What action is used in fuses. Types of fuses

What are fuses and what are they for?

Fuses, along with circuit breakers, are used to protect elements and devices of electrical installations from damage that may occur during abnormal conditions that threaten the integrity of individual elements or the entire installation. Typically, fuses are used to protect cables, wires and electrical devices of high and low current and more or less significant overloads.

The comparative cheapness and simplicity of the design of fuses have led to their widespread use in all cases where they are suitable for protecting electrical installations. However, being simple in design, fuses have a number of disadvantages that determine their use in electrical installations with simple switching circuits and to protect elements of installations that do not have high requirements for overload protection.

The main disadvantages of fuses are:

the difficulty, and in some cases the impossibility, of obtaining their selective action both during short circuits in the network and during overloads;

the low suitability of most fuses for protection against small overloads;

the need for a special switching device (switch, disconnector), since the fuse, unlike circuit breakers, can only perform automatic shutdown in emergency modes, being an uncontrolled device in normal modes;

the need to replace one of the parts of the fuse (fuse link) after it has tripped.

Currently, the development of fuses with more advanced characteristics is underway, allowing for reliable protection against overloads and having a higher selective effect.

Fuses are usually classified according to the following criteria:

design;

rated voltage;

rated current.

Currently, a large number of different types of fuses are manufactured. See more about this here:

Characteristics

The dependence of the total combustion time of the fuse-link and the extinguishing of the resulting arc on the multiplicity of the current fusing the link in relation to the rated current of the fuse insert is called the fuse characteristic, or, in other words, the ampersecond (protective) characteristic.

Protective characteristic

The characteristics of the fuse are determined by:

the ability to protect the installation element from overloads;

selectivity of the action of the fuse in conjunction with the action of other fuses and relay protection of the circuit in which the fuse is installed.

By selecting the appropriate amperesecond characteristics of the fuse links of sequentially connected fuses of adjacent sections of the network, we achieve selectivity of their action, i.e., such an action in which the insert of a fuse lower in the direction of supply blows out before the insert of a higher-level fuse has time to burn out.

When selecting fuse links according to the conditions of selectivity of protection, the condition must also be met that the rated current of the fuse link does not exceed the value determined by the rules for the protected element of the installation.

An important characteristic of a fuse is its breaking capacity, which determines the maximum value of the short circuit current cut off by the fuse. The breaking capacity of the fuse depends on the speed of extinguishing the arc when the fuse link burns out, and, other things being equal, the lower the ampersecond characteristic of the fuse link, the greater it is.

Fuse arrangement

As mentioned above, the main purpose of a fuse is to protect elements of electrical installations from overloads and short circuits. A fuse connected in series with the protected element blows when the current of the protected circuit exceeds the rated current of the fuse link by a certain amount. In this case, the fuse automatically turns off the damaged section of the network. The fuse does not respond to any other deviations from the normal operation of the network. To restore power to a network section when a fuse link burns out, it is necessary to replace the burnt-out fuse link with a new one.

The main parts of any fuse are:

fusible link;

an element used to place (attach) a fuse-link and create conditions for extinguishing the arc when the fuse-link burns out;

fuse base in the form of a stand or socket, depending on the type of fuse, with a clamp for connection to the electric current circuit.

The base of the fuse and the element used to accommodate the fuse link are equipped with corresponding contact devices. With the help of contact devices, the element is fixed to the base of the fuse, and the reliable inclusion of the fuse-link in the protecting current circuit is ensured.

Some fuses are equipped with additional devices: clamps to prevent the fuses from falling out during vibration, handles for convenient and safe removal of the removable fuse element from the switchgear, etc.

Installation and operation of fuses

Tubular fuses must be installed on vertical planes with contact posts installed strictly vertically. It is strictly prohibited to install non-factory fuse links or inserts not intended for this type of cartridge, in order to avoid tube rupture and overlap when the fuse trips. The rated current of the fuse link must correspond to the data of the protected element of the installation.

During operation, you need to monitor the condition of fuses and distribution devices, avoiding contamination and dust, in order to avoid overlap between fuses of equal polarity. It is necessary to periodically clean the contact parts of the fuses from oxides. All operations to remove cartridges from contact posts must be carried out with specially designed devices (pliers, handles) with the voltage removed.

