The disposable component protects the power source from excessive load and is the weakest link in the electrical circuit. Fuses are included in almost all electrical systems. This device consists of a piece of wire, the cross-section of which is designed to carry a certain amount of current. When excessive load occurs in the circuit, the fuse element melts and breaks the circuit.

The main properties of a fuse are: rated voltage, rated current, maximum permissible current.

Some people believe that the quality of a fuse depends on the thickness of the wire in it. But it is not so. An unqualified calculation of the thickness of the fuse link can easily cause a fire, since in addition to the fuse itself, the wires that make up the circuit also heat up. If you install a fuse with a wire that is too thin, it will not ensure normal operation and will quickly break the circuit.

Operating principle

Fuses are included in the gap of an electrical circuit in such a way that the total load current of this circuit passes through them. Until the upper limit of the current is exceeded, the wire element is warm or cold. But, when a significant load appears in the circuit or a short circuit occurs, the current increases significantly, melts the fuse wire element, which leads to an automatic break in the circuit.

Fuses operate in 2 different modes:

• Normal mode , when the device is heated in a steady-state process in which the entire device is heated to operating temperature and releases heat to the outside. Each fuse indicates the highest current value at which the wire element melts. The insert body may contain fusible elements designed for different current strengths.
• Overload and short circuit mode . The device is designed in such a way that when the current increases to the upper permissible limit, the fusible element burns out very quickly. To achieve this property, the fuse element in some places is made with a smaller cross-section. They generate more heat than other places. During a short circuit, all narrow sections of the fusible element melt and open the circuit. At this time, an electric arc is formed around the melting point, which goes out in the fuse housing.

Marking

The designation of fuses is represented by two letters. Let's take a closer look at the marking of fuses.

The first letter determines the protection interval:

• a— partial interval (short circuit (short circuit) protection).
• g— full interval (protection against short circuit and overload).

The second letter determines the type of protected device:

• G— universal type for protecting various equipment.
• L— protection of wires and switchgears.
• B— protection of mining equipment.
• F— protection of low current circuits.
• M— protection of disconnecting devices and electric motors.
• R— protection of semiconductor devices.
• S— fast response during short circuit and medium response during overload.
• Tr— protection of transformers.

types and device

Low current inserts

These fuses are used to protect low-power electrical devices with a current consumption of up to 6 A.

The first number is the outer diameter, the 2nd is the length of the fuse.

• 3 x 15.
• 4 x 15.
• 5 x 20.
• 6 x 32.
• 7 x 15.
• 10 x 30.

Fork fuses

They are used for use in cars and protect their circuits from overloads. Plug inserts are manufactured for voltages up to 32 V. Appearance their designs are shifted to the side, since the contacts are on one side and the fusible part on the other.

• Miniature inserts.
• Regular.

Cork inserts

Used in residential buildings, operate at currents up to 63 A.

• DIAZED.
• NEOZED.

Such fuses are used for lighting devices, protection of household devices, meters, and low-power electric motors. They differ from tubular inserts in the method of fastening.

Tubular inserts

Such inserts are made in closed form with housings made of material - fiber, which forms a gas that creates high pressure, breaking the chain. Contacts.

1. Caps.
2. Rings.
3. Fiber.
4. The insert is fusible.

Blade fuses

The operating current reaches 1.25 kA. Standard sizes of knife types:

• 000 – up to 100 A.
• 00 – up to 160 A.
• 0 – up to 250 A.
• 1 – up to 355 A.
• 2 – up to 500 A.
• 3 – up to 800 A.
• 4 – up to 1250 A.

Quartz

This type of insert is current-limiting, does not form gases, and is used for indoor installation. Quartz fuses are designed for voltages up to 36 kilovolts.

1 – Cartridge (ceramics, glass).
2 – Fusible insert.
3 – Caps (metal).
4 - Filler.
5 – Index.

The cartridge is closed with caps, ensuring tightness. The filler has certain requirements:

• Durability (electrical).
• High thermal conductivity.
• Should not form gases.
• Should not absorb moisture.
• The filler particles must be of the strictly required size to avoid sintering or the inability to extinguish the arc.

