Induction melting is a widely used process in ferrous and non-ferrous metallurgy. Melting in devices with induction heating is often superior to melting in fuel stoves on energy efficiency, product quality and production flexibility. These pre-

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properties are determined by specific physical characteristics induction furnaces.

In induction melting, the solid material is transferred into the liquid phase under the influence of electricity. magnetic field. As in the case of induction heating, heat is released in the melted material due to the Joule effect from induced eddy currents. The primary current passing through the inductor creates an electromagnetic field. Regardless of whether the electromagnetic field is concentrated by magnetic cores or not, the coupled inductor-load system can be represented as a transformer with a magnetic core or as an air transformer. The electrical efficiency of the system is highly dependent on the field-influencing characteristics of the ferromagnetic components.

Along with electromagnetic and thermal phenomena, electrodynamic forces play an important role in the induction melting process. These forces must be taken into account, especially in the case of melting in powerful induction furnaces. The interaction of induced electric currents in the melt with the resulting magnetic field causes a mechanical force (Lorentz force)

Pressure Melt flows

Rice. 7.21. Action of electromagnetic forces

For example, the force-induced turbulent movement of the melt is very important both for good heat transfer and for the mixing and adhesion of non-conducting particles in the melt.

There are two main types of induction furnaces: induction crucible furnaces (IFC) and induction channel furnaces (ICF). In ITP, the molten material is usually loaded in pieces into a crucible (Fig. 7.22). The inductor covers the crucible and the melted material. Due to the absence of a concentrating field of the magnetic circuit, the electromagnetic connection between

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inductor and loading strongly depends on the wall thickness of the ceramic crucible. To ensure high electrical efficiency, the insulation must be as thin as possible. On the other hand, the lining must be thick enough to withstand thermal stresses and

metal movement. Therefore, a compromise should be sought between electrical and strength criteria.

Important characteristics of induction melting in ITP are the movement of the melt and the meniscus as a result of the influence of electromagnetic forces. The movement of the melt ensures both uniform temperature distribution and homogeneous chemical composition. The mixing effect at the surface of the melt reduces material losses during additional loading of small-sized charge and additives. Despite the use of cheap material, the reproduction of a melt of constant composition ensures high quality casting.

Depending on the size, type of material being melted and the field of application, ITPs operate at industrial frequency (50 Hz) or medium frequency.

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at frequencies up to 1000 Hz. The latter are becoming increasingly important due to their high efficiency in melting cast iron and aluminum. Since the melt motion at constant power is weakened with increasing frequency, higher power densities and consequently greater productivity become available at higher frequencies. Due to the higher power, the melting time is reduced, which leads to an increase in the efficiency of the process (compared to furnaces operating at industrial frequency). Taking into account others technological advantages, such as flexibility in changing melted materials, mid-frequency ITPs are designed as high-power melting plants that currently dominate the iron foundry industry. Modern powerful mid-frequency ITS for cast iron melting have a capacity of up to 12 tons and a power of up to 10 MW. Industrial frequency ITPs are developed for large containers than mid-frequency ones, up to 150 tons for cast iron melting. Intensive mixing of the bath is of particular importance when smelting homogeneous alloys, such as brass, therefore, industrial frequency ITPs are widely used in this area. Along with the use of crucible furnaces for smelting, they are currently also used for holding liquid metal before casting.

In accordance with the energy balance of IHP (Fig. 7.23), the level of electrical efficiency for almost all types of furnaces is about 0.8. Approximately 20% of the initial energy is lost in the inductor in the form of Joe heat. The ratio of heat losses through the crucible walls to the electrical energy induced in the melt reaches 10%, so the total efficiency of the furnace is about 0.7.

The second widely used type of induction furnace is the IKP. They are used for casting, aging and, especially, melting in ferrous and non-ferrous metallurgy. The ICP generally consists of a ceramic bath and one or more induction units (Fig. 7.24). IN

In principle, the induction unit can be represented as a transform

The operating principle of the IKP requires the presence of a constantly closed secondary loop, so these furnaces operate with a liquid residue of the melt. Useful heat is generated mainly in the channel, which has a small cross-section. The circulation of the melt under the influence of electromagnetic and thermal forces ensures sufficient heat transfer into the bulk of the melt located in the bath. Until now, ICPs have been designed for industrial frequencies, but research work is also being carried out for higher frequencies. Thanks to the furnace's compact design and very good electromagnetic coupling, its electrical efficiency reaches 95%, and its overall efficiency reaches 80% and even 90%, depending on the material being melted.

