What is an Electric Fuse?
An Electric Fuse is an Electric device which interrupts the flow of current in an Electric circuit. It is installed in a circuit to stop the flow of excessive current. A Fuse is usually a short piece of wire. The Fuse is made up of a material which has high resistivity and low melting point, so that it melts down due to overheating of the wire during high current flow.
The thickness of the Fuse wire is determined based on the amount of current flow in the circuit. Normally an alloy of tin and lead is used as the Fuse wire, as it has high resistivity and low melting point.
If a fault causes a flow of excess Current then a thin Conductor is used to break the Circuit by melting or separating it, the thin Conductor used is known as an Electric Fuse. A Fuse can be sacrificed if anything in the Circuit goes wrong since they are weak points that are intentionally placed in a Circuit. For example, in order to protect the wiring of the vehicles, a Fuse panel is placed near the batteries of the Car.
The wire inside the Fuse melts if there is an occurrence of high Current due to a short Circuit or an overloaded Circuit. As a result of which the Current stops flowing since the wire has broken. In order to stop the flow of Electricity, the Electric Fuse gives up its life. There is a clear plastic window in some Fuses from which one can check if they are still good.
Electric Fuse- Working Principle
The Electric Fuse works on the basis of the heating effect of the Electric Current. It is composed of a non-flammable thin metallic wire with a low melting point.
If a high amount of Electricity is passed from the Electric Fuse, there is a production of heat which causes the Fuse to melt which leads to the opening of the Circuit and the blockage of Current.
Once a Fuse melts, it can be changed or replaced with a new Fuse.
A Fuse is normally made up of elements like zinc, copper, aluminum and silver.
A Fuse acts as a circuit breaker and breaks the circuit in case any fault occurs in the circuit. It acts as a protector of Electric appliances and also as a safety measure for humans. The figure below represents a Fuse operation, Fuse barrel and Fuse link.
Characteristics of an Electric Fuse
Here are some important characteristics of a Fuse wire.
Current Rating: It is defined as the continuous conduction of maximum current holded by the Fuse without melting. It is the capacity of current, and is measured in Amperes. Current (Cin)=75% current (rating)
Voltage Rating: If voltage is connected in series with the Fuse, it does not increase voltage rating.
Hence,
V (Fuse) >V (open circuit)
I2t Rating: It is the total energy which is carried by the Fuse element in case of a short circuit. It measures the heat energy of the Fuse, and is generated when the Fuse breaks out.
Interrupting or Breaking Capacity: The maximum rating of current without harming the interruption by the Fuse is known as interrupting capacity of the Fuse.
Breaking capacity > maximum rated voltage
Breaking capacity < short circuit current
Voltage Drop: The Fuse element melts whenever there is an excessive current in the circuit, and opens the circuit. Due to this, voltage drop and resistance change reduces.
Temperature: The Fuse melts when the operating temperature is higher and the current rating is lower.
The graph represents temperature vs current carrying capacity of a Fuse. The current carrying capacity of a Fuse is 100% when the temperature is 25°C (three lines meet at this point). After that the current carrying capacity decreases upto 82% at 65°C. This shows that increase in temperature decreases the current carrying capacity of a Fuse.
Electric Fuses are proven to be helpful in safeguarding any Electrical appliance or household Circuits. Its features are-
The melting points of Electric Fuses are very low, which is 200° C.
Fuse wires are made of an alloy composed of 50% lead and 50% tin.
The resistance of Fuse wires is so high that whenever its temperature rises and it reaches its melting point, it breaks the Current which passes through the Circuit.
Functions of Electric Fuse
Electric Fuses have to give up their lives in order to safeguard the Circuits. Some other important functions of Electric Fuses are listed below-
Restricting the flow of Current- An Electric Fuse acts as a barrier between an Electric circuit and the human body.
Preventing the wires from catching fires or breakdowns- It prevents any damage to the Electric device by restricting excess current flow.
Terminating the Current from the Circuit if a short- Circuit or overloading happens- When too many appliances are connected in a single circuit, it leads to overload which requires a Fuse to terminate the circuit connection.
Prevention from blackouts- if any dis-function occurs in the components of the circuit, the nearest circuit breaks.
Prevention from damage occurred due to mismatched loads.
Information about the ampere rating, voltage rating, approval standards of the Fuse and interrupt rating are generally marked on the Fuse. This information must be checked and verified before buying a Fuse.