Quartz sand meets these requirements. The fusible element is made of copper coated with silver. Due to its considerable length, the fusible element is wound in the form of a spiral.

Gas generating

This type includes collapsible fuses PR, firing inserts for external installation of PSN, exhaust PVT for transformers.

The PR insert is used for indoor installation in devices up to 1000 volts. It consists of:

1. The cartridge is made of fiber with brass rings around the edges. Brass caps are screwed onto the ends.
2. Caps.
3. Fuse element in the form of a zinc plate.
4. Contacts.

When the insert burns under the influence of an electric arc, a significant amount of gas is formed. Its pressure increases, the arc goes out in the gas flow. The insert is made in a V-shape, since during combustion of the bottleneck, a smaller amount of metal vapor is formed, which prevents the arc from extinguishing.

Thermal fuses

This type of insert is a disposable device. It serves to protect expensive equipment elements from overheating above the limit set temperature. Temperature-sensitive materials are placed inside the housing, which ensures the installation of inserts in circuits with high current.

The principle of operation is as follows. In normal mode, the insert has a resistance equal to zero. When the housing from the protected device heats up to the operating temperature, the heat-sensitive jumper is damaged, which breaks the power supply circuit of the device. After tripping, you need to replace the thermal fuse and eliminate the cause of the breakdown.

Such fuses have become popular in household electrical devices: toasters, coffee makers, irons, as well as in climate control equipment.

General Features

Fuses differ in their tripping properties from their rated current. Fuses have an inert response, so professionals often use them for selective protection together with electrical circuit breakers.

The rules govern the protection air lines so that the insert is triggered in 15 s. An important value is the destruction time of the conductor when working with a current exceeding the set value. To reduce this time, some fuse designs are pre-wired. tensioned spring. It separates the edges of the destroyed conductor to prevent the occurrence of an electric arc.

Fuse housings are made from durable ceramics. For low currents, inserts with glass housings are used. The insert body plays the role of the main part. A fusible element, an operation indicator, contacts, and a table with data are attached to it. The housing also acts as an arc extinction chamber.

Disadvantages of fuses

• Can be used once.
• Significant disadvantage fuse links is its device, which allows unscrupulous specialists to perform bypass surgery (use “bugs”). This may cause the wiring to catch fire.
• In 3-phase electric motor circuits, when one fuse trips, one phase disappears, which most often leads to engine malfunctions. In this case, it is advisable to use a phase control relay.
• It is possible to illegally install a fuse at a higher current rating.
• Phase imbalance may occur in 3-phase networks at significant currents.

Advantages of fuses

• In asymmetrical 3-phase circuits, in case of emergency on the 1st phase, the electric current will disappear only in this phase, the other phases will continue to supply power to consumers. At high currents, this situation should not be allowed, as this will lead to phase imbalance.
• Due to their low speed of action, fuses can be used for selectivity.
• The selectivity of the inserts themselves in a series circuit is much simpler to calculate compared to automatic fuses, since the rated currents of fuses connected in series must differ from each other by a factor of 1.6.
• The fuse design is much simpler than that of electric machine, therefore, mechanism failure is excluded. This provides a complete guarantee that the circuit will be disconnected during an accident.
• After replacing the fuse with a fusible element, protection is restored in the circuit with properties that satisfy the device manufacturer, in contrast to the use of a machine whose contacts may burn out, thereby changing the protection characteristics.

ELECTROSPETS

ELECTROSPETS

Fuse material

Fuse links are made of copper, zinc, lead or silver. The main technical data of these materials in terms of their applicability for fuse links are given in Table. 1.