According to the technological conditions in different fields of application, ICPs are required various designs induction channels. Single-channel furnaces are mainly used for aging and casting,

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steel melting is less common at installed capacities of up to 3 MW. For melting and holding non-ferrous metals, two-channel designs are preferable, providing best use energy. In aluminum melting plants, the channels are made straight for ease of cleaning.

The production of aluminum, copper, brass and their alloys is the main area of ​​application of IKP. Today, the most powerful ICPs with a capacity

up to 70 tons and a power of up to 3 MW are used for aluminum smelting. Along with high electrical efficiency, low melt losses are very important in aluminum production, which predetermines the choice of ICP.

Promising applications of induction melting technology include the production of high-purity metals such as titanium and its alloys in cold crucible induction furnaces and the melting of ceramics such as zirconium silicate and zirconium oxide.

When melting in induction furnaces, the advantages of induction heating are clearly demonstrated, such as high energy density and productivity, homogenization of the melt due to stirring, precise

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energy and temperature control, as well as ease of automatic process control, ease of manual control and greater flexibility. High electric and thermal efficiency combined with low melt losses and, therefore, raw material savings, result in low specific consumption energy and environmental competitiveness.

The superiority of induction melting devices over fuel ones is continuously increasing thanks to practical research supported by numerical methods for solving electromagnetic and hydrodynamic problems. As an example, we can note the internal coating of the IKP steel casing with copper strips for copper smelting. Reducing eddy current losses increased the efficiency of the furnace by 8%, and it reached 92%.

Further improvement of the economic performance of induction melting is possible through the use of modern technologies controls such as tandem or dual power control. Two tandem ITPs have one power source, and while melting is underway in one, the molten metal is held in the other for casting. Switching the power source from one furnace to another increases its utilization. A further development of this principle is dual power control (Fig. 7.25), which ensures long-term simultaneous operation of furnaces without switching using special automatic process control. It should also be noted that an integral part of the economics of smelting is the compensation of total reactive power.

In conclusion, to demonstrate the advantages of energy- and material-saving induction technology, we can compare fuel and electrothermal methods for melting aluminum. Rice. 7.26 shows a significant reduction in energy consumption per ton of aluminum when melting in

Chapter 7. Energy-saving capabilities of modern electrical technologies

□ metal loss; Shch melting

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induction channel furnace with a capacity of 50 tons. The final energy consumption is reduced by approximately 60%, and the primary energy by 20%. At the same time, CO2 emissions are significantly reduced. (All calculations are based on typical German energy conversion and CO2 emission coefficients for mixed power plants). The results obtained highlight the special influence of metal losses during melting associated with its oxidation. Their compensation requires a large additional expenditure of energy. It is noteworthy that in copper production, metal losses during smelting are also large and must be taken into account when choosing a particular smelting technology.

Induction heating is impossible 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. Generator alternating current used to obtain high-frequency flow from the standard flow of the home electrical network with a frequency of 50 Hz. A metal object capable of absorbing thermal energy under the influence of a magnetic field is used as a heating element.

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

The operating principle 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 direction at high frequencies electromagnetic waves. 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 supplied from the inverter to the induction coil creates a magnetic field with a constantly changing vector of magnetic waves. Metal placed in this field heats up quickly

The absence 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. The water simultaneously cools the heater, which significantly increases its service life.

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

Literature

• Babat G. I., Svenchansky A. D. Electric industrial furnaces. - M.: Gosenergoizdat, 1948. - 332 p.
• Burak Ya. I., Ogirko I. V. Optimal heating of a cylindrical shell with temperature-dependent material characteristics // Mat. methods and physical-mechanical fields. - 1977. - Issue. 5 . - pp. 26-30.
• Vasiliev A. S. Tube generators for high frequency heating. - L.: Mechanical Engineering, 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. Basics of radio engineering. - M.: Gosenergoizdat, 1959. - 512 p.
• Lozinsky M. G. Industrial application of induction heating. - M.: Publishing House of the USSR Academy of Sciences, 1948. - 471 p.
• Application of high frequency currents in electrothermy / Ed. A. E. Slukhotsky. - L.: Mechanical Engineering, 1968. - 340 p.
• Slukhotsky A. E. Inductors. - L.: Mechanical Engineering, 1989. - 69 p. - (Library of high-frequency thermist; Issue 12). - 10,000 copies. - ISBN 5-217-00571-8.
• Fogel A. A. Induction method for keeping liquid metals in suspension / Ed. A. N. Shamova. - 2nd ed., rev. - L.: Mechanical Engineering, 1989. - 79 p. - (Library of high-frequency thermist; Issue 11). - 2950 copies. - .