It is recommended to install fuses on vertical planes, but they can be installed on inclined and horizontal planes. To prevent overheating of the fuse terminals, it is necessary to carefully connect the supply wires using busbars or conductors of the proper cross-section. During operation, it is necessary to constantly monitor the correct tightening of the fuse links, turning the fuse head if necessary. It is recommended to lubricate the contact parts of the fuses with clean technical petroleum jelly.

Modern electrical networks and devices are very complex and require reliable protection against possible overloads and short circuits. The main protective role in such cases is played by various safety devices. Among the variety of these devices, the most common are fuses, which have a high degree of reliability, ease of operation and relatively low cost.

Despite the widespread use of automatic protective devices, fuse links remain relevant in protecting electronic equipment, automotive electrical networks, industrial electrical installations and power supply systems. They are still used in the distribution boards of many residential buildings due to their reliable operation, small size, stable performance and quick replacement.

What are fuses used for?

If two wires connected to a current source are connected, the well-known short circuit effect will occur. The reason may be damaged insulation, incorrect connection of consumers, etc. With a relatively low resistance of the wires, at this moment a very high current will flow through them. As a result of overheating of the wires, the insulation catches fire, which can lead to a fire.

It is quite possible to avoid negative consequences by including fuses, also known as plugs. If the current exceeds the permissible value, the wire inside the fuse becomes very hot and quickly melts, breaking the electrical circuit at this point.

The design of fuses can be tubular or plug. Tubular elements are manufactured in a closed fiber casing with gas generation properties. If the temperature rises, high pressure is created inside the tube, causing the circuit to break. Plug fuses have a standard design, equipped with a wire that melts under the influence of high electric current.

There is another type of so-called self-healing fuses, made of polymer materials that change their structure at different temperatures. Significant heating leads to a sharp change in resistance towards an increase, as a result of which the circuit breaks. Further cooling causes a decrease in resistance, so the circuit closes again. These fuses are mainly used in complex digital devices. They are not used in conventional power networks due to their high cost.

Sometimes some craftsmen try to replace a blown fuse, using instead so-called bugs, which are a piece of thick wire or thin wires twisted into a common bundle. It is strictly forbidden to use such homemade devices, since the current during a short circuit will be unacceptably high. Extreme heating of the wiring will cause damage, ignition and fire.

Fuse device

The composition includes a housing or cartridge with electrical insulating properties, and the fuse link itself. Its ends are connected to terminals that connect the fuse in series with the electrical circuit, together with the protected device or electrical line. The material of the fuse link is selected so that it can melt before the temperature indicator of the wires reaches a dangerous level, or the consumer fails as a result of overload.

Based on their design features, fuses can be cartridge, plate, plug and tube. The calculated current strength that the fuse link can withstand is indicated on the device body.

Low-voltage fuses have a fairly simple design. Under the influence of high current, the fuse-link or conductive element is subjected to intense heating, after which, upon reaching a certain temperature, it melts in the arc-extinguishing medium and evaporates, breaking the protected circuit. This is how a fuse works in an electrical circuit.

To prevent hot gases and liquid metal from entering the environment, a ceramic insulator is used, also known as the device body, which is resistant to high temperatures and significant internal pressure. The protective covers located at the edges of the fuse are equipped with special strips for unified handles that grip fuse-links when replacing unusable elements. With the help of protective covers and a ceramic housing, an explosion-proof shell is created that limits the switching electric arc.

Sand filling the internal space limits the current. The material is selected with certain crystal sizes, after which it is compacted properly. As a rule, fuses are filled with quartz crystalline sand, which has high chemical and mineralogical purity. The connection of the fuse-link with the base-holder is carried out mechanically, using contact knives. They are made from copper or copper alloys coated with tin or silver.

Fuse characteristics

The main characteristic is the direct dependence of the melting time on the current strength. Therefore, the time during which the fuse link blows out corresponds to a certain current. This parameter is better known as the time-current characteristic.

In addition to the time indicator, there are other characteristics that are used to determine the types of fuses. Among them, first of all, it should be noted. This is the most permissible load current under the conditions of heating the fuse body for a long time. When choosing a device based on this indicator, the load of the electrical circuit must be taken into account, as well as the operating conditions of the fuse.

