Wiring diagram of the induction cooker. induction melting furnace

An induction furnace is often used in the field of metallurgy, so this concept is well known to people who are more or less connected with the process of smelting various metals. The device allows you to convert electricity generated by a magnetic field into heat.

Such devices are sold in stores at a fairly high price, but if you have minimal skills in using a soldering iron and can read electronic circuits, then you can try to make an induction furnace with your own hands.

A homemade device is unlikely to be suitable for complex tasks, but it will cope with basic functions. You can assemble the device on the basis of a working welding inverter from transistors, or on lamps. The most productive in this case is the device on the lamps due to the high efficiency.

The principle of operation of the induction furnace

The heating of the metal placed inside the device occurs by the transition of electromagnetic pulses into heat energy. Electromagnetic impulses are produced by a coil with turns of copper wire or pipe.

Scheme of the induction furnace and heating schemes

When the device is connected, an electric current begins to pass through the coil, and an electric field appears around it, changing its direction over time. For the first time, the performance of such an installation was described by James Maxwell.

The object to be heated must be placed inside the coil or close to it. The target object will be pierced by a flux of magnetic induction, and a vortex-type magnetic field will appear inside. Thus, inductive energy will turn into heat.

Varieties

Furnaces on an induction coil are usually divided into two types depending on the type of construction:

• Channel;
• Crucible.

In the first devices, the metal for melting is located in front of the induction coil, and in the furnaces of the second type it is placed inside it.

You can assemble the oven by following the steps below:

1. We bend the copper pipe in the form of a spiral. In total, it is necessary to make about 15 turns, the distance between which should be at least 5 mm. Inside the spiral, a crucible should be freely located, where the smelting process will take place;
2. We make a reliable case for the device, which should not conduct electric current, and must withstand high air temperatures;
3. Chokes and capacitors are assembled according to the scheme indicated above;
4. A neon lamp is connected to the circuit, which will signal that the device is ready for operation;
5. A capacitor is also soldered to adjust the capacitance.

Heating use

Induction furnaces of this type can also be used for space heating. Most often they are used together with a boiler, which additionally produces cold water heating. In fact, designs are used extremely rarely due to the fact that, as a result of electromagnetic energy losses, the efficiency of the device is minimal.

Another drawback is based on the consumption of large amounts of electricity by the device during operation, because the device is classified as economically unprofitable.

System cooling

A self-assembled device must be equipped with a cooling system, since during operation all components will be exposed to high temperatures, the structure may overheat and break. Store-bought ovens are cooled with water or antifreeze.

When choosing a cooler for the home, preference is given to options that are most beneficial for implementation from an economic point of view.

For home ovens, you can try using a conventional blade fan. Pay attention to the fact that the device should not be too close to the oven, as the metal parts of the fan negatively affect the performance of the device, and can also open the vortex flows and reduce the performance of the entire system.

Precautions for using the device

When working with the device, you must adhere to the following rules:

• Some elements of the installation, as well as the metal that melts, are exposed to strong heat, as a result of which there is a risk of getting burned;
• When using a lamp oven, be sure to place it in a closed case, otherwise there is a high probability of electric shock;
• Before working with the device, remove all metal elements and complex electronic devices from the working area of ​​the device. The device should not be used by people who have a pacemaker installed.

The induction type metal melting furnace can be used in tinning and forming metal parts.

A home-made installation is easy to adjust to work in specific conditions by changing some settings. If you follow the indicated schemes when assembling the structure, as well as follow the elementary safety rules, a home-made device will practically not be inferior to store-bought household appliances.

Read in the article

The principle of operation of the induction heater

Induction heating is not possible without the use of three main elements:

• inductor;
• generator;
• heating element.

An inductor is a coil, usually made of copper wire, that generates a magnetic field. An alternator is used to produce a high frequency stream from a standard 50 Hz household power stream. A metal object is used as a heating element, capable of absorbing thermal energy under the influence of a magnetic field.

If you connect these elements correctly, you can get a high-performance device that is perfect for heating a liquid coolant and heating a house. With the help of a generator, an electric current with the necessary characteristics is supplied to the inductor, i.e. on a copper coil. When passing through it, the flow of charged particles forms a magnetic field.

The principle of operation of induction heaters is based on the occurrence of electric currents inside conductors that appear under the influence of magnetic fields.

The peculiarity of the field is that it has the ability to change the direction of electromagnetic waves at high frequencies. If any metal object is placed in this field, it will begin to heat up without direct contact with the inductor under the influence of the created eddy currents.

The high-frequency electric current flowing from the inverter to the induction coil creates a magnetic field with a constantly changing vector of magnetic waves. The metal placed in this field heats up quickly

The lack of contact makes it possible to make energy losses during the transition from one type to another negligible, which explains the increased efficiency of induction boilers.

To heat water for the heating circuit, it is enough to ensure its contact with a metal heater. Often, a metal pipe is used as a heating element, through which a stream of water is simply passed. Water simultaneously cools the heater, which significantly increases its service life.

The electromagnet of an induction device is obtained by winding a wire around a core of a ferromagnet. The resulting induction coil heats up and transfers heat to the heated body or to the coolant flowing nearby through the heat exchanger

Literature

• Babat G. I., Svenchansky A. D. Electrical industrial ovens. - M. : Gosenergoizdat, 1948. - 332 p.
• Burak Ya. I., Ogirko I. V. Optimal Heating of a Cylindrical Shell with Temperature-Dependent Characteristics of the Material // Mat. methods and fiz.-mekh. fields. - 1977. - Issue. five . - S. 26-30.
• Vasiliev A.S. Lamp generators for high-frequency heating. - L.: Mashinostroenie, 1990. - 80 p. - (Library of high-frequency thermist; Issue 15). - 5300 copies. - ISBN 5-217-00923-3.
• Vlasov V.F. Radio engineering course. - M. : Gosenergoizdat, 1962. - 928 p.
• Izyumov N. M., Linde D. P. Fundamentals of radio engineering. - M. : Gosenergoizdat, 1959. - 512 p.
• Lozinsky M. G. Industrial application of induction heating. - M.: Publishing House of the Academy of Sciences of the USSR, 1948. - 471 p.
• The use of high-frequency currents in electrothermy / Ed. A. E. Slukhotsky. - L.: Mashinostroenie, 1968. - 340 p.
• Slukhotsky A. E. Inductors. - L.: Mashinostroenie, 1989. - 69 p. - (Library of high-frequency thermist; Issue 12). - 10,000 copies. - ISBN 5-217-00571-8.
• Vogel A. A. Induction Method for Holding Liquid Metals in Suspension / Ed. A. N. Shamova. - 2nd ed., corrected. - L.: Mashinostroenie, 1989. - 79 p. - (Library of high-frequency thermist; Issue 11). - 2950 copies. - .

Operating principle

The latter option, most commonly used in heating boilers, has become in demand due to the simplicity of its implementation. The principle of operation of the induction heating unit is based on the transfer of magnetic field energy to the coolant (water). The magnetic field is formed in the inductor. Alternating current, passing through the coil, creates eddy currents that transform energy into heat.

The principle of operation of the installation of induction heating

The water supplied through the lower pipe to the boiler is heated by energy transfer, and exits through the upper pipe, getting further into the heating system. A built-in pump is used to create pressure. Constantly circulating water in the boiler does not allow the elements to overheat. In addition, during operation, the heat carrier vibrates (at a low noise level), due to which scale deposits on the inner walls of the boiler are impossible.

Induction heaters can be implemented in various ways.

Power calculation

Since the induction method of steel melting is less expensive than similar methods based on the use of fuel oil, coal and other energy carriers, the calculation of an induction furnace begins with the calculation of the power of the unit.

The power of the induction furnace is divided into active and useful, each of them has its own formula.

As initial data you need to know:

• the capacity of the furnace, in the case considered for example, it is equal to 8 tons;
• unit power (its maximum value is taken) - 1300 kW;
• current frequency - 50 Hz;
• the productivity of the furnace plant is 6 tons per hour.

It is also required to take into account the melted metal or alloy: by condition it is zinc. This is an important point, the heat balance of melting cast iron in an induction furnace, as well as other alloys.

Useful power, which is transferred to the liquid metal:

• Рpol \u003d Wtheor × t × P,
• Wtheor - specific energy consumption, it is theoretical, and shows the overheating of the metal by 10C;
• P - productivity of the furnace plant, t/h;
• t - overheating temperature of an alloy or a metal billet in a bath furnace, 0С
• Рpol \u003d 0.298 × 800 × 5.5 \u003d 1430.4 kW.

Active power:

• P \u003d Rpol / Yuterm,
• Rpol - taken from the previous formula, kW;
• Yuterm - the efficiency of the foundry furnace, its limits are from 0.7 to 0.85, on average they take 0.76.
• P \u003d 1311.2 / 0.76 \u003d 1892.1 kW, the value is rounded up to 1900 kW.

At the final stage, the power of the inductor is calculated:

• Rind \u003d P / N,
• P is the active power of the furnace plant, kW;
• N is the number of inductors provided on the furnace.
• Rind \u003d 1900 / 2 \u003d 950 kW.

The power consumption of an induction furnace when melting steel depends on its performance and the type of inductor.

Furnace components

So, if you are interested in a do-it-yourself induction mini-oven, then it is important to know that its main element is a heating coil. In the case of a homemade version, it is enough to use an inductor made of a bare copper tube with a diameter of 10 mm

For the inductor, an inner diameter of 80-150 mm is used, and the number of turns is 8-10. It is important that the turns do not touch, and the distance between them is 5-7 mm. Parts of the inductor must not come into contact with its screen, the minimum clearance must be 50 mm.

If you are going to do-it-yourself induction furnace, then you should know that water or antifreeze is cooling the inductors on an industrial scale. In the case of low power and short operation of the created device, it is possible to do without cooling. But during operation, the inductor becomes very hot, and scale on copper can not only drastically reduce the efficiency of the device, but also lead to a complete loss of its performance. It is impossible to make an inductor with cooling on your own, so it will need to be replaced regularly. Forced air cooling must not be used, since the fan housing located close to the coil will “attract” EMF to itself, which will lead to overheating and a decrease in the efficiency of the furnace.