In today's most advanced fuses, preference is given to copper inserts with a tin solvent. Zinc inserts are also widespread. Copper fuse inserts are the most convenient, simple and cheap. Improving their characteristics is achieved by fusing a tin ball in a certain place, approximately in the middle of the insert. Such inserts are used, for example, in the mentioned series of bulk fuses PN2. Tin melts at a temperature of 232° C, significantly lower than the melting point of copper, and dissolves the copper of the insert at the point of contact with it. The arc that appears in this case already melts the entire insert and is extinguished. The current circuit turns off.
Thus, fusing a tin ball results in the following.
Firstly, copper inserts begin to react with a time delay to such small overloads, to which they would not react at all in the absence of a solvent. For example, a copper wire with a diameter of 0.25 mm with a solvent melted at a temperature of 280 ° C in 120 minutes.
Secondly, at the same sufficiently high temperature (i.e., under the same load), inserts with a solvent react much faster than inserts without a solvent. For example, a copper wire with a diameter of 0.25 mm without a solvent at an average temperature of 1000 ° C melted in 120 minutes, and the same wire, but with a solvent at an average temperature of only 650 ° C, melted in just 4 minutes.
The use of a tin solvent makes it possible to have reliable and cheap copper inserts that operate at a relatively low operating temperature, have a relatively small volume and weight of metal (which favors the switching ability of the fuse) and at the same time have greater speed at high overloads and react with a time delay to relatively small overloads. The ratio Ip og:Iv for such inserts is relatively small (no more than 1.45), which facilitates the selection of conductors protected by such fuse-links from overloads.
Zinc is often used to make fuse links. In particular, such inserts are used in the mentioned series of PR2 fuses. Zinc inserts are more resistant to corrosion. Therefore, despite the relatively low melting point, for them, generally speaking, it would be possible to allow the same maximum operating temperature as for (copper 250°C) and design inserts with a smaller cross-section. However, the electrical resistance of zinc is approximately 3.4 times greater than that of copper. To maintain the same temperature, it is necessary to reduce energy losses in it, accordingly increasing its cross-section. The insert turns out to be much more massive. This, other things being equal, leads to a decrease in the switching capacity of the fuse. In addition, with a massive insert with a temperature of 250°C, it would not be possible to maintain the temperature of the cartridge and contacts at an acceptable level in the same dimensions. All this makes it necessary to reduce the maximum temperature of zinc inserts to 200°C, and therefore further increase the cross-section of the insert. As a result, fuses with zinc inserts of the same dimensions have significantly less resistance to short-circuit currents than fuses with copper inserts and tin solvents.
When there is a great need, a number of enterprises produce fuse links in their own electrical repair shops.
At the same time, the materials from which the fuse-link elements are made must be carefully calibrated and at least 10% of the finished fuse-links are selectively tested for minimum and maximum currents.
The minimum current is taken at which the fuse-link should not burn out in less than 1 hour. Typically this current is equal to 1.3-1.5 of its rated current, i.e. Imin=(l.3-1.5)Inom.
The maximum current is taken at which the fuse link must burn out in less than 1 hour; it is usually (l.6-2.l)Inom.
It is unacceptable to use home-made inserts, since at best they protect the installation only from short-circuit currents. To fasten the zinc fuse link, a steel washer of increased diameter and a spring washer must be used. In the absence of these washers, the zinc is gradually squeezed out from under the contact bolt and weakens the contact. A copper insert cannot be installed in a PR fuse holder without a tin solvent, since at the high melting temperature of the copper insert, the fiber cartridge is quickly destroyed.

Burnt-out fuse links should be replaced with spare factory-calibrated ones. If there are none, they can be temporarily replaced with pre-prepared wires designed for a certain current. The diameters and materials of the wires are given in Table 2.

Any electrical circuit consists of individual elements. Each of them is characterized by certain current values ​​at which the element is operational. Increasing the current above these values ​​may cause damage to the element. This is due to unacceptable 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 various designs allow you to 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 fuse, the heat generated 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.

• Time-current characteristic - main parameter fuse link, according to 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

From special polymer material a block is made 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.

Fuses are used everywhere and everywhere - they are in technology, in a wide variety of electrical devices, cars, and industrial equipment. There are many types of these elements. Why are they needed and what are their features? Let's look at the main types of fuses.

Characteristic

Fuse is a general term that is used quite consistently in the electrical field. This part provides protection for wires, equipment and electrical networks.

The fuse is a switching product. What is its purpose? The fuse is designed to protect the electrical network from high currents and short circuits. The principle of operation of the part is very simple - in the event of the formation of supercurrents, an element specially designed for this purpose is destroyed. Often this is a fusible link. This is how all types of glass fuses are designed.