In some cases, the current rating may be higher than the current in the electrical circuit itself. For example, in electric motor starters to avoid the fuse blowing during starting. It should be taken into account that the rated current of the fuse must correspond to the rated current of the element being replaced.

In turn, the rated current of the element being replaced represents the maximum permissible load current for a long time when this element is installed in the holder or contacts. In addition, there are base and fuse holder current ratings that must be taken into account when selecting a protective device. In addition, an indicator such as rated voltage is used. This parameter represents the interpole voltage, which coincides with the rated phase-to-phase voltage of the protected electrical networks.

In order for fuses to provide reliable protection, the value of this value must be greater than or equal to the voltage of the protected object. For example, a fuse rated 400 volts can be used to protect 220 volt circuits, but not vice versa. Thus, this value characterizes the ability of the fuse to promptly break the electrical circuit and extinguish the arc.

Therefore, when choosing a fuse as a protective device, it is imperative to take into account the parameters that make it possible to ensure reliable protection of the object.

Types of fuses

For all devices of this type, there is a general classification according to their basic properties.

Fuse links can close in different ways, and therefore the external effects that occur when the current is turned off are also different. Such fuses are divided into the following types:

• An open fuse-link in which there are no devices to limit the volume of the arc, the emission of molten metal particles and flame.
• A semi-closed cartridge with a shell open on one or both sides. It creates a certain danger for people nearby.
• Closed cartridge. It is the most reliable because it does not have all of the above disadvantages. Almost all modern fuses are produced with a closed cartridge.

Extinguishing the arc can be done in different ways. Depending on this, fuses are available with or without filler. In the first case, powdery, fibrous or granular components are used, and in the second, due to the movement of gases or high pressure in the cartridge. The designs of the cartridges themselves are divided into collapsible and non-collapsible. The first option involves replacing the melted insert, and in the second case the entire element will have to be replaced. In some cases, non-separable cartridges can be reloaded in special workshops.

Fuses may or may not be replaced while energized. In the first case, replacement can be done directly by hand, without touching live parts. In the second case, the device must be disconnected from the voltage.

Fuse markings

Each fuse in the diagram is indicated by a specific symbol. The standard marking consists of two letter characters. The first letters determine the protective interval: a - partial (protection against short circuits only) and g - complete (protection against short circuits and overloads is provided).

The second letter indicates the types of protected devices:

• G - protects any equipment.
• F - only low current circuits are protected.
• Tr - transformer protection.
• M - electric motors and disconnecting devices.

More detailed information about fuse markings can be obtained from reference books intended for electrical engineers.

Any electrical circuit consists of individual elements. Each of them is characterized by certain current values ​​at which this element is operational. Increasing the current above these values ​​may cause damage to the element. This occurs due to an unacceptably high temperature or due to a fairly rapid change in the structure of this element due to the influence of current. In such situations, fuses of various designs help avoid damage to electrical circuit elements.

Their classification is based on the way these fuses break the electrical circuit, and therefore we can list those that are most widely used as the following types of fuses:

• fusible,
• electromechanical,
• electronic,
• self-healing.

The method of breaking an electrical circuit covers the entire set of processes that occur in the fuse when it is triggered.

• Fuses break the electrical circuit as a result of the melting of the fuse link.
• Electromechanical fuses contain contacts that are switched off by a deformable bimetallic element.
• Electronic fuses contain an electronic key, which is controlled by a special electronic circuit.
• Self-resetting fuses are made using special materials. Their properties change when current flows, but are restored after the current in the electrical circuit decreases or disappears. Accordingly, the resistance first increases and then decreases again.

Fusible

The cheapest and most reliable are fuses. A fuse link, which melts or even evaporates after increasing the current above the set value, is guaranteed to create a break in the electrical circuit. The effectiveness of this method of protection is determined mainly by the rate of destruction of the fuse-link. For this purpose, it is made of special metals and alloys. These are mainly metals such as zinc, copper, iron and lead. Since the fuse link is essentially a conductor, it behaves like a conductor, which is characterized by the graphs shown below.