The problem of induction heating of workpieces made of magnetic materials

If the inverter for induction heating is not a self-oscillator, does not have a self-tuning circuit (PLL) and operates from an external master oscillator (at a frequency close to the resonant frequency of the "inductor - compensating capacitor bank" oscillatory circuit). At the moment a workpiece made of magnetic material is introduced into the inductor (if the workpiece dimensions are large enough and commensurate with the dimensions of the inductor), the inductance of the inductor increases sharply, which leads to an abrupt decrease in the natural resonant frequency of the oscillatory circuit and its deviation from the frequency of the master oscillator. The circuit goes out of resonance with the master oscillator, which leads to an increase in its resistance and an abrupt decrease in the power transmitted to the workpiece. If the power of the unit is controlled by an external power supply, then the natural reaction of the operator is to increase the supply voltage of the unit. When the workpiece is heated to the Curie point, its magnetic properties disappear, the natural frequency of the oscillatory circuit returns back to the frequency of the master oscillator. The resistance of the circuit decreases sharply, the current consumption increases sharply. If the operator does not have time to remove the increased supply voltage, the unit overheats and fails.
If the installation is equipped with an automatic control system, then the control system should monitor the transition through the Curie point and automatically reduce the frequency of the master oscillator, adjusting it to resonance with the oscillatory circuit (or reduce the supplied power if the frequency change is unacceptable).

If non-magnetic materials are being heated, then the above does not matter. The introduction of a blank made of non-magnetic material into the inductor practically does not change the inductance of the inductor and does not shift the resonant frequency of the working oscillatory circuit, and there is no need for a control system.

If the dimensions of the workpiece are much smaller than the dimensions of the inductor, then it also does not greatly shift the resonance of the working circuit.

induction cookers

Main article: Induction cooker

Induction cooker- an electric kitchen stove that heats up metal utensils with induced eddy currents generated by a high-frequency magnetic field, with a frequency of 20-100 kHz.

Such a stove has a high efficiency compared to heating elements of electric stoves, since less heat is spent on heating the case, and besides, there is no acceleration and cooling period (when the energy generated, but not absorbed by the dishes, is wasted).

Induction Melting Furnaces

Main article: Induction crucible furnace

Induction (non-contact) melting furnaces - electric furnaces for melting and overheating metals, in which heating occurs due to eddy currents that occur in a metal crucible (and metal), or only in metal (if the crucible is not made of metal; this method of heating is more efficient if the crucible is poorly insulated).

It is used in foundry shops of factories, as well as in precision casting shops and repair shops of machine-building plants to obtain high quality steel castings. It is possible to melt non-ferrous metals (bronze, brass, aluminum) and their alloys in a graphite crucible. The induction furnace works on the principle of a transformer, in which the primary winding is a water-cooled inductor, the secondary and at the same time load is the metal in the crucible. The heating and melting of the metal occur due to the currents flowing in it, which arise under the influence of the electromagnetic field created by the inductor.

History of induction heating

The discovery of electromagnetic induction in 1831 belongs to Michael Faraday. When a conductor moves in the field of a magnet, an EMF is induced in it, just as when a magnet moves, the lines of force of which intersect the conducting circuit. The current in the circuit is called inductive. The inventions of many devices are based on the law of electromagnetic induction, including the determining ones - generators and transformers that generate and distribute electrical energy, which is the fundamental basis of the entire electrical industry.

In 1841, James Joule (and, independently of him, Emil Lenz) formulated a quantitative estimate of the thermal effect of electric current: “The power of heat released per unit volume of the medium during the flow of electric current is proportional to the product of the density of the electric current and the magnitude of the electric field strength” (Joule’s law - Lenz). The thermal effect of the induced current gave rise to the search for devices for non-contact heating of metals. The first experiments on heating steel using inductive current were made by E. Colby in the USA.

The first successfully operating so-called. The channel induction furnace for steel melting was built in 1900 by Benedicks Bultfabrik in Gysing, Sweden. In the respectable magazine of that time "THE ENGINEER" on July 8, 1904, the famous appeared, where the Swedish inventor engineer F. A. Kjellin talks about his development. The furnace was powered by a single-phase transformer. Melting was carried out in a crucible in the form of a ring, the metal in it represented the secondary winding of a transformer powered by a current of 50-60 Hz.

The first 78 kW furnace was put into operation on March 18, 1900 and proved to be very uneconomical, since the melting capacity was only 270 kg of steel per day. The next furnace was manufactured in November of the same year with a capacity of 58 kW and a capacity of 100 kg for steel. The furnace showed high profitability, the melting capacity was from 600 to 700 kg of steel per day. However, wear due to thermal fluctuations was at an unacceptable level, frequent lining changes reduced the resulting efficiency.

The inventor came to the conclusion that for maximum melting performance, it is necessary to leave a significant part of the melt during discharge, which avoids many problems, including lining wear. This method of smelting steel with a residue, which began to be called "bog", has survived to this day in some industries where large-capacity furnaces are used.

In May 1902, a significantly improved furnace with a capacity of 1800 kg was put into operation, the drain was 1000-1100 kg, the balance was 700-800 kg, the power was 165 kW, the steel melting capacity could reach up to 4100 kg per day! Such an energy consumption result of 970 kWh/t impresses with its efficiency, which is not much inferior to the modern productivity of about 650 kWh/t. According to the inventor's calculations, out of a power consumption of 165 kW, 87.5 kW went into losses, the useful thermal power was 77.5 kW, and a very high overall efficiency of 47% was obtained. Profitability is explained by the ring design of the crucible, which made it possible to make a multi-turn inductor with low current and high voltage - 3000 V. Modern furnaces with a cylindrical crucible are much more compact, require less capital investment, are easier to operate, equipped with many improvements over a hundred years of their development, but the efficiency is increased insignificant. True, the inventor in his publication ignored the fact that electricity is paid not for active power, but for full power, which at a frequency of 50-60 Hz is approximately twice as high as active power. And in modern furnaces, reactive power is compensated by a capacitor bank.

With his invention, the engineer F. A. Kjellin laid the foundation for the development of industrial channel furnaces for melting non-ferrous metals and steel in the industrial countries of Europe and America. The transition from 50-60 Hz channel furnaces to modern high-frequency crucible furnaces lasted from 1900 to 1940.

Heating system

In order to make an induction heater, knowledgeable craftsmen use a simple welding inverter that converts direct voltage to alternating voltage. For such cases, a cable with a cross section of 6-8 mm is used, but not standard for welding machines of 2.5 mm.

Such heating systems must necessarily be of a closed type, and control is automatic. For other safety, you need a pump that will circulate through the system, as well as an air bleed valve. Such a heater must be protected from wooden furniture, as well as from the floor and ceiling at least 1 meter.

Implementation at home

Induction heating has not yet sufficiently conquered the market due to the high cost of the heating system itself. So, for example, for industrial enterprises, such a system will cost 100,000 rubles, for domestic use - from 25,000 rubles. and higher. Therefore, the interest in circuits that allow you to create a home-made induction heater with your own hands is quite understandable.

heating induction boiler

Transformer based

The main element of the induction heating system with a transformer will be the device itself, which has a primary and secondary windings. Vortex flows will form in the primary winding and create an electromagnetic induction field. This field will affect the secondary, which is, in fact, an induction heater, physically implemented in the form of a heating boiler body. It is the secondary short-circuited winding that transfers energy to the coolant.

Secondary short-circuited winding of the transformer

The main elements of the induction heating installation are:

• core;
• winding;
• two types of insulation - thermal and electrical insulation.

The core is two ferrimagnetic tubes of different diameters with a wall thickness of at least 10 mm, welded into each other. A toroidal winding of copper wire is made along the outer tube. It is necessary to impose from 85 to 100 turns with an equal distance between the turns. Alternating current, changing in time, creates vortex flows in a closed circuit, which heat the core, and hence the coolant, by induction heating.

Using high frequency welding inverter

An induction heater can be created using a welding inverter, where the main components of the circuit are an alternator, an inductor and a heating element.

The generator is used to convert the standard 50 Hz mains frequency into a higher frequency current. This modulated current is applied to a cylindrical inductor, where copper wire is used as a winding.

Copper wire for winding

The coil creates an alternating magnetic field, the vector of which changes with the frequency set by the generator. The created eddy currents, induced by the magnetic field, heat the metal element, which transfers energy to the coolant. Thus, another do-it-yourself induction heating scheme is implemented.

A heating element can also be created with your own hands from a cut metal wire about 5 mm long and a piece of a polymer pipe into which the metal is placed. When installing valves at the top and bottom of the pipe, check the filling density - there should be no free space. According to the scheme, about 100 turns of copper wiring are superimposed on top of the pipe, which is the inductor connected to the generator terminals. Induction heating of copper wire occurs due to eddy currents generated by an alternating magnetic field.

Note: Do-it-yourself induction heaters can be made according to any scheme, the main thing to remember is that it is important to carry out reliable thermal insulation, otherwise the efficiency of the heating system will drop significantly. .

Advantages and disadvantages of the device

The “pluses” of the vortex induction heater are numerous. This is a simple circuit for self-production, increased reliability, high efficiency, relatively low energy costs, long service life, low probability of breakdowns, etc.

The performance of the device can be significant; units of this type are successfully used in the metallurgical industry. In terms of the rate of heating of the coolant, devices of this type confidently compete with traditional electric boilers, the water temperature in the system quickly reaches the required level.

During the operation of the induction boiler, the heater vibrates slightly. This vibration shakes off limescale and other possible contaminants from the walls of the metal pipe, so such a device rarely needs to be cleaned. Of course, the heating system must be protected from these contaminants with a mechanical filter.

The induction coil heats the metal (pipe or pieces of wire) placed inside it using high frequency eddy currents, contact is not necessary

Constant contact with water also minimizes the likelihood of heater burnout, which is a fairly common problem for traditional boilers with heating elements. Despite the vibration, the boiler operates exceptionally quietly; additional noise insulation at the installation site of the device is not required.

Induction boilers are also good because they almost never leak, if only the installation of the system is done correctly. The absence of leaks is due to the non-contact method of transferring thermal energy to the heater. The coolant using the technology described above can be heated almost to a vapor state.

This provides sufficient thermal convection to stimulate efficient movement of the coolant through the pipes. In most cases, the heating system will not have to be equipped with a circulation pump, although it all depends on the features and layout of a particular heating system.

Sometimes a circulation pump is needed. Installing the device is relatively easy. Although this will require some skills in the installation of electrical appliances and heating pipes.

But this convenient and reliable device has a number of shortcomings, which should also be considered. For example, the boiler heats not only the coolant, but also the entire workspace surrounding it. It is necessary to allocate a separate room for such a unit and remove all foreign objects from it. For a person, a long stay in the immediate vicinity of a working boiler can also be unsafe.

Induction heaters require electricity to operate. Both homemade and factory-made equipment are connected to a household AC mains.

The device requires electricity to operate. In areas where there is no free access to this benefit of civilization, the induction boiler will be useless. Yes, and where there are frequent power outages, it will demonstrate low efficiency.

An explosion may occur if the instrument is not handled with care.

