The composition of the fuses

Ⅰ. Introduction of fuses

A fuse is a safety device used for circuit protection, it is mainly used to protect the circuit from overcurrent damage. When the current in the circuit exceeds the rated current capacity of the fuse, the fuse will blow, interrupting the circuit and preventing excessive current from flowing, thereby protecting the circuit and related equipment.

Fuses are also called current fuses, which are mainly used for overload protection. If the fuse is correctly placed in the circuit, the fuse will fuse itself to cut off the current when the current abnormally rises to a certain height and heat, thus protecting the safe operation of the circuit.

When a fault or abnormality occurs in a circuit, the current increases continuously, and the increased current may damage some important components in the circuit, burn the circuit or even cause a fire. If the fuse is correctly placed in the circuit, the fuse will fuse itself to cut off the current when the current abnormally rises to a certain height and heat, and play a role in protecting the safe operation of the circuit.

Ⅱ. Composition of the fuses

The fuse consists of three parts: the melt part, the bracket part, and the electrode part.

1. Melt part: it is the core of the fuse, and it plays the role of cutting off the current when it is blown. The melt of the same type and the same specification of the fuse should have the same material, the same geometric size, and the resistance value should be as small as possible and consistent. The most important thing is that the fusing characteristics should be consistent. Household fuses are often made of lead-antimony alloys.

2. Bracket part: The melt of the fuse is generally slender and soft. The function of the bracket is to fix the melt and make the three parts rigid and easy to install and use. It must have good mechanical strength, insulation, and heat resistance. In use, there should be no fracture, deformation, burning and short circuit.

3. Electrode part: There are usually two, it is an important part of the connection between the melt and the circuit, it must have good electrical conductivity, and should not produce obvious installation contact resistance.

Fuse elements are made of zinc, copper, silver, aluminum, or alloys of these or various other metals to provide stable and predictable characteristics. Ideally, a fuse will carry its rated current indefinitely and melt quickly with a small excess. The component must not be damaged by minor harmless current surges, and must not oxidize or change its behavior after years of use.

The fuse element can be shaped to increase the heating effect. In large fuses, the current can be divided among multiple metal bars. A dual-element fuse may contain a metal strip that melts immediately in a short circuit, and also contains a low-melting solder joint that responds to long-term overloads of low value compared to a short circuit. Fuse elements may be supported by steel or nichrome wire so no strain is placed on the element, but springs may be included to increase the speed at which fragments of the element separate.

Fuses device

The fuse device is a device used for circuit protection. Its function is to detect and protect the overcurrent situation in the circuit. When the current exceeds the rated current capacity of the fuse device, the fuse device will fuse quickly to interrupt the circuit and prevent excessive The current flows, thereby protecting the circuit and related equipment.

The fuse has a blown indicator device. Its function is to change the appearance of the fuse itself after it operates (fuse), which is easy to be found by maintenance personnel, such as: glowing, changing color, popping up solid indicators, etc.

Arc extinguishing device

An arc extinguishing device is a device used to extinguish an arc in a circuit, and it is used to eliminate or weaken the arc generated in the circuit. Arcing is an electrical spark that occurs when an electrical current is interrupted or a switch cuts, which can cause arc faults and equipment damage, as well as potentially fire and safety hazards.

The function of the arc extinguishing device is to eliminate the arc phenomenon by controlling the formation and dissipation of the arc. When the current in the circuit is interrupted or the switch is cut off, the arc extinguishing device will apply a certain amount of energy to the place where the arc is generated, so that the arc will lose its maintenance condition, so that the arc will be extinguished quickly.

The fuse used in power circuits and high-power equipment not only has three parts of the general fuse, but also has an arc extinguishing device, because the circuit protected by this type of fuse not only has a large working current, but also two parts of the fuse when the fuse is blown. The voltage at the terminal is also very high, and it often appears that the melt has melted (fuse) or even vaporized, but the current has not been cut off. arc phenomenon. This arc extinguishing device must have strong insulation and good thermal conductivity, and is negatively charged. Quartz sand is a commonly used arc extinguishing material.