Operating principle

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

Operating principle of induction heating installation

The water supplied through the lower pipe to the boiler is heated by energy transfer and exits through the upper pipe, entering the heating system. A built-in pump is used to create pressure. Constantly circulating water in the boiler prevents the elements from overheating. In addition, during operation the coolant vibrates (at a low noise level), due to which scale deposits on the internal 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 sources, the calculation of an induction furnace begins with calculating the power of the unit.

The power of an 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 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 necessary to take into account the metal or alloy being melted: according to the condition, it is zinc. This is an important point, the heat balance of cast iron melting in an induction furnace, as well as other alloys, is different.

Useful power transferred to liquid metal:

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

Active power:

• P = Ppol/Yuterm,
• Rpol – taken from the previous formula, kW;
• Yuterm is the efficiency of a foundry furnace, its limits are from 0.7 to 0.85, with an average of 0.76.
• P = 1311.2/0.76 = 1892.1 kW, the value is rounded to 1900 kW.

At the final stage, the inductor power is calculated:

• Rind = P/N,
• R - active power furnace installation, kW;
• N is the number of inductors provided on the furnace.
• Rind =1900/2= 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 making a mini induction oven with your own hands, then it is important to know that its main element is the heating coil. When homemade version it is enough to use an inductor made of a bare copper tube, the diameter of which is 10 mm

For the inductor, an internal 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 should not come into contact with its screen; the minimum gap should be 50 mm.

If you are planning to make an induction furnace with your own hands, then you should know that on an industrial scale, water or antifreeze is used to cool the inductors. When low power and short work created device You can do without cooling. But during operation, the inductor gets very hot, and scale on copper can not only sharply reduce the efficiency of the device, but also lead to a complete loss of its performance. It is impossible to make a cooled inductor on your own, so it will need to be replaced regularly. You cannot use forced air cooling, since the fan housing placed close to the coil will “attract” EMF, 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 an automatic frequency control circuit (PLL) and operates from an external master oscillator (at a frequency close to the resonant frequency of the oscillatory circuit “inductor - compensating capacitor bank”). At the moment a workpiece made of magnetic material is introduced into the inductor (if the dimensions of the workpiece are large enough and commensurate with the dimensions of the inductor), the inductance of the inductor increases sharply, which leads to a sudden 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 a sudden decrease in the power transmitted to the workpiece. If the power of the installation is regulated by an external power source, then the natural reaction of the operator is to increase the supply voltage of the installation. When the workpiece is heated to the Curie point, its magnetic properties disappear, and the natural frequency of the oscillatory circuit returns back to the frequency of the master oscillator. The circuit resistance decreases sharply, and the current consumption increases sharply. If the operator does not have time to remove the increased supply voltage, the installation will overheat and fail.
If the installation is equipped with an automatic control system, then the control system must 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 heated, then the above does not matter. The introduction of a workpiece 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 there are many workpiece sizes smaller sizes inductor, then it also does not greatly shift the resonance of the operating circuit.

Induction cookers

Main article: Induction cooker

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

Such a stove has a higher efficiency compared to electric heating elements, since less heat is spent on heating the body, and in addition there is no acceleration and cooling period (when the energy generated, but not absorbed by the cookware, is wasted).

Induction melting furnaces

Main article: Induction crucible furnace

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

It is used in foundries of factories, as well as in precision casting shops and repair shops of machine-building plants to produce high-quality steel castings. It is possible to melt non-ferrous metals (bronze, brass, aluminum) and their alloys in a graphite crucible. An induction furnace operates on the principle of a transformer, in which the primary winding is a water-cooled inductor, and the secondary and at the same time load is the metal located in the crucible. Heating and melting of the metal occurs 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 field lines of which intersect the conducting circuit. The current in the circuit is called induction. The law of electromagnetic induction is the basis for the invention of many devices, including the defining 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 Emil Lenz) formulated quantification thermal effect of electric current: “The power of heat released per unit volume of a medium during the flow of electric current is proportional to the product of the electric current density and the magnitude of the electric field strength” (Joule-Lenz law). The thermal effect of induced current gave rise to the search for devices for non-contact heating of metals. The first experiments on heating steel using induction current were made by E. Colby in the USA.