If the coolant is overheated, it will turn into steam. As a result, the pressure in the system will increase dramatically, which the pipes simply cannot withstand, they will burst. Therefore, for the normal operation of the system, the device should be equipped with at least a pressure gauge, and even better - an emergency shutdown device, a thermostat, etc.

All this can significantly increase the cost of a homemade induction boiler. Although the device is considered to be practically silent, this is not always the case. Some models, for various reasons, may still make some noise. For a self-made device, the likelihood of such an outcome increases.

In the design of both factory-made and home-made induction heaters, there are practically no wearing components. They last a long time and work flawlessly.

Homemade induction boilers

The simplest scheme of the device, which is assembled, consists of a piece of plastic pipe, into the cavity of which various metal elements are laid in order to create a core. It can be a thin stainless wire rolled into balls, chopped into small pieces of wire - wire rod with a diameter of 6-8 mm, or even a drill with a diameter corresponding to the internal size of the pipe. Outside, fiberglass sticks are glued to it, and a wire 1.5-1.7 mm thick is wound on them in glass insulation. The length of the wire is about 11 m. The manufacturing technology can be studied by watching the video:

Then a home-made induction heater was tested by filling it with water and connecting it to a factory-made ORION induction hob with a power of 2 kW instead of a standard inductor. The test results are shown in the following video:

Other masters recommend taking a low-power welding inverter as a source by connecting the terminals of the secondary winding to the coil terminals. If you carefully study the work done by the author, then the following conclusions arise:

• The author did a good job and his product, of course, works.
• No calculations were made for the thickness of the wire, the number and diameter of the turns of the coil. The winding parameters were taken by analogy with the hob, respectively, the induction water heater will turn out to be no higher than 2 kW.
• In the best case, a home-made unit will be able to heat water for two heating radiators of 1 kW each, this is enough to heat one room. In the worst case, the heating will be weak or disappear altogether, because the tests were carried out without a coolant flow.

It is difficult to draw more accurate conclusions due to the lack of information about further tests of the device. Another way to independently organize induction water heating for heating is shown in the following video:

A radiator welded from several metal pipes acts as an external core for eddy currents created by the coil of the same induction hob. The conclusions are as follows:

• The thermal power of the resulting heater does not exceed the electrical power of the panel.
• The number and size of the tubes were chosen at random, but provided sufficient surface for the transfer of heat generated from the eddy currents.
• This scheme of the induction heater proved to be successful for the specific case when the apartment is surrounded by the premises of other heated apartments. In addition, the author did not show the operation of the installation in the cold season with fixing the air temperature in the rooms.

To confirm the conclusions made, it is proposed to watch a video where the author tried to use a similar heater in a separate insulated building:

Operating principle

Induction heating is the heating of materials by electric currents that are induced by an alternating magnetic field. Therefore, this is the heating of products made of conductive materials (conductors) by the magnetic field of inductors (sources of an alternating magnetic field).

Induction heating is carried out as follows. An electrically conductive (metal, graphite) workpiece is placed in the so-called inductor, which is one or more turns of wire (most often copper). Powerful currents of various frequencies (from tens of Hz to several MHz) are induced in the inductor with the help of a special generator, as a result of which an electromagnetic field arises around the inductor. The electromagnetic field induces eddy currents in the workpiece. Eddy currents heat the workpiece under the action of Joule heat.

The inductor-blank system is a coreless transformer in which the inductor is the primary winding. The workpiece is, as it were, a secondary winding, short-circuited. The magnetic flux between the windings closes in air.

At a high frequency, eddy currents are displaced by the magnetic field formed by them into thin surface layers of the workpiece Δ ​​(skin effect), as a result of which their density increases sharply and the workpiece is heated. The underlying layers of the metal are heated due to thermal conductivity. It is not the current that is important, but the high current density. In the skin layer Δ, the current density increases in e times relative to the current density in the workpiece, while 86.4% of the heat from the total heat release is released in the skin layer. The depth of the skin layer depends on the radiation frequency: the higher the frequency, the thinner the skin layer. It also depends on the relative magnetic permeability μ of the workpiece material.

For iron, cobalt, nickel and magnetic alloys at temperatures below the  Curie point, μ has a value from several hundreds to tens of thousands. For other materials (melts, non-ferrous metals, liquid low-melting eutectics, graphite, electrically conductive ceramics, etc.), μ is approximately equal to one.

Formula for calculating skin depth in mm:

Δ=103ρμπf(\displaystyle \Delta =10^(3)(\sqrt (\frac (\rho )(\mu \pi f)))),

where ρ - specific electrical resistance of the workpiece material at the processing temperature, Ohm m, f- frequency of the electromagnetic field generated by the inductor, Hz.

For example, at a frequency of 2 MHz, the skin depth for copper is about 0.047 mm, for iron ≈ 0.0001 mm.

The inductor gets very hot during operation, as it absorbs its own radiation. In addition, it absorbs heat radiation from a hot workpiece. They make inductors from copper tubes cooled by water. Water is supplied by suction - this ensures safety in case of a burn or other depressurization of the inductor.

Operating principle

The melting unit of the induction furnace is used to heat a wide variety of metals and alloys. The classic design consists of the following elements:

1. Drain pump.
2. Water cooled inductor.
3. Frame in stainless steel or aluminium.
4. Contact area.
5. Hearth made of heat-resistant concrete.
6. Support with hydraulic cylinder and bearing assembly.

The principle of operation is based on the creation of eddy induced Foucault currents. As a rule, during the operation of household appliances, such currents cause failures, but in this case they are used to heat the charge to the required temperature. Almost all electronics start to heat up during operation. This negative factor in the use of electricity is used to its full potential.

Device advantages

The induction melting furnace has been used relatively recently. Famous open-hearth furnaces, blast furnaces and other types of equipment are installed at production sites. Such a metal melting furnace has the following advantages:

1. The application of the principle of induction allows you to make the equipment compact. That is why there are no problems with their placement in small rooms. An example is blast furnaces, which can only be installed in prepared premises.
2. The results of the conducted studies indicate that the efficiency is almost 100%.
3. High melting speed. The high efficiency index determines that it takes much less time to heat up the metal when compared with other furnaces.
4. Some furnaces during melting can lead to a change in the chemical composition of the metal. Induction takes first place in terms of melt purity. The generated Foucault currents heat the workpiece from the inside, which eliminates the possibility of getting into the composition of various impurities.

It is the latter advantage that determines the spread of the induction furnace in jewelry, since even a small concentration of foreign impurities can adversely affect the result.

Due to the fact that M. Faraday discovered the phenomenon of electromagnetic induction back in 1831, the world saw a large number of devices that heat water and other media.

Because this discovery was realized, people use it daily in everyday life:

• Electric kettle with disc heater for water heating;
• Multicooker oven;
• induction hob;
• Microwaves (stove);
• Heater;
• Heating column.

Also, the opening is applied to the extruder (not mechanical). Previously, it was widely used in metallurgy and other industries related to metal processing. The factory inductive boiler operates on the principle of the action of eddy currents on a special core located in the inside of the coil. Foucault eddy currents are superficial, so it is better to take a hollow metal pipe as a core, through which the coolant element passes.

The occurrence of electric currents occurs due to the supply of an alternating voltage to the winding, causing the appearance of an alternating electric magnetic field, which changes the potentials 50 times / sec. at standard industrial frequency of 50 Hz.

At the same time, the Ruhmkorff induction coil is designed in such a way that it can be connected directly to the AC mains. In production, high-frequency electric currents are used for such heating - up to 1 MHz, so it is rather difficult to achieve the operation of the device at 50 Hz. The thickness of the wire and the number of winding turns used by the device are calculated separately for each unit according to a special method for the required heat output. A home-made, powerful unit must function efficiently, quickly heat the water flowing through the pipe and not heat up.

Organizations invest heavily in the development and implementation of such products, so:

• All tasks are solved successfully;
• The efficiency of the heating device is 98%;
• Functions without interruption.

In addition to the highest efficiency, one cannot but attract the speed with which the heating of the medium passing through the core takes place. On fig. a scheme of functioning of an induction water heater created at the plant is proposed. Such a scheme has a VIN brand unit, which is produced by the Izhevsk plant.

How long the unit will work depends solely on how tight the case is and the insulation of the turns of the wire is not damaged, and this is a rather significant period, according to the manufacturer - up to 30 years.

For all these advantages, which the device has 100%, you need to pay a lot of money, an inductor, magnetic water heater is the most expensive of all types of heating installations. Therefore, many craftsmen prefer to assemble an ultra-economical unit for heating on their own.

Rules for the manufacture of equipment independently

In order for the induction heating installation to work correctly, the current for such a product must correspond to the power (it must be at least 15 amperes, if required, it can be more).

• The wire should be cut into pieces no more than five centimeters. This is necessary for efficient heating in a high-frequency field.
• The body must be no smaller in diameter than the prepared wire, and have thick walls.
• For attachment to the heating network, a special adapter is attached to one side of the structure.
• A net should be placed at the bottom of the pipe to prevent the wire from falling out.
• The latter is needed in such quantity that it fills the entire internal space.
• The design is closed, an adapter is placed.
• Then a coil is constructed from this pipe. To do this, wrap it with already prepared wire. The number of turns must be observed: minimum 80, maximum 90.
• After connecting to the heating system, water is poured into the apparatus. The coil is connected to the prepared inverter.
• A water pump is installed.
• The temperature controller is installed.

Thus, the calculation of induction heating will depend on the following parameters: length, diameter, temperature and processing time

Pay attention to the inductance of the tires leading to the inductor, which can be much higher than the inductor itself.

High precision induction heating

Such heating has the simplest principle, since it is non-contact. High-frequency pulsed heating makes it possible to achieve the highest temperature conditions, at which it is possible to process the most difficult metals in melting. To perform induction heating, it is necessary to create the required voltage of 12V (volts) and the frequency of the inductance in electromagnetic fields.

This can be done in a special device - an inductor. It is powered by electricity from an industrial power supply at 50 Hz.

It is possible to use individual power supplies for this - converters / generators. The simplest device for a low-frequency device is a spiral (insulated conductor), which can be placed in the inside of a metal pipe or wound around it. The going currents heat the tube, which, in the future, gives heat to the living room.

The use of induction heating at minimum frequencies is not a frequent occurrence. The most common processing of metals at a higher or medium frequency. Such devices are distinguished by the fact that the magnetic wave goes to the surface, where it decays. Energy is converted into heat. For the effect to be better, both components must have a similar shape. Where is heat applied?

