What Is a Fuse?
A fuse is a safety component believed to have been invented by Thomas Edison over 100 years ago. It is designed to protect electrical devices by breaking the circuit when an excessive current flows through it. When this happens, the fuse melts and stops the flow of electricity, preventing damage to the connected equipment. The primary purpose of a fuse is to prevent risks such as the following:
- Preventing Equipment Damage from Overcurrent: Protects devices from being damaged by excessive electrical current.
- Fire Prevention: Suppresses overheating and ignition caused by overcurrent.
- Comprehensive Circuit Protection: Interrupts the circuit before critical components are damaged.
Excessive electrical current can damage equipment or even cause fires. Fuses are designed to prevent these dangers, making them an essential safety component. Fuses are widely used in various applications, from household appliances and vehicles to industrial machinery. While there are temperature fuses that operate based on heat, this article focuses on current fuses, which are commonly referred to simply as “fuses.”
The Role of Fuses
Fuses are used to prevent electrical devices from entering dangerous conditions caused by overcurrent in a circuit.
To achieve this, the fuse element is made of a low-melting-point metal. When current flows through the metal, Joule heat is generated. If the current exceeds the fuse’s rated value, the temperature of the metal rises, causing it to melt and break the circuit.
Below is the process by which a fuse element melts due to electrical current.
Steady Current
Heat is evenly distributed across the fuse element.
Overload
As the current increases, heat begins to rise and spread from the center of the element.
Melting (Blowout)
When the current reaches the fuse’s melting point, the metal melts and breaks the circuit.
During this melting process, an arc is generated, which shares the load of the supply voltage. This causes a temporary drop in the circuit’s applied voltage, suppressing the increase of abnormal current.
The fuse element is made from an alloy composed of metals such as lead, tin, bismuth, cadmium, silver, and copper. By adjusting the composition, the melting point can be set within a range of 70 to 100°C.
Fuses operate by detecting abnormal temperature rises, and their melting characteristics vary depending on the structure of the fuse element, such as its heat generation capacity and thermal time constant.
Parts of a Fuse
The structure of a fuse is designed as a compact safety device used to protect electrical circuits. Its basic components are as follows:
① Fuse Element (Conductor Section)
This is the core part of the fuse; typically made of metals such as lead or copper. The metal wire generates heat and melts when the current exceeds a certain threshold, interrupting the flow of electricity.
② Body (Tubular or Flat Case)
The outer structure that protects the fuse element, made of heat-resistant materials such as hardened glass, ceramic, or plastic. This casing prevents sparks and heat from escaping during a blowout.
③ Terminals
These are the parts that connect the fuse to the electrical circuit, allowing it to be securely installed within the circuit.
④ Arc-Extinguishing Material
Some fuses are filled with materials to suppress arc discharge, enhancing safety during operation.
With this simple structure, fuses play a crucial role in detecting overcurrent and quickly interrupting circuits to ensure safety.
Glass Tubes vs. Ceramic Tubes: Key Differences
There are two main types of tube fuses based on the material of the tube: glass tube fuses and ceramic tube fuses.
Glass tube fuses are the most common type of tube fuse. The tube is made of transparent glass, allowing the fuse element inside to be visually inspected, making it easy to check for a blown fuse or other conditions from the outside.
Glass tubes have relatively low heat and voltage resistance, making them commonly used in low-power circuits and general household appliances.
In contrast, ceramic tubes offer high heat and voltage resistance, making them suitable for use in circuits with large currents or high voltages.
Glass tubes are well-suited for use in relatively light-load circuits, such as household appliances and small electronic devices.
On the other hand, ceramic tubes are commonly used in industrial equipment, applications involving high current and voltage, or in high-temperature environments.
In terms of cost, glass tubes are generally more affordable, while ceramic tubes are slightly more expensive.
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