The working principle of the arc extinguishing device can be to accelerate the movement of the arc, diffuse the arc energy, or control the movement and dissipation of the arc by applying a specific electromagnetic field.

Ⅲ. Function of the fuses

1. Equipment protection: The fuse plays a role in protecting the equipment in the circuit. Insert a fuse in the circuit, and when there is a problem with the device or the circuit, the fuse will disconnect to protect the device from damage.

2. Overload protection: When the current in the circuit exceeds the rated current capacity of the fuse, for example, due to circuit failure or equipment failure causing excessive current to flow, the fuse will immediately blow and interrupt the circuit to prevent excessive current from causing damage to the circuit and equipment. damage.

3. Safety guarantee: the use of fuses can prevent circuit damage, equipment damage, fire and other accidents caused by overcurrent, and ensure the safety of personnel and equipment.

4. Circuit protection: the fuse can prevent short-circuit faults in the circuit. When the circuit is short-circuited, the fuse will quickly melt and cut off the circuit to prevent excessive current at the short-circuit location, avoid damage to equipment and circuits, and avoid fires caused by large currents. and other security risks.

Ⅳ. Working principle of fuses

When the material and shape of the fuse are determined, its resistance R is relatively determined. The size of the current and resistance determines the speed of heat generation, and the structure of the fuse and its installation condition determine the speed of heat dissipation. If the speed of heat generation is lower than the speed of heat dissipation, the fuse will not blow. If the speed of heat generation is equal to the speed of heat dissipation, it will not fuse for a long time.

If the rate of heat generation is greater than the rate of heat dissipation, more and more heat will be generated. And because it has a certain specific heat and mass, the increase of its heat is manifested in the rise of temperature. When the temperature rises above the melting point of the fuse, the fuse will blow.

When the current in the circuit is below the rated current capacity of the fuse, the conductive material of the fuse element will conduct current normally. At this point, the fuse behaves as a low resistance wire and has no effect in the circuit.

When the current in the circuit exceeds the rated current capacity of the fuse, the fuse element will heat up due to the thermal effect of the excessive current. The conductive material of the fuse element heats up rapidly until it reaches its melting point.

When the temperature of the fuse element reaches the melting point, the fuse element melts rapidly, creating a break point. This interruption point causes the circuit to be interrupted, and current cannot continue to flow, thus cutting off the path for excessive current flow.

Ⅴ. History of Fuses

The earliest fuses date back to the early 19th century. At that time, people began to use simple metal wires or lead wires as fuses to protect circuits and equipment from excessive current damage. These early fuses were not as precise and reliable as modern fuses, but they were beginning to function as overload protection.

Fuses have been improved and standardized with the development of power systems and electronic equipment. In the late 19th and early 20th centuries, the design and manufacture of fuses became more precise and reliable. Some international standardization organizations have also begun to issue relevant standards, regulating the rated current capacity, rated voltage, size and other parameters of the fuse.

With the continuous advancement of electronic technology, fuses have been further improved and developed. Modern fuses typically consist of fuse elements made of conductive materials such as copper, lead, silver, etc., for greater accuracy and reliability. Modern fuses are widely used in various fields such as household appliances, industrial equipment, automotive electronic systems, and power systems, and play an important role in circuit protection.

With the application of digital technology, electronic fuses have gradually developed. Digital fuses utilize electronic components for overload protection, with faster response times and more precise protection characteristics.

Ⅵ. Classification of fuses

1. By volume

Power fuse: A device used for power system protection, also known as a high-voltage fuse or a high-voltage fuse. Due to the larger rated voltage and current, power fuses usually have larger volume and structure to meet the requirements of high-voltage power systems.

Machine tool fuse: It is a device used for machine tool circuit protection. It is mainly used to protect machine tools and related equipment from damage caused by overcurrent and short circuit faults. The rated voltage and current capacity of machine tool fuses are generally suitable for the requirements of machine tool circuits, and are generally lower than fuses for high-voltage power systems.