Today, the use of high-frequency heating is widespread:

• For melting metals, and their soldering by a non-contact method;
• Engineering industry;
• Jewelry business;
• Creation of small elements (boards) that can be damaged when using other techniques;
• Hardening of surfaces of parts, different configurations;
• Heat treatment of parts;
• Medical practice (disinfection of devices/instruments).

Heating can solve many problems.

What is induction heating

How an induction water heater works.

The induction device works on the energy generated by the electromagnetic field. It is absorbed by the heat carrier, then giving it to the premises:

1. An inductor creates an electromagnetic field in such a water heater. This is a multi-turn cylindrical wire coil.
2. Flowing through it, an alternating electric current around the coil generates a magnetic field.
3. Its lines are placed perpendicular to the electromagnetic flux vector. When moved, they recreate a closed circle.
4. The eddy currents created by alternating current convert the energy of electricity into heat.

Thermal energy during induction heating is spent sparingly and at a low heating rate. Thanks to this, the induction device brings the water for the heating system to a high temperature in a short time period.

Device features

The electric current is connected to the primary winding.

Induction heating is carried out using a transformer. It consists of a pair of windings:

• external (primary);
• short-circuited internal (secondary).

Eddy currents occur in the deep part of the transformer. They redirect the emerging electromagnetic field to the secondary circuit. He simultaneously performs the function of the body and acts as a heating element for water.

With an increase in the density of vortex flows directed to the core, it first heats up itself, then the entire thermal element.

To supply cool water and remove the prepared coolant to the heating system, the induction heater is equipped with a pair of pipes:

1. The lower one is installed on the inlet of the water supply.
2. The upper branch pipe - to the supply section of the heating system.

What elements does the device consist of, and how does it work

The induction water heater consists of the following structural elements:

A photo	Structural node
	Inductor. It consists of many coils of copper wire. They generate an electromagnetic field.
	A heating element. This is a pipe made of metal or steel wire trimmings placed inside the inductor.
	Generator. It transforms household electricity into high-frequency electric current. The role of the generator can be played by an inverter from the welding machine.

The scheme of operation of the heating system with an induction water heater.

When all components of the device interact, heat energy is generated and transferred to water. The scheme of operation of the unit is as follows:

1. The generator produces a high-frequency electric current. He then passes it on to an induction coil.
2. She, having perceived the current, transforms it into an electric magnetic field.
3. The heater, located inside the coil, is heated by the action of vortex flows that appear due to a change in the magnetic field vector.
4. The water circulating inside the element is heated by it. Then it enters the heating system.

Advantages and disadvantages of the induction heating method

The unit is compact and takes up little space.

Induction heaters are endowed with such advantages:

• high level of efficiency;
• do not need frequent maintenance;
• they take up little free space;
• due to vibrations of the magnetic field, scale does not settle inside them;
• devices are silent;
• they are safe;
• due to the tightness of the housing, there are no leaks;
• the operation of the heater is fully automated;
• the unit is environmentally friendly, does not emit soot, soot, carbon monoxide, etc.

In the photo - a factory water-heating induction boiler.

The main disadvantage of the device is the high cost of its factory models..

However, this disadvantage can be leveled if you assemble an induction heater with your own hands. The unit is mounted from easily accessible elements, their price is low.

Benefits of using all types of induction heaters

The induction heater has undoubted advantages and is the leader among all types of devices. This advantage consists of the following:

• It consumes less electricity and does not pollute the environment.
• Easy to operate, it provides high quality work and allows you to control the process.
• Heating through the walls of the chamber provides a special purity and the ability to obtain ultra-pure alloys, while melting can be carried out in different atmospheres, including inert gases and in vacuum.
• With its help uniform heating of details of any form or selective heating is possible.
• Finally, induction heaters are universal, which allows them to be used everywhere, replacing outdated energy-consuming and inefficient installations.

When making an induction heater with your own hands, you need to worry about the safety of the device. To do this, it is necessary to be guided by the following rules that increase the level of reliability of the overall system:

1. A safety valve should be inserted into the upper tee to relieve excess pressure. Otherwise, if the circulation pump fails, the core will simply burst under the influence of steam. As a rule, the scheme of a simple induction heater provides for such moments.
2. The inverter is connected to the network only through the RCD. This device works in critical situations and will help to avoid a short circuit.
3. The welding inverter must be grounded by leading the cable to a special metal circuit mounted in the ground behind the walls of the structure.
4. The body of the induction heater must be placed at a height of 80 cm above the floor. Moreover, the distance to the ceiling should be at least 70 cm, and to other pieces of furniture - more than 30 cm.
5. An induction heater is a source of a very strong electromagnetic field, so this installation should be kept away from living quarters and enclosures with pets.

Diagram of an induction heater

Thanks to the discovery by M. Faraday in 1831 of the phenomenon of electromagnetic induction, many devices have appeared in our modern life that heat water and other media. Every day we use an electric kettle with a disc heater, a multicooker, an induction hob, since it was only in our time that we managed to realize this discovery for everyday life. Previously, it was used in the metallurgical and other branches of the metalworking industry.

The factory induction boiler uses in its work the principle of the action of eddy currents on a metal core placed inside the coil. Foucault eddy currents are of a surface nature, so it makes sense to use a hollow metal pipe as a core, through which a heated coolant flows.

The principle of operation of the induction heater

The occurrence of currents is due to the supply of an alternating electrical voltage to the winding, causing the appearance of an alternating electromagnetic field that changes potentials 50 times per second at a normal industrial frequency of 50 Hz. At the same time, the induction coil is designed in such a way that it can be connected directly to the AC mains. In industry, high-frequency currents are used for such heating - up to 1 MHz, so it is not easy to achieve device operation at a frequency of 50 Hz.

The thickness of the copper wire and the number of winding turns used by induction water heaters are calculated separately for each unit using a special method for the required heat output. The product must work efficiently, quickly heat the water flowing through the pipe and at the same time not overheat. Enterprises invest a lot of money in the development and implementation of such products, so all tasks are solved successfully, and the heater efficiency indicator is 98%.

In addition to high efficiency, the speed at which the medium flowing through the core is heated is especially attractive. The figure shows a diagram of the operation of an induction heater made in the factory. Such a scheme is used in units of the well-known trademark "VIN", produced by the Izhevsk plant.

Heater operation diagram

The durability of the heat generator depends only on the tightness of the case and the integrity of the insulation of the turns of the wire, and this turns out to be a rather long period, the manufacturers declare - up to 30 years. For all these advantages that these devices actually possess, you have to pay a lot of money, an induction water heater is the most expensive of all types of heating electrical installations. For this reason, some craftsmen took up the manufacture of a home-made device in order to use it in heating the house.

DIY manufacturing process

The following tools will be useful for work:

• welding inverter;
• welding generating current with a power of 15 amperes.

You will also need copper wire, which is wound around the core body. The device will act as an inductor. The wire contacts are connected to the inverter terminals so that no twists are formed. The piece of material needed to assemble the core must be the correct length. On average, the number of turns is 50, the diameter of the wire is 3 millimeters.

Copper wire of different diameters for winding

Now let's move on to the core. In his role will be a polymer pipe made of polyethylene. This type of plastic can withstand quite high temperatures. Core diameter - 50 millimeters, wall thickness - at least 3 mm. This part is used as a gauge on which a copper wire is wound, forming an inductor. Almost anyone can assemble the simplest induction water heater.

On the video you will see a way - how to independently organize induction heating of water for heating:

First option

The wire is cut into 50 mm segments, a plastic tube is filled with it. To prevent it from spilling out of the pipe, plug the ends with wire mesh. At the ends, adapters are placed from the pipe, in the place where the heater is connected.

A winding is wound on the body of the latter with copper wire. For this purpose, you need about 17 meters of wire: you need to make 90 turns, the pipe diameter is 60 millimeters. 3.14×60×90=17 m.

It's important to know! When checking the operation of the device, make sure that there is water (coolant) in it. Otherwise, the body of the device will quickly melt.
. The pipe crashes into the pipeline

The heater is connected to the inverter. It remains to fill the device with water and turn it on. Everything is ready!

The pipe crashes into the pipeline. The heater is connected to the inverter. It remains to fill the device with water and turn it on. Everything is ready!

Second option

This option is much easier. A straight section of a meter size is selected on the vertical part of the pipe. It should be carefully cleaned of paint using sandpaper. Further, this section of the pipe is covered with three layers of electrical fabric. An induction coil is wound with copper wire. The entire connection system is well insulated. Now you can connect the welding inverter and the assembly process is complete.

Induction coil wrapped with copper wire

Before you start making a water heater with your own hands, it is advisable to familiarize yourself with the characteristics of factory products and study their drawings. This will help to understand the initial data of home-made equipment and avoid possible errors.

Third option

To make the heater in this more complicated way, you need to use welding. To work, you still need a three-phase transformer. Two pipes must be welded into each other, which will act as a heater and a core. A winding is wound onto the body of the inductor. This increases the performance of the device, which has a compact size, which is very convenient for its use at home.

Winding on the body of the inductor

For water supply and drainage, 2 branch pipes are welded into the body of the inductor. In order not to lose heat and prevent possible current leakage, insulation must be made. It will eliminate the problems described above, and completely eliminate the appearance of noise during the operation of the boiler.

Depending on the design features, floor and desktop induction furnaces are distinguished. Regardless of which option was chosen, there are several basic rules for installation:

1. When the equipment is in operation, the power grid is subjected to a high load. In order to exclude the possibility of a short circuit due to wear of the insulation, high-quality grounding must be carried out during installation.
2. The design has a water cooling circuit, which eliminates the possibility of overheating of the main elements. That is why it is necessary to ensure a reliable rise in water.
3. If a desktop oven is being installed, then attention should be paid to the stability of the base used.
4. The metal melting furnace is a complex electrical appliance, the installation of which must follow all the manufacturer's recommendations. Particular attention is paid to the parameters of the power source, which must match the model of the device.
5. Do not forget that there should be quite a lot of free space around the stove. During operation, even a small melt in terms of volume and mass can accidentally splash out of the mold. At temperatures above 1000 degrees Celsius, it will cause irreparable damage to various materials, and may also cause a fire.

The device may become very hot during operation. That is why there should not be any flammable or explosive substances nearby. In addition, according to fire safety regulations, nearby should be installed fire shield.

Safety regulations

for heating systems that use induction heating, it is important to follow a few rules to avoid leaks, loss of efficiency, energy consumption, accidents. . Induction heating systems require a safety valve to release water and steam in case the pump fails.


To prevent failures in the operation of the electrical network, it is recommended to connect a do-it-yourself boiler with induction heating according to the proposed schemes to a separate supply line, the cable cross section of which will be at least 5 mm2

Ordinary wiring may not be able to withstand the required power consumption.