Therefore, for proper operation of the fuse, the heat that is released in the fuse-link at the rated load current should not lead to its overheating and destruction. It dissipates into the environment through the elements of the fuse body, heating the insert, but without destructive consequences for it.

But if the current increases, the heat balance will be disrupted and the temperature of the insert will begin to increase.

In this case, an avalanche-like increase in temperature will occur due to an increase in the active resistance of the fuse-link. Depending on the rate of temperature rise, the insert either melts or evaporates. Evaporation is facilitated by a voltaic arc, which can occur in a fuse at significant values ​​of voltage and current. The arc temporarily replaces the destroyed fuse-link, maintaining current in the electrical circuit. Therefore, its existence also determines the timing characteristics of fuse-link disconnection.

• The time-current characteristic is the main parameter of a fuse-link, by which it is selected for a particular electrical circuit.

In emergency mode, it is important to break the electrical circuit as quickly as possible. For this purpose, special methods are used for fuse links, such as:

• local reduction in its diameter;
• "metallurgical effect".

In principle, these are similar methods that allow, one way or another, to cause local, faster heating of the insert. A variable cross-section with a smaller diameter heats up faster than with a larger cross-section. To further speed up the destruction of the fuse-link, it is made composite of a pack of identical conductors. As soon as one of these conductors burns out, the total cross-section will decrease and the next conductor will burn out, and so on until the entire pack of conductors is completely destroyed.

The metallurgical effect is used in thin inserts. It is based on obtaining a local melt with a higher resistance and dissolving the base material of the low-resistance insert in it. As a result, local resistance increases and the insert melts more quickly. The melt is obtained from drops of tin or lead, which are applied to a copper core. Such methods are used for low-power fuses for currents up to several units of ampere. They are mainly used for various household electrical appliances and devices.

The shape, dimensions and material of the housing may vary depending on the fuse model. The glass case is convenient because it allows you to see the state of the fusible insert. But the ceramic case is cheaper and stronger. Other designs are adapted for specific tasks. Some of them are shown in the image below.

Conventional electrical plugs are based on tubular ceramic bodies. The plug itself is a body that is specially made to fit the cartridge for convenient use of the fuse. Some designs of plugs and ceramic fuses are equipped with a mechanical indicator of the status of the fuse link. When it burns out, a semaphore-type device is triggered.

When the current increases beyond 5 - 10 A, it becomes necessary to extinguish the voltage arc inside the fuse body. To do this, the internal space around the fusible insert is filled with quartz sand. The arc quickly heats the sand until gases are released, which prevent further development of the voltaic arc.

Despite certain inconveniences caused by the need for a supply of fuses for replacement, as well as slow and insufficiently accurate operation for some electrical circuits, this type of fuses is the most reliable of all. The higher the rate of increase in current through it, the greater the reliability of operation.

Electromechanical

Fuses of electromechanical design are fundamentally different from fuses. They have mechanical contacts and mechanical elements to control them. Since the reliability of any device decreases as it becomes more complex, for these fuses, at least theoretically, there is a possibility of such a malfunction in which the set tripping current will not be turned off. Repeated operation is a significant advantage of these devices over fuses. Disadvantages can be identified as:

• the appearance of an arc when turned off and the gradual destruction of contacts due to its influence. It is possible that the contacts may be welded together.
• Mechanical contact drive, which is expensive to fully automate. For this reason, re-enabling has to be done manually;
• insufficiently fast response, which cannot ensure the safety of some “perishable” electricity consumers.

An electromechanical fuse is often referred to as a “circuit breaker” and is connected to the electrical circuit either by a base or by wire terminals stripped of insulation.

Electronic

In these devices, mechanics are completely replaced by electronics. They have only one drawback with its several manifestations:

• physical properties of semiconductors.

This disadvantage manifests itself:

• in irreversible internal damage to the electronic key from abnormal physical influences (excess voltage, current, temperature, radiation);
• false activation or breakdown of the electronic key control circuit due to abnormal physical influences (excess of temperature, radiation, electromagnetic radiation).

Self-healing

A bar is made of a special polymer material and equipped with electrodes for connection to an electrical circuit. This is the design of this type of fuse. The resistance of a material in a given temperature range is small, but increases sharply starting from a certain temperature. As it cools, the resistance decreases again. Flaws:

• dependence of resistance on ambient temperature;
• long recovery after triggering;
• breakdown by excess voltage and failure for this reason.

