

  • Cartridge Type HV HRC Fuse
  • Liquid Type HV HRC Fuse
  • Expulsion Type HV Fuse

Cartridge Type HV HRC Fuse

The helix-shaped fuse componentprevents the effect ofcorona from acting at higher voltages. It consists of two fused parts that are parallel to one another: low resistance and high resistance. Throughout the fault condition, the low-resistance wires both accept the normal current that blows out and reduce the short-circuit current.It is a type of fuse designed for high voltage applications. It is a High Rupturing Capacity (HRC) fuse, meaning it can safely interrupt high fault currents without causing damage.

Liquid Type HV HRC Fuse

Carbon tetrachloride is put into this fuse and is kept intact at both cap tips. The fuse blows out when the error happens, which happens when the current running through it exceeds the permitted limit. For the HRC fuse types, the fuse’s fluid serves as an arc extinguishing standard. They could be employed to safeguard both the transformer and the breaker circuit’s support protection.

What is a Fuse -Working Principle , Function and Types (6)

Liquid Type HV HRC Fuse

Expulsion Type HV Fuse

It is a type of fuse designed for high voltage applications. It is called “expulsion type” because it operates by expelling arc gases to extinguish the arc formed during a fault condition. These fuses are typically used in medium to high voltage electrical systems to protect equipment and circuits from overcurrents.Due to their low cost, expulsion type fuses are frequently employed to protect transformers and feeders. These fuses consist of an open-ended, hollow tube composed of paper bound with synthetic resin.

Function of Fuse

Some of the main functions of fuse are as follows:

  • The fuse prevents short circuits from occurring.
  • It safeguards against device failure resulting from faulty circuit operation.
  • The electric fuse acts as a protective barrier between the electrical circuit and the human .
  • It helps prevent overloads and blackouts.
  • The fuse safeguards against damage caused by mismatched loads.

Difference Between a Circuit Breaker and a Fuse


Circuit Breaker

Works on the thermal and electrical properties of the conducting materials.

Works on the switching principle and electromagnetism.

Fuses cannot be reused.

Circuit breakers can be reused over and over again.

Low Cost

High Cost

Safety measures are limited.

Can offer advanced safety features like ground fault protection and arc fault detection.

It provides both detection and interruption process.

Circuit breaker performs only interruption. Faults are detected by relay system.

Completely automatically.

Manually as well as automatically operated.

Common in basic electrical systems and electronic devices.

Used in residential, commercial, and industrial settings, especially where advanced protection and control are needed.

Applications of a Fuse

Some applications of various types of fuses are :

  • All electrical accessories like laptops, cell phones, printers, scanners have a fuse.
  • All automobiles, including cars, trucks, trailers, boats, etc., use fuses.
  • Power transformers employ high-voltage fuses.
  • Gaming console also finds great use of fuses.
  • Components like capacitors, power converters, motor starters, and transformers make good use of fuses.
  • LCD monitors and battery packs contained fuse in them.

Advantages and Disadvantages of Fuse

There are some list of Advantages and Disadvantages of Fuse given below :

Advantages of Fuse

  • Compact Size: Due to their compact size, fuses can be installed inside of electrical equipment or in Tight Spaces.
  • Cost-Effective: Fuses are Cost-Effective compared to other protective devices such as circuit breakers, making them a cost-less solution for overcurrent protection.
  • Fast Response Time: Fuses provide quick protection against electrical defects by rapidly interrupting circuit current in the case of an overcurrent condition.
  • Low Maintenance: Fuses do not require regular maintenance or servicing, reducing operational costs and ensuring hassle-free operation once installed.

Disadvantages of Fuse

  • One-Time Use: Fuses are designed as one-time protection devices. Once they have operated and interrupted the circuit, they must be replaced with a new fuse.
  • Replacement Time: When a fuse blows due to an overcurrent event, it requires some time to identify the fault, replace the fuse, and restore power to the circuit. This downtime can result in operational disruptions and inconvenience.
  • Limited Protection Range: Fuses have specific current ratings, and they only provide protection within that range. They may not be suitable for applications with varying or unpredictable currents.


In this article, we’ve gone in-depth on the device called fuse. Fuses are silent protectors in the world of electricity, guarding against over currents and potential disasters. They find applications in homes, cars, industries, and various electrical systems. Understanding their types and choosing the right one is vital for safety. Fuses may be small, but their role in preventing electrical hazards is Crucial.

FAQs on Electrical Fuse

Which fuse is used in house wiring ?

Rewireable type fuses are low voltage type fuses. They are used in house wiring and small industries. These fuses have a fuse base within and out terminal and a fuse carrier to hold the fuse element.