1. Induction heating systems require a safety valve to release water and steam in case the pump fails.
2. A manometer and an RCD are required for the safe operation of a do-it-yourself heating system.
3. The presence of grounding and electrical insulation of the entire induction heating system will prevent electric shock.
4. In order to avoid the harmful effects of the electromagnetic field on the human body, it is better to take such systems outside the residential area, where installation rules should be observed, according to which the induction heating device should be placed at a distance of 80 cm from horizontal (floor and ceiling) and 30 cm from vertical surfaces.
5. Before turning on the system, be sure to check the presence of the coolant.
6. To prevent malfunctions in the electrical network, it is recommended to connect a do-it-yourself induction heating boiler according to the proposed schemes to a separate supply line, the cable cross section of which will be at least 5 mm2. Ordinary wiring may not be able to withstand the required power consumption.

Creating sophisticated fixtures

It is more difficult to make an HDTV heating installation with your own hands, but it is subject to radio amateurs, because to collect it you will need a multivibrator circuit. The principle of operation is similar - eddy currents arising from the interaction of the metal filler in the center of the coil and its own highly magnetic field heat the surface.

Design of HDTV installations

Since even small coils produce a current of about 100 A, a resonating capacitance will need to be connected with them to balance the induction thrust. There are 2 types of working circuits for heating HDTV at 12 V:

• connected to mains power.

• targeted electrical;
• connected to mains power.

In the first case, a mini HDTV installation can be assembled in an hour. Even in the absence of a 220 V network, you can use such a generator anywhere, but if you have car batteries as power sources. Of course, it is not powerful enough to melt metal, but it is able to heat up to the high temperatures needed for fine work, such as heating knives and screwdrivers to blue. To create it, you need to purchase:

• field effect transistors BUZ11, IRFP460, IRFP240;
• car battery from 70 A / h;
• high voltage capacitors.

The current of the 11 A power supply is reduced to 6 A during the heating process due to the resistance of the metal, but the need for thick wires that can withstand a current of 11-12 A remains to avoid overheating.

The second circuit for an induction heating installation in a plastic case is more complex, based on the IR2153 driver, but it is more convenient to build a 100k resonance over the regulator using it. It is necessary to control the circuit through a network adapter with a voltage of 12 V or more. The power unit can be connected directly to the main network of 220 V using a diode bridge. The resonance frequency is 30 kHz. The following items will be required:

• ferrite core 10 mm and choke 20 turns;
• copper tube as an HDTV coil of 25 turns per mandrel 5–8 cm;
• capacitors 250 V.

Vortex heaters

A more powerful installation, capable of heating the bolts to yellow, can be assembled according to a simple scheme. But during operation, the heat generation will be quite large, so it is recommended to install radiators on transistors. You will also need a choke, which you can borrow from the power supply of any computer, and the following auxiliary materials:

• steel ferromagnetic wire;
• copper wire 1.5 mm;
• field-effect transistors and diodes for reverse voltage from 500 V;
• zener diodes with a power of 2-3 W with a calculation of 15 V;
• simple resistors.

Depending on the desired result, the winding of the wire on the copper base is from 10 to 30 turns. Next comes the assembly of the circuit and the preparation of the base coil of the heater from about 7 turns of 1.5 mm copper wire. It connects to the circuit and then to electricity.

Craftsmen familiar with welding and operating a three-phase transformer can further increase the efficiency of the device while reducing weight and size. To do this, it is necessary to weld the bases of two pipes, which will serve as both a core and a heater, and after winding, weld two pipes into the body to supply and remove the coolant.

Advantages and disadvantages

Having dealt with the principle of operation of the induction heater, you can consider its positive and negative sides. Given the high popularity of this type of heat generators, it can be assumed that it has much more advantages than disadvantages. Among the most significant advantages are:

• Simplicity of design.
• High rate of efficiency.
• Long service life.
• Small risk of damage to the device.
• Significant energy savings.

Since the performance indicator of an induction boiler is in a wide range, it is possible to choose a unit for a specific building heating system without any problems. These devices are able to quickly heat the coolant to a predetermined temperature, which has made them a worthy competitor to traditional boilers.

During operation of the induction heater, a slight vibration is observed, due to which scale is shaken off the pipes. As a result, the unit can be cleaned less frequently. Since the coolant is in constant contact with the heating element, the risks of its failure are relatively small.

Part 1. DIY INDUCTION BOILER - it's easy. Attachment for induction hob.

If no mistakes were made during the installation of the induction boiler, then leakage is practically excluded. This is due to the contactless transfer of heat energy to the heater. Using induction water heating technology allows you to bring it almost to a gaseous state. Thus, an efficient movement of water through the pipes is achieved, and in some situations it is even possible to dispense with the use of circulation pumping units.

Unfortunately, ideal devices do not exist today. Along with a large number of advantages, induction heaters also have a number of disadvantages. Since the unit requires electricity to operate, it will not be able to operate at maximum efficiency in regions with frequent power outages. When the coolant overheats, the pressure in the system increases sharply and the pipes can break. To avoid this, the induction heater must be equipped with an emergency shutdown device.

DIY induction heater

Working principle of induction heating

The operation of an induction heater uses the energy of an electromagnetic field, which the heated object absorbs and converts into heat. To generate a magnetic field, an inductor is used, that is, a multi-turn cylindrical coil. Passing through this inductor, an alternating electric current creates an alternating magnetic field around the coil.

A homemade inverter heater allows you to heat up quickly and to very high temperatures. With the help of such devices, you can not only heat water, but even melt various metals.

If a heated object is placed inside or near the inductor, it will be pierced by the flux of the magnetic induction vector, which is constantly changing in time. In this case, an electric field arises, the lines of which are located perpendicular to the direction of the magnetic flux and move in a vicious circle. Thanks to these vortex flows, electrical energy is transformed into thermal energy and the object heats up.

Thus, the electrical energy of the inductor is transferred to the object without the use of contacts, as happens in resistance furnaces. As a result, thermal energy is spent more efficiently, and the heating rate increases markedly. This principle is widely used in the field of metal processing: its melting, forging, brazing, etc. With no less success, a vortex induction heater can be used to heat water.

High frequency induction heaters

The widest range of applications is for high-frequency induction heaters. The heaters are characterized by a high frequency of 30-100 kHz and a wide power range of 15-160 kW. The high-frequency type provides a small depth of heating, but this is enough to improve the chemical properties of the metal.

High frequency induction heaters are easy to operate and economical, while their efficiency can reach 95%. All types work continuously for a long time, and the two-block version (when the high-frequency transformer is placed in a separate block) allows round-the-clock operation. The heater has 28 types of protections, each of which is responsible for its own function. Example: control of water pressure in the cooling system.

• Induction heater 60 kW Perm
• Induction heater 65 kW Novosibirsk
• Induction heater 60 kW Krasnoyarsk
• Induction heater 60 kW Kaluga
• Induction heater 100 kW Novosibirsk
• Induction heater 120 kW Yekaterinburg
• Induction heater 160 kW Samara

Application:

• surface hardened gear
• shaft hardening
• crane wheel hardening
• heating parts before bending
• soldering of cutters, cutters, drill bits
• heating the workpiece during hot stamping
• bolt landing
• welding and surfacing of metals
• restoration of details.

Induction furnaces are used for smelting metals and are distinguished by the fact that they are heated by means of electric current. The excitation of the current occurs in the inductor, or rather in a non-variable field.

In such constructions, energy is converted several times (in this sequence):

• into the electromagnetic
• electrical;
• thermal.

Such stoves allow you to use heat with maximum efficiency, which is not surprising, because they are the most advanced of all existing models that run on electricity.

Note! Induction designs are of two types - with or without a core. In the first case, the metal is placed in a tubular chute, which is located around the inductor. The core is located in the inductor itself. The second option is called the crucible, because in it the metal with the crucible is already inside the indicator. Of course, there can be no talk of any core in this case.

In today's article we will talk about how to makeDIY induction oven.

Among the many benefits are the following:

• environmental cleanliness and safety;
• increased homogeneity of the melt due to the active movement of the metal;
• speed - the oven can be used almost immediately after switching on;
• zone and focused orientation of energy;
• high melting rate;
• lack of waste from alloying substances;
• the ability to adjust the temperature;
• numerous technical possibilities.

But there are also disadvantages.

1. The slag is heated by the metal, as a result of which it has a low temperature.
2. If the slag is cold, then it is very difficult to remove phosphorus and sulfur from the metal.
3. Between the coil and the melting metal, the magnetic field dissipates, so a reduction in lining thickness will be required. This will soon lead to the fact that the lining itself will fail.

Video - Induction furnace

Industrial Application

Both design options are used in the smelting of iron, aluminium, steel, magnesium, copper and precious metals. The useful volume of such structures can range from several kilograms to several hundred tons.

Furnaces for industrial use are divided into several types.

1. Medium frequency designs are commonly used in mechanical engineering and metallurgy. With their help, steel is melted, and when using graphite crucibles, non-ferrous metals are also melted.
2. Industrial frequency designs are used in iron smelting.
3. Resistance structures are intended for melting aluminum, aluminum alloys, zinc.

Note! It was induction technology that formed the basis of more popular devices - microwave ovens.

domestic use

For obvious reasons, the induction melting furnace is rarely used in the home. But the technology described in the article is found in almost all modern houses and apartments. These are the microwaves mentioned above, and induction cookers, and electric ovens.

Consider, for example, plates. They heat the dishes due to inductive eddy currents, as a result of which the heating occurs almost instantly. It is characteristic that it is impossible to turn on the burner on which there are no dishes.

The efficiency of induction cookers reaches 90%. For comparison: for electric stoves it is about 55-65%, and for gas stoves - no more than 30-50%. But in fairness, it is worth noting that the operation of the described stoves requires special dishes.

Homemade induction oven

Not so long ago, domestic radio amateurs clearly demonstrated that you can make an induction furnace yourself. Today, there are a lot of different schemes and manufacturing technologies, but we have given only the most popular of them, which means the most effective and easy to implement.

Induction furnace from high frequency generator

Below is an electrical circuit for making a homemade device from a high-frequency (27.22 megahertz) generator.

In addition to the generator, the assembly will require four high-power light bulbs and a heavy lamp for the ready-to-work indicator.

Note! The main difference between the furnace, made according to this scheme, is the condenser handle - in this case, it is located outside.

In addition, the metal in the coil (inductor) will melt in the device of the smallest power.

When manufacturing, it is necessary to remember some important points that affect the speed of metal boarding. This:

• power;
• frequency;
• eddy losses;
• heat transfer intensity;
• hysteresis loss.