The rated current capacity of the machine tool fuse can be selected according to the power and electrical load of the machine tool. The selection of machine tool fuses needs to consider the power requirements and electrical load characteristics of the machine tool to ensure that the fuse can work reliably when the machine tool is running normally, and at the same time, it can quickly fuse and cut off the circuit when a fault occurs.

Electrical instrument fuse: It is a fuse used to protect electrical instrument circuits. It is mainly used to protect electrical instrument equipment from overcurrent and short-circuit faults. : The rated voltage and current capacity of electrical instrument fuses are usually suitable for the requirements of electrical instrument circuits, and are generally lower than those of high-voltage power system fuses. The rated current capacity of the electrical instrument fuse can be selected according to the power and electrical load of the instrument equipment. The selection of fuses for electrical instruments needs to consider the power requirements and electrical load characteristics of the instrumentation equipment to ensure that the fuse can work reliably when the instrumentation equipment is in normal operation, and at the same time, it can quickly fuse and cut off the circuit when a fault occurs.

Automobile fuse: It is a device used for automobile circuit protection. It is mainly used to protect automobile circuits from overcurrent and short circuit faults. Automobile fuses are mainly used to protect automobile circuits, prevent faults caused by circuit overload and short circuit, and ensure the safe operation of the automobile's electrical system. Automobile fuses are usually fire-proof and explosion-proof, which can effectively prevent fires when the fuse blows.

2. According to the form of protection

Current-limiting fuse: is a special type of fuse that has the ability to limit current and is used to protect circuits and equipment from overcurrent damage. The current-limiting fuse is designed with special current limiting characteristics. When the current in the circuit exceeds the rated current capacity of the fuse, it will respond quickly and limit the current within a certain range to prevent excessive current from flowing. Current-limiting fuses are widely used where highly reliable current protection is required, such as are commonly found in power systems, industrial equipment, and high-power electronic equipment. The use of current-limiting fuses can prevent circuit damage, equipment damage, fire and other accidents caused by circuit overload and short-circuit faults.

Thermal fuse: Commonly used in today's electric heating devices, it will fuse when the temperature exceeds the safe temperature. Devices with thermal fuses, such as electric cookers, electric heaters, coffee machines, hair dryers, etc. Although there is an item of allowable current in the specifications of the thermal fuse, the thermal fuse does not have the same current protection function as the current fuse. Due to the larger rated voltage and current, power fuses usually have larger volume and structure to meet the requirements of high-voltage power systems.

3. Divided by shape

Pointed Tubular Fuses: Pointed Tubular Fuses are usually a long, thin tube with sharp, blade-like ends. This form factor allows easy insertion or extraction during installation and replacement. The pointed tubular fuse can respond quickly when the circuit is overloaded, quickly blown, cut off the circuit, prevent excessive current from flowing, and play a role of rapid protection.

Flat Tubular Fuses: Flat Tubular Fuses usually have a rectangular or rectangular plan shape with flat ends, rather than the sharp blades of pointed Tubular Fuses. This form factor allows easy insertion or extraction during installation and replacement. The flat-head tubular fuse can respond quickly when the circuit is overloaded, quickly blown, cut off the circuit, prevent excessive current from flowing, and play a role of rapid protection. Flat-head tubular fuses are usually fire-proof and explosion-proof, and can effectively prevent fires when the fuse blows.

Spiral Fuse: A spiral fuse is a cylindrical, usually helical coil of conductive material that contains a length of the fuse element. Spiral fuses are usually cylindrical in shape, with different diameters and lengths to suit different rated currents and application scenarios. When the circuit is overloaded, the spiral fuse can respond quickly, fuse quickly, cut off the circuit, prevent excessive current from flowing, and play a role of rapid protection.