Choosing the right fuse provides significant cost savings. Expensive equipment, timely switched off by a fuse in the event of an accident in the electrical circuit, remains operational.

A fuse is an electrical element that performs a protective function. Unlike a circuit breaker, after each operation it needs to replace the circuit-breaking part. The fuse link, which burns out when the permissible rated current is exceeded, must be selected taking into account the load on the network.

Operating principle and purpose of fuses

Inside the fuse insert there is a conductor made of pure metal (copper, zinc, etc.) or alloy (steel). Circuit protection is based on the physical property of metals to heat up when current passes. Many alloys also have a positive coefficient of thermal resistance. Its effect is as follows:

• when the current is below the rated value provided for the conductor, the metal heats up evenly, managing to dissipate heat, and does not overheat;
• too much current leads to strong heating, and an increase in the temperature of the metal causes an increase in its resistance;
• Due to the increased resistance, the conductor heats up even more intensely, and when the melting point is exceeded, it is destroyed.

The fusing of the insert placed in the electrical fuse is based on this property. Depending on the application, the shape and cross-section of the conductor can be different: from thin wire in household and automotive appliances to thick plates designed for a current of several thousand amperes (A).

The compact part protects the electrical circuit from overload and short circuit. If the permissible current for the network (i.e., rated) current is exceeded, the insert is destroyed and the circuit breaks. Its operation can be restored only after replacing the element. When there is a defect in the connected equipment, the fuses will blow immediately after the faulty device is turned on, allowing the cause to be determined. If a short circuit occurs in the network, the protective device operates in the same way.

Conventional graphic symbol on the diagram

According to the Unified System of Design Documentation of Russia, on graphical circuit diagrams, fuses are designated by a rectangle with a straight line running inside it. Its ends are connected to 2 parts of the circuit before and after the protective device.

In the documentation for imported devices you can find other designations:

• rectangle with separated parts at the ends (IEC standard);
• wavy line (IEEE/ANSI).

Types and types of fuses

For use in electrical circuits, different types and varieties of PP are used. Products manufactured in Russia differ in type of design:

The concept of fullness is associated with the presence inside certain types of inserts of a substance that extinguishes the electric arc that occurs at the moment the conductor burns out. The circuit will be opened only after it disappears. Therefore, flasks filled with PP contain quartz sand. Unfilled ones can release gases that extinguish the arc. This occurs when the material of the insert body is heated.

In addition to types, there are different types of PP:

1. Low-current ones are used in low-power household appliances with a current consumption of up to 6 A. These are cylindrical inserts with contacts at the ends.
2. Fork-mounted PCBs are often installed in cars. The name is due to its appearance: the contacts are on one side of the case and are inserted into the connectors, like a plug into a socket.
3. Plug plugs are common electrical plugs for the meter in single-phase networks. The rated current of such inserts is 63 A; they are designed for simultaneous activation of several household appliances. The blown insert in such a fuse is located inside a ceramic housing with a cartridge; 1 contact remains outside, and the other is connected to the contacts of the plug. If the load is exceeded, the part burns out, completely cutting off power to the apartment. The power supply can be restored by replacing the insert with a new one.
4. The structure of the tubular PP resembles an insert for plugs, but its fastening is made between 2 contacts. The type of such fuse is unfilled, and the body is made of fiber, which releases gas when heated strongly.
5. Blade fuses are designed for a current value of 100-1250 A and are used in networks where a high load is needed (for example, when connecting a device with a powerful motor).
6. Quartz, filled with quartz sand, are used in networks with voltages up to 36 kV.
7. Gas-generating, collapsible and non-dismountable. When varieties of PSN and PVT are burned, a powerful release of gas occurs, accompanied by popping. PP is used for networks with voltage 35-110 kV. The rated current of such a PP is up to 100A.

Depending on the total load on the network, different types of PP are installed - more powerful ones are installed in special transformer booths; they can withstand the current that meets the needs of a residential area or enterprise. Low-power ones are installed in meters: they protect individual apartments. Old household appliances can also have a PP (low-current) installed, but modern appliances rarely contain these elements.