The device will be powered by a standard 220 V network, but with a pre-installed rectifier. If the furnace is intended for heating a room, then it is recommended to use a nichrome spiral, and if for melting, then graphite brushes. Let's get acquainted with each of the structures in more detail.

Video - Welding inverter design

The essence of the design is as follows: a pair of graphite brushes is installed, and powdered granite is poured between them, after which a step-down transformer is connected. It is characteristic that when smelting, one can not be afraid of electric shock, since there is no need to use 220 V.

Assembly technology

Step 1. The base is assembled - a box of fireclay bricks measuring 10x10x18 cm, laid on a refractory tile.

Step 2. Boxing is finished with asbestos cardboard. After wetting with water, the material softens, which allows you to give it any shape. If desired, the structure can be wrapped with steel wire.

Note! The dimensions of the box may vary depending on the power of the transformer.

Step 3. The best option for a graphite furnace is a transformer from a 0.63 kW welding machine. If the transformer is designed for 380 V, then it can be rewound, although many experienced electricians say that you can leave everything as it is.

Step 4. The transformer is wrapped with thin aluminum - so the structure will not get very hot during operation.

Step 5. Graphite brushes are installed, a clay substrate is installed on the bottom of the box - so the molten metal will not spread.

The main advantage of such a furnace is the high temperature, which is suitable even for melting platinum or palladium. But among the minuses is the rapid heating of the transformer, a small volume (no more than 10 g can be smelted at a time). For this reason, a different design will be required for melting large volumes.

So, for the smelting of large volumes of metal, a furnace with nichrome wire is required. The principle of operation of the design is quite simple: an electric current is applied to a nichrome spiral, which heats up and melts the metal. There are a lot of different formulas on the Web for calculating the length of the wire, but they are all, in principle, the same.

Step 1. For the spiral, nichrome ø0.3 mm is used, about 11 m long.

Step 2. The wire must be wound. To do this, you need a straight copper tube ø5 mm - a spiral is wound on it.

Step 3. A small ceramic pipe ø1.6 cm and 15 cm long is used as a crucible. One end of the pipe is plugged with asbestos thread - so the molten metal will not flow out.

Step 4. After checking the performance and the spiral is laid around the pipe. At the same time, the same asbestos thread is placed between the turns - it will prevent a short circuit and limit the access of oxygen.

Step 5. The finished coil is placed in a cartridge from a high power lamp. Such cartridges are usually ceramic and have the required size.

The advantages of such a design:

• high productivity (up to 30 g per run);
• fast heating (about five minutes) and long cooling;
• ease of use - it is convenient to pour metal into molds;
• prompt replacement of the spiral in case of burnout.

But there are, of course, downsides:

• nichrome burns out, especially if the spiral is poorly insulated;
• insecurity - the device is connected to the mains 220 V.

Note! You can not add metal to the stove if the previous portion is already melted there. Otherwise, all the material will scatter around the room, moreover, it may injure the eyes.

As a conclusion

As you can see, you can still make an induction furnace on your own. But to be frank, the described design (like everything available on the Internet) is not quite a furnace, but a Kukhtetsky laboratory inverter. It is simply impossible to assemble a full-fledged induction structure at home.

Heating and melting of metals in induction furnaces occur due to internal heating and changes in the crystalline ...

How to assemble an induction furnace for melting metal at home with your own hands

Melting metal by induction is widely used in various industries: metallurgy, engineering, jewelry. A simple induction type furnace for melting metal at home can be assembled with your own hands.

Operating principle

Heating and melting of metals in induction furnaces occur due to internal heating and changes in the crystal lattice of the metal when high-frequency eddy currents pass through them. This process is based on the phenomenon of resonance, in which eddy currents have a maximum value.

To cause the flow of eddy currents through the melted metal, it is placed in the zone of action of the electromagnetic field of the inductor - the coil. It can be in the form of a spiral, figure eight or trefoil. The shape of the inductor depends on the size and shape of the heated workpiece.

The inductor coil is connected to an alternating current source. In industrial melting furnaces, industrial frequency currents of 50 Hz are used; for melting small volumes of metals in jewelry, high-frequency generators are used, as they are more efficient.

Kinds

Eddy currents are closed along a circuit limited by the magnetic field of the inductor. Therefore, heating of conductive elements is possible both inside the coil and from its outer side.

Therefore, induction furnaces are of two types:
• channel, in which the channels located around the inductor are the container for melting metals, and the core is located inside it;
• crucible, they use a special container - a crucible made of heat-resistant material, usually removable.

channel furnace too overall and designed for industrial volumes of metal melting. It is used in the smelting of cast iron, aluminum and other non-ferrous metals.

crucible furnace quite compact, it is used by jewelers, radio amateurs, such an oven can be assembled with your own hands and used at home.

Device

A home-made furnace for melting metals has a fairly simple design and consists of three main blocks placed in a common housing:
• high frequency alternator;
• inductor - do-it-yourself spiral winding of copper wire or tube;
• crucible.

The crucible is placed in an inductor, the ends of the winding are connected to a current source. When current flows through the winding, an electromagnetic field with a variable vector arises around it. In a magnetic field, eddy currents arise, directed perpendicular to its vector and passing through a closed loop inside the winding. They pass through the metal placed in the crucible, while heating it to the melting point.

Advantages of the induction furnace:

• fast and uniform heating of the metal immediately after switching on the installation;
• directivity of heating - only the metal is heated, and not the entire installation;
• high melting rate and homogeneity of the melt;
• there is no evaporation of the alloying components of the metal;
• the installation is environmentally friendly and safe.

A welding inverter can be used as a generator of an induction furnace for melting metal. You can also assemble the generator according to the diagrams below with your own hands.

Furnace for melting metal on a welding inverter

This design is simple and safe as all inverters are equipped with internal overload protection. The entire assembly of the furnace in this case comes down to making an inductor with your own hands.

It is usually performed in the form of a spiral from a copper thin-walled tube with a diameter of 8-10 mm. It is bent according to a template of the desired diameter, placing the turns at a distance of 5-8 mm. The number of turns is from 7 to 12, depending on the diameter and characteristics of the inverter. The total resistance of the inductor must be such that it does not cause an overcurrent in the inverter, otherwise it will be tripped by the internal protection.

The inductor can be mounted in a housing made of graphite or textolite and a crucible can be installed inside. You can simply put the inductor on a heat-resistant surface. The housing must not conduct current, otherwise the eddy current circuit will pass through it and the power of the installation will be reduced. For the same reason, it is not recommended to place foreign objects in the melting zone.

When working from a welding inverter, its housing must be grounded! The socket and wiring must be rated for the current drawn by the inverter.

The heating system of a private house is based on the operation of a furnace or boiler, the high performance and long uninterrupted service life of which depends both on the brand and installation of the heating devices themselves, and on the correct installation of the chimney.

Transistor induction furnace: circuit

There are many different ways to assemble an induction heater with your own hands. A fairly simple and proven scheme of a furnace for melting metal is shown in the figure:

To assemble the installation with your own hands, you will need the following parts and materials:
• two field-effect transistors of the IRFZ44V type;
• two diodes UF4007 (you can also use UF4001);
• resistor 470 Ohm, 1 W (you can take two series-connected 0.5 W each);
• film capacitors for 250 V: 3 pieces with a capacity of 1 microfarad; 4 pieces - 220 nF; 1 piece - 470 nF; 1 piece - 330 nF;
• copper winding wire in enamel insulation Ø1.2 mm;
• copper winding wire in enamel insulation Ø2 mm;
• two rings from chokes taken from a computer power supply.

Do-it-yourself assembly sequence:

• Field-effect transistors are mounted on radiators. Since the circuit gets very hot during operation, the radiator must be large enough. You can also install them on one radiator, but then you need to isolate the transistors from the metal using gaskets and washers made of rubber and plastic. The pinout of field effect transistors is shown in the figure.

• It is necessary to make two chokes. For their manufacture, copper wire with a diameter of 1.2 mm is wound around rings taken from the power supply of any computer. These rings are made of powdered ferromagnetic iron. They need to be wound from 7 to 15 turns of wire, trying to maintain the distance between the turns.

• The capacitors listed above are assembled into a battery with a total capacity of 4.7 microfarads. Connection of capacitors - parallel.

• The inductor winding is made of copper wire with a diameter of 2 mm. 7-8 turns of winding are wound on a cylindrical object suitable for the diameter of the crucible, leaving long enough ends to connect to the circuit.
• Connect the elements on the board in accordance with the diagram. A 12 V, 7.2 A/h battery is used as a power source. The current consumed in operation is about 10 A, the battery capacity in this case is enough for about 40 minutes. If necessary, the furnace body is made of heat-resistant material, for example, textolite. The power of the device can be changed by changing the number of turns of the inductor winding and their diameter.

During prolonged operation, the heater elements may overheat! You can use a fan to cool them.

Induction heater for melting metal: video

Lamp induction oven

A more powerful induction furnace for melting metals can be assembled by hand on vacuum tubes. The diagram of the device is shown in the figure.

To generate high-frequency current, 4 beam lamps connected in parallel are used. A copper tube with a diameter of 10 mm is used as an inductor. The unit is equipped with a trimmer capacitor for power adjustment. The output frequency is 27.12 MHz.

To assemble the circuit you need:

• 4 vacuum tubes - tetrodes, you can use 6L6, 6P3 or G807;
• 4 chokes for 100 ... 1000 μH;
• 4 capacitors at 0.01 uF;
• neon indicator lamp;
• tuning capacitor.

Assembling the device with your own hands:

1. An inductor is made from a copper tube, bending it in the form of a spiral. The diameter of the turns is 8-15 cm, the distance between the turns is at least 5 mm. The ends are tinned for soldering to the circuit. The diameter of the inductor must be 10 mm larger than the diameter of the crucible placed inside.
2. Place the inductor in the housing. It can be made from a heat-resistant non-conductive material, or from metal, providing thermal and electrical insulation from the circuit elements.
3. Cascades of lamps are assembled according to the scheme with capacitors and chokes. Cascades are connected in parallel.
4. Connect a neon indicator lamp - it will signal the readiness of the circuit for operation. The lamp is brought to the installation housing.
5. A tuning capacitor of variable capacitance is included in the circuit, its handle is also displayed on the case.

For all lovers of cold-smoked delicacies, we suggest you find out here how to quickly and easily make a smokehouse with your own hands, and here you can get acquainted with the photo and video instructions for making a cold-smoked smoke generator.

Circuit cooling

Industrial melting plants are equipped with a forced cooling system using water or antifreeze. Water cooling at home will require additional costs, comparable in price to the cost of the metal melting plant itself.