These inserts are a mandatory element, without which no type of safety elements is possible. There is also a special arc extinguishing device inside it. Fuse inserts are made of porcelain or fiber casings and are fixed into special parts that conduct electric current. Elements designed for low currents may not have a housing at all.

Melting

These are the most common types of fuses for household use. This is probably the only element that is easiest to diagnose for serviceability. To do this, you just need to look at the part in the light - you will see whether the insert melt is intact or not.

These parts are manufactured in a glass case.

Fusible Tubular Ceramic

This element is practically no different from a glass product. The only difference is the material from which the case is made. But these parts are not so comfortable to use - they can no longer be diagnosed “in the light”. To check, you must use testers or multimeters.

PVD fuse link

Fast acting fuses

These products are no different from the rest. The only difference is that when a short circuit occurs, the fusible part burns out very quickly.

SMD

These products can be found in electronic devices. They are very miniature. The principle of operation and purpose of fuses is to protect equipment from high currents, which they do an excellent job of.

Self-healing

This is enough interesting solutions. A self-resetting fuse is a part containing special plastic inside. As long as the plastic insert is cold, it can conduct electricity. As soon as the insert warms up to a certain temperature, its conductive properties are lost due to an increase in resistance.

After cooling, current will again be able to pass through the product. The advantage of these parts is that after a burnout there is no need to replace the element. The industry produces these products in various types. They are suitable for soldering using surface or surface mount technology. These types of fuses are mainly used in low-power circuits.

Explosive

If everyone knows all of the above products, then the explosive fuse is a rare group. The process of burning out a part is ensured by a fairly effective sound. A special one that is attached to a conductive part explodes. Special sensors are responsible for this. The latter monitor the current in the electrical circuit. These are very precise fuses, since they are practically independent of the characteristics of the metal on the conductive part. This element depends on the accuracy of the current sensor.

Other types of fuses

To work in circuits, special autogas, gas products, as well as liquid-type elements are used. There are even firing fuses. You cannot see them in everyday life - they are professional, powerful equipment.

Markings and symbols

Each manufacturer produces fuses under a specific code or article number. The fuse number allows you to find and clarify in catalogs specifications. Often these codes can be found on product bodies. The code can also be applied to the metal part. In addition to codes, basic data can also be indicated on the case - this is the rated current in A, rated voltage in V, disconnecting characteristics or design features. Using this data, you can determine the purpose of the fuses.

So, the rated current is the maximum permissible value at which the part can function normally for a long time.

Rated voltages are the maximum permissible voltage at which a part will safely break the circuit in the event of a short circuit or network overload.

Breaking capacity is called maximum currents. With them, the fuse will work, but its housing will not be destroyed.

Characteristics are the dependence of the time at which the fusible element collapses on the current that flows through the part. Different types fuses according to their characteristics are combined into groups according to application features and response speed.

Typically these characteristics are indicated on power parts. Letters of the Latin alphabet are used for designation. The first is the breaking capacity. So, G is the full range, the part is capable of protecting the circuit from both overload and short circuit. A - the range is partial, and these types of fuses only protect against short circuits.

The second letter denotes the types of chain:

• G - general purpose circuit.
• L - protection of cables and distribution systems.
• M - protection of circuits in electric motors.
• Tr is a fuse capable of protecting a transformer network.

Items with the letter R are used in conjunction with power semiconductor equipment. And PV will be able to provide protection for solar panels.

So, we looked at what types of fuses there are and what markings they have.

Fuse is an installation product designed to protect electrical appliances by cutting off the supply of electricity to them when the permissible current value is exceeded by melting the calibrated wire installed in the fuse.

To protect electrical wiring and expensive radio equipment from short circuits, current surges in the supply network and ensure the safe operation of electrical appliances, fuses are widely used. They are released different designs, standard sizes and for any protection currents.

The considered fuse repair technology, if all conditions are met, will ensure its protective function. But not everyone has experience working with a soldering iron and measuring wire diameter. And in any case, an industrial fuse will work more reliably.

Previously, apartment electrical wiring was also protected exclusively with fuses installed in plugs. Currently, more reliable reusable short circuit protection devices are used to protect electrical wiring - circuit breakers. In electrical appliances, nothing better protection against short circuits than a fuse has yet been invented. The use of fuses in cars is especially important, since they are the only reliable and cheap means of protection against short circuits.