Selecting a fuse link

The selection of fuses is made taking into account their ratings, time-current characteristics and the total load on the network (the total power of all operating elements). The rated current of the PP is the one that the fuse link can withstand before destruction. This value is indicated on its body (for example, marking 63 A for cork household fuses).

Time-current characteristics are calculated using special graphs. They must be taken into account only when connecting an electric motor to the network, the starting current of which exceeds the operating voltage several times. When using several such devices (in an enterprise), the starting torque of the most powerful engine is calculated.

The total (maximum) load power of the network is the sum of all operating currents of the devices (indicated in the instructions and on the case). If an electric motor is connected to the network, then its starting torque is also taken into account, divided by the coefficient k = 2.5 (for easy starting and squirrel-cage rotors) or 2-1.6 (for hard-starting or phase-wound rotors).

In order not to waste time on calculations, select the rated current of the fuse link according to the table.

W	10	50	100	150	250	500	800	1000	1200	1600	2000	2500	3000	4000	6000	8000	10000
A	0,1	0,25	0,5	1	2	3	4	5	6	8	10	12	15	20	30	40	50

The first line (W) indicates the power of the device indicated on its body, and the second (A) indicates the fuse rating. For a residential network, you will have to add up the W values ​​of all home appliances and find the appropriate number in the table.

Calculation of fuse wire diameter

Complex calculations are made in order to temporarily repair a burnt insert if it is not possible to replace it. In order for the network to be protected from overload, the thickness of the wire used to install the “bug” must correspond to the rating of the destroyed insert. For the network of a city apartment, where a 63 A PP is installed, you can use copper wire with a diameter of 0.9 mm.

If repair of another protective device is required, then you need to determine the rating of the PP (indicated on the housing), and then determine the compliance of the existing copper wire:

• measure its diameter;
• cube this number and take the square root of the value;
• multiply the resulting figure by 80.

The result should be approximately equal to the PP rating indicated on the case.

During repairs, the selected wire is wound around the contacts of the burnt insert, connecting them. The bug is inserted into the socket on the fuse body.

If the wire melts again, it means that the fault is in the protected device or in the apartment’s network, and they must be repaired. You cannot use thicker wire, as this may cause a fire.

Functionality check

Modern car fuses sometimes have a built-in blown indicator. He tells the owner that the part needs to be replaced. In low-current PCBs, the wire is visible through the transparent body. But part of the software is opaque and has no indicators.

If it is impossible to visually determine a conductor break inside the PCB, then its performance can be determined with a multimeter. Before checking the fuse with a tester, you need to select the minimum resistance value (Ohm). Apply the tester probes to the contacts of the PP and determine the readings of the device:

• when the resistance value is zero or close to 0, a conclusion is drawn about the operability of the insert;
• if the tester shows 1 or an infinity sign, then the PP has burned out.

If the tester has a sound device, you can simply ring the fuse by applying probes to the contacts. The squeak of the tester indicates the serviceability of the element.

Modern electrical networks and devices are complex and require protection from overloads and short circuits, which can occur for a variety of reasons. In order to provide protection, various types of fuses and additional devices are used.

The modern market offers a large selection of different equipment, but the consumer prefers to use fuses. This is due to the fact that the device has a high degree of reliability and is easy to use. In addition, the affordable price pleases every consumer. Of course, first you need to find out.

Even though circuit breakers are widely used today, fuses still attract attention and remain relevant. The device is often used for protection of automobile electrical network, energy saving systems, electrical equipment, industrial electrical installations.

You can still find a similar device in many residential buildings. Interest will remain primarily due to reliable operation; the compactness of the product and stable characteristics also play an important role. If necessary, a replacement can be made in the shortest possible time. And yet, how does a fuse work and what is it for?

What are fuses used for?

The purpose of fuses is to protect elements and additional devices of electrical installations; circuit breakers are used for the same purposes. When electrical equipment operates abnormally, damage to individual components of the equipment or the entire system is often observed. A fuse is often used to protect electrical cables and wiring in order to avoid overloads and short circuits.

Operating principle of a fuse lies in the fact that it burns out before other elements of the system are damaged due to overloads. And this is undoubtedly an advantage, since it is much easier to replace a small element than to replace electrical wiring, microcircuits and additional devices. It must be said that not a single element is immune from overloads, and as a result, burnout.