Air-cooling with a fan is possible provided that the fan is sufficiently remote. Otherwise, the metal winding and other elements of the fan will serve as an additional circuit for closing eddy currents, which will reduce the efficiency of the installation.

Elements of the electronic and lamp circuits are also able to actively heat up. For their cooling, heat-removing radiators are provided.

Work Safety Measures

• The main danger when working with a home-made installation is the risk of burns from the heated elements of the installation and molten metal.
• The lamp circuit includes elements with high voltage, so it must be placed in a closed case, eliminating accidental contact with the elements.
• The electromagnetic field can affect objects that are outside the device case. Therefore, before work, it is better to put on clothes without metal elements, remove complex devices from the coverage area: phones, digital cameras.

A domestic metal melting furnace can also be used to quickly heat up metal elements, for example, when they are tinned or shaped. The characteristics of the presented installations can be adjusted to a specific task by changing the parameters of the inductor and the output signal of the generator sets - this way you can achieve their maximum efficiency.

Induction furnaces are used for smelting metals and are distinguished by the fact that they are heated by means of electric current. The excitation of the current occurs in the inductor, or rather in a non-variable field.

In such constructions, energy is converted several times (in this sequence):

• into the electromagnetic
• electrical;
• thermal.

Such stoves allow you to use heat with maximum efficiency, which is not surprising, because they are the most advanced of all existing models that run on electricity.

Note! Induction designs are of two types - with or without a core. In the first case, the metal is placed in a tubular chute, which is located around the inductor. The core is located in the inductor itself. The second option is called the crucible, because in it the metal with the crucible is already inside the indicator. Of course, there can be no talk of any core in this case.

In today's article we will talk about how to makeDIY induction oven.

Pros and cons of induction designs

Among the many benefits are the following:

• environmental cleanliness and safety;
• increased homogeneity of the melt due to the active movement of the metal;
• speed - the oven can be used almost immediately after switching on;
• zone and focused orientation of energy;
• high melting rate;
• lack of waste from alloying substances;
• the ability to adjust the temperature;
• numerous technical possibilities.

But there are also disadvantages.

1. The slag is heated by the metal, as a result of which it has a low temperature.
2. If the slag is cold, then it is very difficult to remove phosphorus and sulfur from the metal.
3. Between the coil and the melting metal, the magnetic field dissipates, so a reduction in lining thickness will be required. This will soon lead to the fact that the lining itself will fail.

Video - Induction furnace

Industrial Application

Both design options are used in the smelting of iron, aluminium, steel, magnesium, copper and precious metals. The useful volume of such structures can range from several kilograms to several hundred tons.

Furnaces for industrial use are divided into several types.

1. Medium frequency designs are commonly used in mechanical engineering and metallurgy. With their help, steel is melted, and when using graphite crucibles, non-ferrous metals are also melted.
2. Industrial frequency designs are used in iron smelting.
3. Resistance structures are intended for melting aluminum, aluminum alloys, zinc.

Note! It was induction technology that formed the basis of more popular devices - microwave ovens.

domestic use

For obvious reasons, the induction melting furnace is rarely used in the home. But the technology described in the article is found in almost all modern houses and apartments. These are the microwaves mentioned above, and induction cookers, and electric ovens.

Consider, for example, plates. They heat the dishes due to inductive eddy currents, as a result of which the heating occurs almost instantly. It is characteristic that it is impossible to turn on the burner on which there are no dishes.

The efficiency of induction cookers reaches 90%. For comparison: for electric stoves it is about 55-65%, and for gas stoves - no more than 30-50%. But in fairness, it is worth noting that the operation of the described stoves requires special dishes.

Homemade induction oven

Not so long ago, domestic radio amateurs clearly demonstrated that you can make an induction furnace yourself. Today, there are a lot of different schemes and manufacturing technologies, but we have given only the most popular of them, which means the most effective and easy to implement.

Induction furnace from high frequency generator

Below is an electrical circuit for making a homemade device from a high-frequency (27.22 megahertz) generator.

In addition to the generator, the assembly will require four high-power light bulbs and a heavy lamp for the ready-to-work indicator.

Note! The main difference between the furnace, made according to this scheme, is the condenser handle - in this case, it is located outside.

In addition, the metal in the coil (inductor) will melt in the device of the smallest power.

When manufacturing, it is necessary to remember some important points that affect the speed of metal boarding. This:

• power;
• frequency;
• eddy losses;
• heat transfer intensity;
• hysteresis loss.

The device will be powered by a standard 220 V network, but with a pre-installed rectifier. If the furnace is intended for heating a room, then it is recommended to use a nichrome spiral, and if for melting, then graphite brushes. Let's get acquainted with each of the structures in more detail.

Video - Welding inverter design

The essence of the design is as follows: a pair of graphite brushes is installed, and powdered granite is poured between them, after which a step-down transformer is connected. It is characteristic that when smelting, one can not be afraid of electric shock, since there is no need to use 220 V.

Assembly technology

Step 1. The base is assembled - a box of fireclay bricks measuring 10x10x18 cm, laid on a refractory tile.

Step 2. Boxing is finished with asbestos cardboard. After wetting with water, the material softens, which allows you to give it any shape. If desired, the structure can be wrapped with steel wire.

Note! The dimensions of the box may vary depending on the power of the transformer.

Step 3. The best option for a graphite furnace is a transformer from a 0.63 kW welding machine. If the transformer is designed for 380 V, then it can be rewound, although many experienced electricians say that you can leave everything as it is.

Step 4. The transformer is wrapped with thin aluminum - so the structure will not get very hot during operation.

Step 5. Graphite brushes are installed, a clay substrate is installed on the bottom of the box - so the molten metal will not spread.

The main advantage of such a furnace is the high temperature, which is suitable even for melting platinum or palladium. But among the minuses is the rapid heating of the transformer, a small volume (no more than 10 g can be smelted at a time). For this reason, a different design will be required for melting large volumes.

So, for the smelting of large volumes of metal, a furnace with nichrome wire is required. The principle of operation of the design is quite simple: an electric current is applied to a nichrome spiral, which heats up and melts the metal. There are a lot of different formulas on the Web for calculating the length of the wire, but they are all, in principle, the same.

Step 1. For the spiral, nichrome ø0.3 mm is used, about 11 m long.

Step 2. The wire must be wound. To do this, you need a straight copper tube ø5 mm - a spiral is wound on it.

Step 3. A small ceramic pipe ø1.6 cm and 15 cm long is used as a crucible. One end of the pipe is plugged with asbestos thread - so the molten metal will not flow out.

Step 4. After checking the performance and the spiral is laid around the pipe. At the same time, the same asbestos thread is placed between the turns - it will prevent a short circuit and limit the access of oxygen.

Step 5. The finished coil is placed in a cartridge from a high power lamp. Such cartridges are usually ceramic and have the required size.

The advantages of such a design:

• high productivity (up to 30 g per run);
• fast heating (about five minutes) and long cooling;
• ease of use - it is convenient to pour metal into molds;
• prompt replacement of the spiral in case of burnout.

But there are, of course, downsides:

• nichrome burns out, especially if the spiral is poorly insulated;
• insecurity - the device is connected to the mains 220 V.

Note! You can not add metal to the stove if the previous portion is already melted there. Otherwise, all the material will scatter around the room, moreover, it may injure the eyes.

As a conclusion

As you can see, you can still make an induction furnace on your own. But to be frank, the described design (like everything available on the Internet) is not quite a furnace, but a Kukhtetsky laboratory inverter. It is simply impossible to assemble a full-fledged induction structure at home.

Chief Editor

How to make an induction heater with your own hands?

Electric heaters

Induction heaters work on the principle of “getting current from magnetism”. In a special coil, a high-power alternating magnetic field is generated, which generates eddy electric currents in a closed conductor.

A closed conductor in induction cookers is metal utensils, which are heated by eddy electric currents. In general, the principle of operation of such devices is not complicated, and with little knowledge in physics and electrical engineering, it will not be difficult to assemble an induction heater with your own hands.

The following devices can be made independently:

1. Devices for heating the coolant in the heating boiler.
2. Mini ovens for melting metals.
3. Plates for cooking food.

Do-it-yourself induction cooker must be made in compliance with all norms and rules for the operation of these devices. If electromagnetic radiation dangerous for humans is emitted outside the case in the lateral directions, then it is strictly forbidden to use such a device.

In addition, a great difficulty in the design of the stove lies in the selection of material for the base of the hob, which must meet the following requirements:

1. Ideal for conducting electromagnetic radiation.
2. Not conductive.
3. Withstand high temperature stress.

In household induction hobs, expensive ceramics are used; in the manufacture of an induction cooker at home, it is rather difficult to find a worthy alternative to such material. Therefore, to begin with, you should design something simpler, for example, an induction furnace for hardening metals.

Manufacturing instructions

Figure 1. Electrical diagram of the induction heater
Figure 2. Device.
Figure 3. Scheme of a simple induction heater

For the manufacture of the furnace you will need the following materials and tools:

• soldering iron;
• solder;
• textolite board.
• mini drill.
• radioelements.
• thermal paste.
• chemical reagents for board etching.

Additional materials and their features:

1. To make a coil, which will emit an alternating magnetic field necessary for heating, it is necessary to prepare a piece of copper tube with a diameter of 8 mm and a length of 800 mm.
2. Powerful power transistors are the most expensive part of a homemade induction installation. To mount the frequency generator circuit, it is necessary to prepare 2 such elements. For these purposes, transistors of brands are suitable: IRFP-150; IRFP-260; IRFP-460. In the manufacture of the circuit, 2 identical of the listed field-effect transistors are used.
3. For the manufacture of an oscillatory circuit you will need ceramic capacitors with a capacity of 0.1 mF and an operating voltage of 1600 V. In order for a high-power alternating current to form in the coil, 7 such capacitors are required.
4. During the operation of such an induction device, field-effect transistors will get very hot and if aluminum alloy radiators are not attached to them, then after a few seconds of operation at maximum power, these elements will fail. Transistors should be placed on heat sinks through a thin layer of thermal paste, otherwise the efficiency of such cooling will be minimal.
5. Diodes, which are used in an induction heater, must be of ultra-fast action. The most suitable for this circuit, diodes: MUR-460; UV-4007; HER-307.
6. Resistors used in circuit 3: 10 kOhm with a power of 0.25 W - 2 pcs. and 440 ohm power - 2 watts. Zener diodes: 2 pcs. with an operating voltage of 15 V. The power of the zener diodes must be at least 2 watts. A choke for connecting to the power outputs of the coil is used with induction.
7. To power the entire device, you will need a power supply unit with a capacity of up to 500. W. and voltage 12 - 40 V. You can power this device from a car battery, but you will not be able to get the highest power readings at this voltage.