Conventional graphic symbol
fuse

The conventional graphic designation of a fuse in the diagrams is similar to the designation of resistance, and differs only in that the line passes through the middle of the rectangle without breaking. Next to the symbol, the letter Pr is usually written. or F. Sometimes the diagrams simply write thermal fuse or fuse. After the letter, the protection current of the fuse is often indicated, for example F 1 A, means that the circuit has a fuse for a protection current of 1 ampere.

During operation, fuses fail and have to be replaced with new ones. It is believed that fuses cannot be repaired. But if you approach the repair process competently, then almost any fuse can be successfully repaired and reused. After all, the fuse body remains intact, and only a thin calibrated wire located inside the body burns out. If the burnt wire is replaced with the same one, the fuse will continue to serve.

How the fuse works in the video

When passing electric current less than the maximum permissible, the calibrated wire connecting the fuse contacts heats up to a temperature of about 70˚C. If the current exceeds the fuse rating, the wire begins to heat up more strongly and when the melting temperature of the metal from which it is made is reached, it melts, the electrical circuit is broken, and the flow of current stops.

That's why the fuse is called a fuse or fusible link. The video is presented in slow motion so that you can clearly see how the wire in the fuse burns out. In real conditions, the wire in the fuse burns out almost instantly.

The fuse protects against excess current in the circuit and the voltage of the supply network in which it is installed does not matter, it can be a 1.5 V battery, a 12 V or 24 V car battery, a 220 V AC network, a three-phase network 380 V. That is, you can install the same fuse, for example rated 1 A, in the fuse block of the car, in the flashlight, and in switchboard 380 V. All types of fuses differ only in appearance and design, but work on the same principle - when the specified current in the circuit is exceeded, the wire in the fuse melts due to heating.

There are two main reasons for fuse failure, due to surges in the supply voltage or a breakdown inside the radio equipment itself. Rarely, fuse failures also occur due to poor quality.

Many people think that the fuse cannot be repaired. But it is not so. In an emergency situation, when there is no spare at hand and, for example, because a car on the road or an amplifier refuses to work, and the musical accompaniment of a school ball or wedding is disrupted, and all the shops are already closed, there is no choice.

With the right approach, you can successfully restore a blown fuse for temporary use until it is replaced with a new one, preserving its protective functions. Often such problems are solved by simply closing the contacts of the fuse holder with any available wire, or even worse, simply inserting a nail or a piece of thick wire instead of the fuse. Such a decision can completely ruin everything and contribute to a fire.

Fuse Types

According to their purpose and design, fuses are of the following types:

• Plugs (mainly used to protect electrical wiring and devices in cars);
• With low-current inserts to protect electrical appliances with current consumption up to 6 amperes;
• Cork (installed in panels of residential buildings, designed for protection current up to 63 amperes);
• Knife type (used in industry to protect networks with current consumption up to 1250 amperes);
• Gas generating;
• Quartz.

The repair technology discussed in the article is intended for restoring fork fuses, with low-current inserts, plug and blade type fuses.

Tubular fuses

A fuse of a tubular design is a glass or ceramic tube, closed at the ends with metal caps, which are connected to each other by a wire of calibrated diameter running inside the tube. You can see the appearance of tubular fuses in the photograph.

The wire is spot welded to the caps or soldered with solder. In fuses designed for very high currents, the cavity inside the tube is often filled with quartz sand.

Automotive fuses

Fuses in cars rarely fail. Usually only in cases where the equipment fails.

Most often when the headlight bulbs burn out. The fact is that when the filament of a light bulb breaks, a Voltaic arc is formed, the filament burns out and becomes shorter, the resistance sharply decreases and the current increases many times over.

A blown fuse in a car should be replaced with a fuse of the same rating, but it can also be repaired by replacing the blown wire in the fuse with a copper wire of the appropriate diameter. The voltage of the car's on-board network does not matter. The main thing is the correspondence of the protection current. If it is difficult to determine the rating of a blown car fuse, then you can use color coding.