FAQs on Working Principle of an Electric Fuse
1. What are the Different Types of Fuses?
Fuses were invented by Sir “Thomas Alva Edison”. Many Fuse types are available in the market. Mainly the two types of Fuses are :
DC Fuses: DC Fuses are large in size. DC supply has a constant value, slightly above 0V. So, it becomes hard to turn off the circuit, thereby creating a chance for an Electric arc between melted wires. To overcome this, electrodes are placed at a larger distance in the Fuse. For this reason the DC Fuse is bigger in size.
AC Fuses: AC Fuses are generally smaller in size. They oscillate around 50-60 times per second from minimum to maximum. No chance of Arc between the melted wires arises. For this reason the AC Fuse is small in size.
AC Fuses are further categorized into two types, i.e., High voltage Fuse and Low voltage Fuse.
High-voltage Fuse- High voltage Fuses are further classified into three types of Fuses which include a thermal Fuse, cartridge type Fuse, and a high voltage liquid Fuse. Thermal Fuses protect Electrical equipment from damage from overheating. The cartridge-type Fuses are used to prevent the corona effects at high voltage and are used in parallel. High voltage liquid Fuses use carbon tetrachloride from arc extinction.
Low-voltage Fuses- Low-voltage Fuses are also classified further into two types: rewirable and cartridge type. The rewirable Fuses are most commonly used in house wiring. The cartridge Fuses are enclosed in containers that are tightly sealed and have a metal contact at both ends. Cartridge Fuses have two types- Link-type of High Rupturing Capacity Fuse and D-link Fuse.
2. What is the Principle of Fuse?
Electric Fuse is based on the principle of heating effect of Electric current. Heat is produced when current flows in the wire. When heat production is more due to excessive flow of current, it melts the Fuse which normally has a low melting point, thereby preventing any damage to the Electric circuit and appliances.
3. What are the Uses of Fuse?
The Fuses are one of the most important parts of an Electric circuit and an electronic system. Here are some uses of a Fuse:
They are used in home distribution boards, Electronic devices and Electric appliances to prevent any damage due to excess current flow.
They are used in gaming consoles and all automobiles like cars, bikes, scooters, trucks and all other vehicles.
They are used in laptops, printers, cell phones, hard disk drives, scanners, and portable electronics.
Fuses are used in capacitors, power converters, transformers, power transformers, motor starters if an Electrical distribution system.
They are also used in LCD monitors and battery packs to stop excessive current flow to the device and prevent it from damage that may occur to electronics.
4. What are the two main parts of an Electric Fuse?
The two main parts of an Electric Fuse consist of a Fuse element as a metal Conductor attached with a pair of contacts and a cartridge or a case that carries the Fuse element. Cartridges are adjusted with arc-extinguishing devices. If there is a short Circuit then the Current flowing through the Fuse element exceeds the prescribed limits which lead to the creation of excess heat that metals the Fuse wire and breaks the Circuit.
5. What are some advantages and disadvantages of an Electric Fuse?
Some of the advantages of an Electric Fuse include-
Electric Fuses are the cheapest available form of protection.
Minimal operating time.
There is not any need for repairs.
Short-Circuits disrupt without any production of gas or smoke.
They work automatically.
Current protection is due to the inverse-time Current characteristics.
Some of the disadvantages of an Electric Fuse are-
It is not always possible that the Current-time characteristic is always correlated with the protection of the device.
A considerable time is taken after the operation in order to replace the Fuse.
6. What are some differences between a Circuit breaker and a Fuse?
The most primary difference between a Circuit breaker and a Fuse is that once a Fuse is melted, it has to be replaced and it gives up its life while in the case of a Circuit breaker it can be reset and used over. Circuit breakers are devices that stop the Current flow as any fault occurs while a Fuse destructs itself whenever the Current exceeds a certain limit. To learn more about Circuit breaker and Fuse differences, students can visit Vedantu’s study material on the difference between a Circuit breaker and an Electric Fuse.
7. What is meant by the term MCB?
Electromechanical devices that are designed in order to protect an Electric Circuit from over-loaded Currents are known as miniature Circuit breakers or MCBs. The three principle characteristics that and an MCB possesses are- Amperes, Tripping curve, and Kilo-Ampere. Unlike Electric Fuses, MCBs do not self-destruct themselves and are replaceable. It is very easy and safer to use MCBs since they offer a convenient on/off switch and the Conductor is encased within a plastic case making them safer to operate.