The device is called fusible because it has a fusible element at its base - a special insert. It consists of an alloy with a low ignition temperature, and with a slight short circuit the heat is enough to melt the element. Thus, the circuit is open and nothing else threatens the integrity of the entire system.

Burnout can occur for a variety of reasons; it can be simply a short circuit, overload, or power surges, which is observed quite often.

In addition to the fact that this element protects the system from damage, it also protects against fire and fire. The fuse blows directly in the housing, while the electrical wiring may come into contact with combustible and flammable elements.

Some craftsmen make a bug, most often it is just a piece of wire that is used as a fuse. This is done because there is no fuse at hand that will meet all the requirements, and the protection must be bypassed in some way. But experts do not recommend this method, because such a bug may not burn out at all, and this will lead to a breakdown of the system and can be quite serious, or even a fire will occur.

Operating principle of fuses

Before purchasing, you need to learn in more detail how a fuse works. The great scientists Lenz and Joule established the laws of mutual relationships between the amount of current passing in a conductor and the release of heat. The dependence of circuit resistance over a certain period of time has helped to create the most simple, but incredibly effective methods of protection. The principle of this fuse is the thermal effect of current on the metal of the electrical wire. A rather thin metal insert carries the full eclectic current of the entire circuit.

During normal operation special insert successfully copes with its purpose, but if the norm is exceeded, the wire burns out, thereby breaking the circuit and removing the voltage from the consumer. By replacing a burnt-out element, you can restore the functionality of the entire system with minimal expenditure of both money and time.

The product can be seen on the design of radio or television equipment, where the housing is often glass and transparent.

There are special metal pads at the ends of the product; they, in turn, create contact when installed in the socket. A similar principle of operation is observed in electrical plugs with fusible inserts. Many years of practice show that this method is indeed incredibly effective and efficient.

How does a fuse work?

As is known, according to operating principle of fuses divided into automatic and fusible. The last option is ordinary traffic jams, and they are found quite often in everyday life. This is the most effective method of protection and there is no reason to install other equipment. They are screwed in directly next to the meter; the peculiarity of the product is that the base is the same as on a regular light bulb.

After the meter, the electric current spreads throughout the apartment. But it is worth knowing that not only the main input, but also each individual circuit should be protected from short circuits. If we are talking about old buildings, then plugs with thin conductive inserts are often used. And if there are no differences, and everything works normally, then this insert works successfully and performs its functions.

If the value exceeds the nominal value, then the insert simply burns out, thereby breaking the circuit. In order to restore normal operation, you just need to replace the burnt out element. To do this, you do not need to contact a specialist; even a person without special skills can make a replacement.

As for automation, they are made in a similar form. But the difference is that if power surges are observed, the plugs are turned off automatically, and to restore functionality you just need to press a button.

The automatic fuse of the PAR type is made by analogy with classic plugs, and is screwed into the cartridge instead of the fusible model. The most popular model of the PAR fuse, in the active state, closes the circuit with a central contact and a threaded sleeve via an electrical wire.

The wiring is wound around the electromagnet coil and connected to a bimetallic plate. If there is an overload, and as a result an increase in temperature, the plate bends and the wire is released, thereby shutting down. The machine button rises up, and this indicates that the mechanism has worked and fulfilled its protective function.

Fuse arrangement

The product contains a cartridge or housing, which necessarily has electrical insulating characteristics. And additionally present fuse link. The ends of the last element are connected to the terminals, and they, in turn, are responsible for sequentially connecting the fuse to the electrical circuit.

Based on the design features, fuses divided into tube, cartridge, cork, plastic. On the device body there is a calculated current strength that the product can withstand.

The design is equipped with a ceramic insulator, sometimes glass is used as a material; this element prevents gas and liquid metal from entering the environment. The housing is resistant to high temperatures and high pressure. Replacement of faulty fuse links is carried out very quickly, this is provided for by the design feature.

Sometimes the fuse is filled with quartz sand, which is designed to extinguish the arc in a short time. When the fuse-link burns out, an additional discharge occurs between the conductors. This in turn ionizes the air, which supports the arc. Quartz sand prevents fire.