What is immaterial for an electric fuse ?

Length is immaterial for fuse wire because melting of a fuse wire is independent of length of fuse wire.

Which material is used for making Electrical Fuses ?

A fuse is a piece of wire with a low melting point material for breaking when the temperature becomes higher than its melting point. Tin, lead, or zinc are the materials used for making fuses.



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What is a Fuse -Working Principle , Function and Types (2024)


What is a Fuse -Working Principle , Function and Types? ›

A fuse is a type of electrical safety device that is used to protect electrical circuits from overcurrents and short circuits. It works by breaking the circuit when a current higher than the fuse's rated current passes through it, thereby preventing damage to the circuit and any connected devices.

What is the principle of a fuse? ›

Electric fuse works on the principle of the heating effect of electric current. It is placed in series with the device. A fuse consists of a piece of wire made of a metal or an alloy of an appropriate melting point, for example, aluminum, copper, iron, lead etc.

What is a fuse and its function? ›

An electric fuse is a safety device which limits the current flowing in an electric circuit. When the current in the circuit increased beyond the limit, fuse burns and it saves different electrical appliances.

What is the function of circuit and fuses? ›

Fuses and circuit breakers act as a safety mechanism that will automatically shut off the current flowing through an individual circuit in order to prevent potential fires and other electrical hazards. Each electrical circuit in a building can only safely handle a certain electrical load.

What is the rule of a fuse? ›

Fuses are always connected in series with the component(s) to be protected from overcurrent, so that when the fuse blows (opens) it will open the entire circuit and stop current through the component(s).

What is the major function of a fuse? ›

The primary use of an electric fuse is to protect electrical equipment from excessive current and to prevent short circuits or mismatched loads. Electrical fuses play the role of miniature circuit breakers. Apart from protecting equipment, they are also used as safety measures to prevent any safety hazards to humans.

What is a fuse very short answer? ›

A fuse is a service that delivers usable electrical circuit over-current safety. Some of the main fuse functions are as follows: Acts as a barrier between both the human body and the electric circuit. Inhibits system failure due to defective operation of circuits.

What is a fuse for dummies? ›

Fuses (also known as fuse links) are an electrical circuit protection device that is designed to blow when too much current flows through it. When the fuse blows it interrupts the flow of current through the circuit.

How to tell if a fuse is fast or slow? ›

The rating of a fuse is always preceded by a letter on the metal casing. For example:T250ma or F210maThe “T” stands for “timed blow” (slow blow), and the “F” stands for “fast blow”.

Why use fuses instead of circuit breakers? ›

Fuses can be more reliable over time, because they do not have moving parts. Fuses do not require regular maintenance. Molded Case Circuit Breakers and others, do. Because a fuse is replaced every time after an overcurrent trip, the same level of circuit protection performance is guaranteed.

Can fuses go bad without blowing? ›

Sometimes a fuse is bad but not necessarily blown. In this case, the best way to test it is with a test light or a multimeter. These are both relatively inexpensive tools and provide an easy way of checking if there's a current running through the fuse.

What is the main purpose of a fuse? ›

A fuse is an electrical safety device that protects an electric circuit from excessive electric current. Fuses are destroyed during overload conditions.

Which operates faster, a circuit breaker or a fuse? ›

Circuit breakers offer faster response times, resettable operation, and more precise protection settings, but they are generally more expensive. The choice between fuses and circuit breakers depends on factors such as the application, budget, and desired level of protection.

How many volts is considered high voltage? ›

The International Electrotechnical Commission and its national counterparts (IET, IEEE, VDE, etc.) define high voltage as above 1000 V for alternating current, and at least 1500 V for direct current.

What makes a fuse work? ›

What does a fuse do? A fuse protects a system or equipment from overload and short-circuit faults by cutting off the power to them. It achieves this by melting or vaporising of the fuse element so that there is no physical connection conductive path for the current flow through.

What is the law of electric fuse? ›

Fuse law determines the current carrying capacity of a fuse wire. The current carrying capacity is directly proportional to (diameter) At steady state conditions, the fuse carries an average current without increasing its temperature to the melting limit.

How does a basic fuse work? ›

If more electricity flows through a fuse than it was designed for, the fuse heats up so much that it melts. This opens a gap in the circuit, which stops the flow of electricity and protects the more expensive components from damage.

What is fuse theory? ›

An electric fuse operates on the heating effect of current theory and follows that current flows in a loop and if there is a break in a loop ,electric charges cannot flow through it . Electric Fuse is made up of thin metallic wire which is non-flammable and has low melting point.


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