The very process of manufacturing an electronic generator and coil takes a little time and is carried out in the following sequence:

1. From a copper pipe a spiral with a diameter of 4 cm is made. To make a spiral, a copper tube should be wound onto a rod with a flat surface with a diameter of 4 cm. The spiral should have 7 turns that should not touch. Mounting rings are soldered to the 2 ends of the tube for connection to the transistor radiators.
2. The printed circuit board is made according to the scheme. If it is possible to supply polypropylene capacitors, then due to the fact that such elements have minimal losses and stable operation at large amplitudes of voltage fluctuations, the device will work much more stable. The capacitors in the circuit are installed in parallel, forming an oscillatory circuit with a copper coil.
3. Metal heating occurs inside the coil, after the circuit is connected to a power supply or battery. When heating the metal, it is necessary to ensure that there is no short circuit of the spring windings. If you touch the heated metal 2 turns of the coil at the same time, then the transistors fail instantly.

1. When conducting experiments on heating and hardening metals, inside the induction coil the temperature can be significant and amounts to 100 degrees Celsius. This heating effect can be used to heat domestic water or to heat a house.
2. Scheme of the heater discussed above (Figure 3), at maximum load it is able to provide the radiation of magnetic energy inside the coil equal to 500 watts. Such power is not enough to heat a large volume of water, and the construction of a high power induction coil will require the manufacture of a circuit in which it will be necessary to use very expensive radio elements.
3. A budget solution for organizing induction heating of a liquid, is the use of several devices described above, arranged in series. In this case, the spirals must be on the same line and not have a common metal conductor.
4. as a heat exchangera stainless steel pipe with a diameter of 20 mm is used. Several induction spirals are “strung” onto the pipe, so that the heat exchanger is in the middle of the spiral and does not come into contact with its turns. With the simultaneous inclusion of 4 such devices, the heating power will be about 2 kW, which is already enough for flow heating of the liquid with a small circulation of water, to values ​​\u200b\u200ballowing the use of this design in supplying warm water to a small house.
5. If you connect such a heating element to a well-insulated tank, which will be located above the heater, the result will be a boiler system in which the heating of the liquid will be carried out inside the stainless pipe, the heated water will rise up, and a colder liquid will take its place.
6. If the area of ​​the house is significant, the number of induction coils can be increased up to 10 pieces.
7. The power of such a boiler can be easily adjusted by turning off or on the spirals. The more sections that are simultaneously turned on, the greater the power of the heating device operating in this way will be.
8. To power such a module, you need a powerful power supply. If a DC inverter welding machine is available, then a voltage converter of the required power can be made from it.
9. Due to the fact that the system operates on direct electric current, which does not exceed 40 V, the operation of such a device is relatively safe, the main thing is to provide a fuse block in the generator power circuit, which, in the event of a short circuit, will de-energize the system, thereby eliminating the possibility of a fire.
10. It is possible to organize “free” heating of the house in this way, provided that batteries are installed to power induction devices, which will be charged using solar and wind energy.
11. Batteries should be combined in sections of 2, connected in series. As a result, the supply voltage with such a connection will be at least 24 V., which will ensure the operation of the boiler at high power. In addition, series connection will reduce the current in the circuit and increase the battery life.

1. Operation of homemade induction heating devices, does not always make it possible to exclude the spread of electromagnetic radiation harmful to humans, therefore the induction boiler should be installed in a non-residential area and shielded with galvanized steel.
2. Mandatory when working with electricity safety regulations must be followed and, especially for 220 V AC networks.
3. As an experiment you can make a hob for cooking according to the scheme indicated in the article, but it is not recommended to constantly operate this device due to the imperfection of self-manufacturing of the shielding of this device, because of this, the human body may be exposed to harmful electromagnetic radiation that can adversely affect health.

Induction heaters work on the principle of “getting current from magnetism”. In a special coil, a high-power alternating magnetic field is generated, which generates eddy electric currents in a closed conductor.

A closed conductor in induction cookers is metal utensils, which are heated by eddy electric currents. In general, the principle of operation of such devices is not complicated, and with little knowledge in physics and electrical engineering, it will not be difficult to assemble an induction heater with your own hands.

The following devices can be made independently:

1. Devices for heating in a heating boiler.
2. Mini ovens for melting metals.
3. Plates for cooking food.

Do-it-yourself induction cooker must be made in compliance with all norms and rules for the operation of these devices. If electromagnetic radiation dangerous for humans is emitted outside the case in the lateral directions, then it is strictly forbidden to use such a device.

In addition, a great difficulty in the design of the stove lies in the selection of material for the base of the hob, which must meet the following requirements:

1. Ideal for conducting electromagnetic radiation.
2. Not conductive.
3. Withstand high temperature stress.

In household induction hobs, expensive ceramics are used; in the manufacture of an induction cooker at home, it is rather difficult to find a worthy alternative to such material. Therefore, to begin with, you should design something simpler, for example, an induction furnace for hardening metals.

Manufacturing instructions

Blueprints

Figure 1. Electrical diagram of the induction heater
Figure 2. Device. Figure 3. Scheme of a simple induction heater

For the manufacture of the furnace you will need the following materials and tools:

• solder;
• textolite board.
• mini drill.
• radioelements.
• thermal paste.
• chemical reagents for board etching.

Additional materials and their features:

1. To make a coil, which will emit an alternating magnetic field necessary for heating, it is necessary to prepare a piece of copper tube with a diameter of 8 mm and a length of 800 mm.
2. Powerful power transistors are the most expensive part of a homemade induction installation. To mount the frequency generator circuit, it is necessary to prepare 2 such elements. For these purposes, transistors of brands are suitable: IRFP-150; IRFP-260; IRFP-460. In the manufacture of the circuit, 2 identical of the listed field-effect transistors are used.
3. For the manufacture of an oscillatory circuit you will need ceramic capacitors with a capacity of 0.1 mF and an operating voltage of 1600 V. In order for a high-power alternating current to form in the coil, 7 such capacitors are required.
4. During the operation of such an induction device, field-effect transistors will get very hot and if aluminum alloy radiators are not attached to them, then after a few seconds of operation at maximum power, these elements will fail. Transistors should be placed on heat sinks through a thin layer of thermal paste, otherwise the efficiency of such cooling will be minimal.
5. Diodes, which are used in an induction heater, must be of ultra-fast action. The most suitable for this circuit, diodes: MUR-460; UV-4007; HER-307.
6. Resistors used in circuit 3: 10 kOhm with a power of 0.25 W - 2 pcs. and 440 ohm power - 2 watts. Zener diodes: 2 pcs. with an operating voltage of 15 V. The power of the zener diodes must be at least 2 watts. A choke for connecting to the power outputs of the coil is used with induction.
7. To power the entire device, you will need a power supply unit with a capacity of up to 500. W. and voltage 12 - 40 V. You can power this device from a car battery, but you will not be able to get the highest power readings at this voltage.

The very process of manufacturing an electronic generator and coil takes a little time and is carried out in the following sequence:

1. From a copper pipe a spiral with a diameter of 4 cm is made. To make a spiral, a copper tube should be wound onto a rod with a flat surface with a diameter of 4 cm. The spiral should have 7 turns that should not touch. Mounting rings are soldered to the 2 ends of the tube for connection to the transistor radiators.
2. The printed circuit board is made according to the scheme. If it is possible to supply polypropylene capacitors, then due to the fact that such elements have minimal losses and stable operation at large amplitudes of voltage fluctuations, the device will work much more stable. The capacitors in the circuit are installed in parallel, forming an oscillatory circuit with a copper coil.
3. Metal heating occurs inside the coil, after the circuit is connected to a power supply or battery. When heating the metal, it is necessary to ensure that there is no short circuit of the spring windings. If you touch the heated metal 2 turns of the coil at the same time, then the transistors fail instantly.

Nuances

1. When conducting experiments on heating and hardening metals, inside the induction coil the temperature can be significant and amounts to 100 degrees Celsius. This heating effect can be used to heat domestic water or to heat a house.
2. Scheme of the heater discussed above (Figure 3), at maximum load it is able to provide the radiation of magnetic energy inside the coil equal to 500 watts. Such power is not enough to heat a large volume of water, and the construction of a high power induction coil will require the manufacture of a circuit in which it will be necessary to use very expensive radio elements.
3. A budget solution for organizing induction heating of a liquid, is the use of several devices described above, arranged in series. In this case, the spirals must be on the same line and not have a common metal conductor.
4. Asa stainless steel pipe with a diameter of 20 mm is used. Several induction spirals are “strung” onto the pipe, so that the heat exchanger is in the middle of the spiral and does not come into contact with its turns. With the simultaneous inclusion of 4 such devices, the heating power will be about 2 kW, which is already enough for flow heating of the liquid with a small circulation of water, to values ​​\u200b\u200ballowing the use of this design in supplying warm water to a small house.
5. If you connect such a heating element to a well-insulated tank, which will be located above the heater, the result will be a boiler system in which the heating of the liquid will be carried out inside the stainless pipe, the heated water will rise up, and a colder liquid will take its place.
6. If the area of ​​the house is significant, the number of induction coils can be increased up to 10 pieces.
7. The power of such a boiler can be easily adjusted by turning off or on the spirals. The more sections that are simultaneously turned on, the greater the power of the heating device operating in this way will be.
8. To power such a module, you need a powerful power supply. If a DC inverter welding machine is available, then a voltage converter of the required power can be made from it.
9. Due to the fact that the system operates on direct electric current, which does not exceed 40 V, the operation of such a device is relatively safe, the main thing is to provide a fuse block in the generator power circuit, which, in the event of a short circuit, will de-energize the system, thereby eliminating the possibility of a fire.
10. It is possible to organize “free” heating of the house in this way, provided that batteries are installed to power induction devices, which will be charged using solar and wind energy.
11. Batteries should be combined in sections of 2, connected in series. As a result, the supply voltage with such a connection will be at least 24 V., which will ensure the operation of the boiler at high power. In addition, series connection will reduce the current in the circuit and increase the battery life.

1. Operation of homemade induction heating devices, does not always make it possible to exclude the spread of electromagnetic radiation harmful to humans, therefore the induction boiler should be installed in a non-residential area and shielded with galvanized steel.
2. Mandatory when working with electricity safety regulations must be followed and, especially for 220 V AC networks.
3. As an experiment you can make a hob for cooking according to the scheme indicated in the article, but it is not recommended to constantly operate this device due to the imperfection of self-manufacturing of the shielding of this device, because of this, the human body may be exposed to harmful electromagnetic radiation that can adversely affect health.