Color coding of automotive fuses

Formula for calculating fuse wire diameter
according to the power of the electrical appliance

Power is often indicated on labels affixed to products. If the power consumption is indicated on the product, then the rated current of the fuse can be calculated using the formula below.

But it is much more convenient to use ready-made data from tables. Please note that the first table is used to select the fuse rating of products powered from a 220 V household power supply, and the second table is for products used in cars with an on-board voltage of 12 V.

Table for selecting the fuse rating depending on the power consumption of the electrical appliance at a supply voltage of 220 V

Let's look at an example of how to choose a fuse.
The TV stopped working after a thunderstorm. It has been determined that the fuse has blown. Its denomination is not known. On the back cover label it is written that the power consumption is 120 W, sometimes it is written as 120 VA. This is a designation of the same power, but according to the standards different countries. According to the table, it turns out that for electrical appliances with a maximum power consumption of 120 W (the closest value is 150 W) there is a 1 A fuse.

The method for selecting a fuse to protect the on-board electrical wiring of a car is no different from the choice for 220 V household electrical wiring.

Table for selecting the fuse rating depending on the power consumption of the electrical appliance at a supply voltage of 12 V (vehicle on-board network)

If after two replacements the fuses blow out each time, it means that the electrical appliance is damaged and requires repair. An attempt to set a fuse to a higher current can only cause further damage to the product, even to the point of being beyond repair.

Fuse current calculator

If the tables do not contain data for your case, for example, the product’s supply voltage is 24 V or 110 V, then you can do it yourself using the following online calculator perform the calculation.

When calculating on a calculator you will get the exact current value. For reliable operation of the fuse, it is necessary that its rating be at least 5% higher. For example, if a calculated current value of 1 A is obtained, then you need to take a fuse of the highest closest rating from the standard range, that is, 2 A.

Sometimes attempts to determine the fuse rating by reading the information do not work. There are no inscriptions on the electrical device; the markings on the fuse are unreadable. If you have an ammeter and experience working with it, then by removing the fuse and connecting the ammeter to the contacts of the block in which the fuse was installed, you can measure the current and thereby determine its rating.

But there is a pitfall here. If the fuse fails due to a malfunction of an electrical device, then the current may be much greater than it should be, in addition, the measuring device may also be damaged.

Calculation of fuse wire diameter

To repair the fuse, it is necessary to replace the burnt wire. In the production of fuses in factories, depending on the current value and speed, calibrated silver, copper, aluminum, nickel, tin, lead and wires made of other metals are used.

For making a fuse at home, only red copper of calibrated diameter is available. All electrical wires are made of copper, and the more elastic the wire, the thinner the conductors and the greater the number of them. Therefore, all the technology proposed below is focused on the application copper wire.

When choosing a fuse for equipment, developers use simple law. The fuse current must be greater than the maximum consumed by the product. For example, if the maximum current consumption of the amplifier is 5 amperes, then the fuse is selected at 10 amperes. The first thing you need to do is find the markings on the fuse body, from which you can find out what current it is designed for. Often the current value is written on the product body, next to the location where the fuse is installed. Then, from the table below, determine what diameter wire is needed.

Tables for choosing wire diameter
depending on fuse protection current

For repairing fuses with protection current from 0.25 to 50 amperes

For repairing fuses with protection currents from 60 to 300 Amps

Formula for calculating the diameter of copper wire
for fuse

To determine more exact values diameter of copper wire to repair the fuse, or if a fuse is required for a protection current whose value is not in the table, you can use the formula below.

How to measure wire diameter

The diameter of a thin wire is best measured with a micrometer. If you don’t have a micrometer at hand to measure the diameter of the wire, you can use an ordinary ruler.

You need to wind 10-20 turns per turn of wire on a ruler, divide the number of closed millimeters by the number of wound turns. Get the diameter. For example, I wound 10 turns of wire and they covered 6.5 mm. Divide 6.5 by 10. The diameter of the wire is equal to 0.65 mm. 0.05 mm is occupied by insulation. Therefore, the actual diameter is 0.6 mm.

Such a wire is suitable for making a 30 A fuse. The wire was wound thick for greater clarity. The more turns you wind on the ruler, the more accurate the measurement result will be. You need to wind at least one centimeter. If you have a short length of wire, then wind it around any rod, for example, a screwdriver, toothpick or pencil, and measure the width of the winding with a ruler.