Guillotine fuse: Guillotine fuse looks like a guillotine, with parallel metal blades at both ends and a fuse element connected in the middle. This design allows the guillotine fuse to quickly cut off the circuit when it blows.

SMD fuse: It is a special type of fuse, also known as SMD fuse. SMD fuses are usually rectangular or square in shape and are suitable for surface mount technology. They do not have the wires and fuses of traditional fuses, but use miniature packaging and thin-film technology, making them suitable for the design of high-density integrated circuit boards. Chip fuses are soldered directly to the surface of the printed circuit board (PCB) through surface mount technology, making assembly more efficient and automated.

Flat fuse: The shape of the flat fuse is rectangular or rectangular, with flat ends and no sharp blades, which are easy to insert and pull out. Flat fuses are a common and practical type of fuse that are easy to install and replace, and provide quick and reliable protection against circuit overloads.

4. According to the breaking capacity

Low breaking capacity fuse: refers to a type of fuse with a small rated current and relatively low breaking capacity. Breaking capacity refers to the ability of a fuse to safely cut off a circuit in the event of an overload or short circuit to prevent hazards such as arcing and fire. The rated current of the low breaking capacity fuse is relatively small, usually in the range of several hundred mA or lower, and is used for the protection of small current circuits. Due to the small rated current, the breaking capacity of the low breaking capacity fuse is usually lower, which is suitable for circuit protection of smaller power. Although the capacity of the low breaking capacity fuse is limited, it can effectively protect smaller power circuits from overcurrent and short circuit damage when used within the correct rated current range.

High breaking capacity fuse: The rated current of the high breaking capacity fuse is relatively large, usually in the range of tens of A or higher, and is used for the protection of high-power circuits. High breaking capacity fuses can effectively protect high-power circuits from damage caused by overcurrent and short-circuit faults, and ensure the safe operation of equipment and systems.

Ⅶ. Common fuse shapes

1.Barrel Fuse: This type of fuse is cylindrical in shape and is usually used in high current or high voltage applications, as well as in automotive circuits.

2. Glass Tube Fuse: This is a common type of fuse, shaped like a slender glass tube. Typically, inside is a thin wire (usually copper or silver) that connects to metal terminals at both ends.

3.Wire Fuse: This type of fuse has a thin wire or filament shape and is used for lower current applications. Usually used for the protection of electronic components.

4.Cylindrical Fuse: This type of fuse has a cylindrical shape with metal terminals at both ends, and is often used in high-current applications. There are also some special types of cylindrical fuses, such as lead-sealed fuses, which are encapsulated in a metal case.

5. Rectangular or Blade Fuse: This type of fuse has a rectangular or rectangular shape and is sometimes called a blade fuse. They are widely used on surface mount electronics for ease of automated assembly.

6. Ceramic tubular: There are several different shapes and sizes to avoid glass bursting.

Ⅷ. Factors related to the life and reliability of the fuse

1. Rated current and voltage: When using a fuse, it must be ensured that its rated current and voltage match the actual circuit requirements. Over- or under-ratings can cause the fuse to trip under inappropriate conditions or fail to trip.

2. Overvoltage protection: In some cases, an overvoltage situation may occur in the circuit, and the excessive voltage may damage the fuse. Therefore, the rated voltage of the fuse should match or be slightly higher than the maximum operating voltage of the circuit.

3. Thermal stability: The material and design of the fuse should have good thermal stability in order to maintain stability at rated current and trigger quickly when overloaded.

4. Overload and short circuit events: Fuses are designed to trigger and cut off the current when an overload or short circuit occurs in the circuit, thereby protecting the circuit and equipment. Frequent overload or short circuit events can shorten the life of the fuse.

Ⅸ.What is fuse characteristics?

Fuses could be used in place of circuits. It must have a low melting point and high specific resistance. It must be economical as it can be made from silver metal, but silver metal is too expensive.

X.Which property of wire is used in fuse?

Low melting point is the property which is useful in making an electric fuse. Wire melts and breaks the circuit If large current is passed through the wire.