You can process the measurement results using an online calculator. To determine the diameter of the wire, just enter the winding width, the number of turns in the windows and click “Calculate wire diameter”.

DIY fuse repair

Tube fuse repair

The first one is the simplest. The wire is stripped to a shine and wound several turns onto each cup, then the fuse is inserted into the holder. This method is not reliable and can only be used as a temporary measure. Due to its simplicity, it allows you to quickly check the serviceability of an electrical appliance. If the wire melts when turned on, it means the fuse is not the problem, and more qualified repairs are required.

The second method is somewhat more complicated. But it also does not require soldering. You need to warm up the cups one by one with a lighter or gas stove and holding them through the fabric with your hands, remove them from the glass tube. You can also heat it with a soldering iron. To ensure good contact, the inside of the cup must be thoroughly cleaned of any glue residue.

Pass the wire stripped of insulation through the tube diagonally, bend its ends along the tube and put the cups in place. The fuse has been repaired.

The third method is essentially the same as the first two. But a repaired fuse is practically no different from a new one. The repair is carried out as follows.

When making a fuse, factory calibrated wire is threaded through the holes in the ends of the cups and fixed with solder. In order to insert a new wire, you need to heat the ends of the cups with a soldering iron and use a toothpick or a sharpened wooden stick to free the holes in the ends of the cups from solder. Next, perform the factory operation described above.

There are holes in the cups of very small diameter and it is difficult to clean them from solder. Then, if technically possible, it is easier to drill holes with a drill with a diameter of 1-2 mm or widen them with a faceted awl

The proposed technology for repairing fuses and fuse links can be successfully used to restore almost any type of fuses.

Blade type car fuse repair

The technology for repairing a car fuse is no different from the technology for repairing a tubular fuse; it is even simpler, since there is no need to disassemble it.

First, you need to use sandpaper or a file to clean the fuse blades at its base with a strip of a few millimeters and tin these places with solder.

When tinning, I encountered the fact that when using alcohol-rosin flux, the solder did not want to spread over the surface of the knives. I had to use FIM flux, intended for soldering copper, silver, constantan, platinum and ferrous metals. The basis of the flux is phosphoric acid. I always use it for soldering if rosin is not suitable. Residues of FIM flux are removed by washing with water.

The fuse was designed for a protection current of 10 A, therefore, in accordance with the table above, a wire ⌀0.25 mm was taken for repair. The wire was shaped into a loop, as shown in the photo, and its ends were tinned with solder.

After all preparatory work All that remains is to bring the loop of wire inside the fuse body and solder the ends to the legs.

Spread solder can be cut off with a knife, removed with sandpaper, or filed off with a file.

The car fuse has been repaired and can now be reused to protect circuits in the car's electrical wiring. If, after installing the repaired fuse, it blows again, then you need to look for a fault in the vehicle’s electrical equipment.

How to make a blown fuse indicator with your own hands

There are car fuses on sale with a fault indicator. A miniature incandescent light bulb or LED is built into the fuse housing, which begins to glow when the fuse blows. You can assemble such a blown auto fuse indicator with your own hands using the electrical diagram shown in the photo below.

To do this, it is enough to connect in parallel to the fuse contacts, any LED VD1 through a current-limiting resistor R1 or a miniature light bulb rated for a voltage of 12 V. The fuse blown indicator can be mounted either in the fuse body or installed on the block of its holder. The second option is preferable, since when replacing the fuse, the indicator will remain in place. The indicator will not light if the fuse is blown and there is no load connected.

The circuit shown in the photograph indicating that a fuse has blown or a circuit breaker has tripped can also work successfully in a household electrical network with a supply voltage of 220 V.

It is enough to increase the value of resistor R1 to 300-500 kOhm and to protect the LED VD1 from breakdown by reverse voltage, supplement the circuit with a diode VD2 of any type, designed for a reverse voltage of at least 300 V. For example, the widely used domestic diode KD109B or imported 1N4004 will do.

For network alternating current 220 V can be used to indicate a blown fuse or circuit breaker using a neon light bulb.