The first successfully operating so-called. The channel induction furnace for melting steel was built in 1900 by Benedicks Bultfabrik in Gysing, Sweden. In the respectable magazine of that time “THE ENGINEER” on July 8, 1904, a famous one 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 furnace with a capacity of 78 kW was put into operation on March 18, 1900 and turned out 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 power of 58 kW and a steel capacity of 100 kg. The furnace showed high efficiency; the melting capacity was from 600 to 700 kg of steel per day. However, wear from thermal fluctuations turned out to be at an unacceptable level, and frequent lining replacements reduced the final efficiency.

The inventor came to the conclusion that for maximum melting performance it is necessary to leave a significant part of the melt when draining, which avoids many problems, including wear of the lining. This method of smelting steel with a residue, which came to be called “swamp,” is still preserved in some industries that use large-capacity furnaces.

In May 1902, a significantly improved furnace with a capacity of 1800 kg was put into operation, the discharge was 1000-1100 kg, the remainder 700-800 kg, power 165 kW, steel melting capacity could reach 4100 kg per day! This result in energy consumption of 970 kWh/t is impressive in its efficiency, which is not much inferior to modern productivity of about 650 kWh/t. According to the inventor's calculations, out of a power consumption of 165 kW, 87.5 kW was lost, the useful thermal power was 77.5 kW, and a very high total efficiency of 47% was obtained. The cost-effectiveness is explained by the annular 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, are equipped with many improvements over a hundred years of their development, but the efficiency is increased immaterial. True, the inventor in his publication ignored the fact that electricity is paid not for active power, but for total 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, 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, which converts direct voltage into alternating voltage. For such cases, use a cable with a cross section of 6-8 mm, but not standard for welding machines at 2.5 mm.

Such heating systems must be of a closed type and controlled automatically. For other safety, you need a pump that will provide circulation 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 by at least 1 meter.

Implementation in domestic conditions

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 household use– from 25,000 rub. and higher. Therefore, the interest in circuits that allow you to create a homemade induction heater with your own hands is quite understandable.

induction heating boiler

Transformer based

The main element of the system induction heating with a transformer will be the device itself, which has a primary and secondary winding. 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, implemented physically 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 an 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. The toroidal winding of copper wire is made along the outer tube. It is necessary to apply from 85 to 100 turns with an equal distance between the turns. Alternating current, changing over time, creates vortex flows in a closed circuit, which heat the core, and therefore the coolant, carrying out 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 power supply frequency of 50 Hz to a current with a higher frequency. This modulated current is supplied to a cylindrical inductor coil, 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 a frequency specified by the generator. The created eddy currents induced by the magnetic field produce heating of the metal element, which transfers energy to the coolant. In this way, another do-it-yourself induction heating scheme is implemented.

The heating element can also be created with your own hands from cut metal wire about 5 mm long and a piece of 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 left. According to the diagram, about 100 turns of copper wiring are placed 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 provide reliable thermal insulation, otherwise the efficiency of the heating system will drop significantly. .

Advantages and disadvantages of the device

There are a lot of “advantages” of a vortex induction heater. 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 productivity of the device can be significant; units of this type are successfully used in the metallurgical industry. In terms of heating rate 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 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 should be protected from these contaminants using a mechanical filter.

An induction coil heats the metal (pipe or pieces of wire) placed inside it using high frequency eddy currents, no contact required

Constant contact with water minimizes the likelihood of the heater burning out, which is a fairly common problem for traditional boilers with heating elements. Despite the vibration, the boiler operates extremely quietly; additional sound insulation at the installation site is not required.

Another good thing about induction boilers is that they almost never leak, unless the system is installed correctly. The absence of leaks is due to the non-contact method of transferring thermal energy to the heater. Using the technology described above, the coolant can be heated almost to a vapor state.

This provides sufficient thermal convection to encourage efficient movement of 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 design of the specific heating system.

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

But this convenient and reliable device has a number of disadvantages that should also be taken into account. For example, a boiler heats not only the coolant, but also the entire working space surrounding it. It is necessary to allocate a separate room for such a unit and remove all foreign objects from it. For a person, staying in close proximity to a working boiler for a long time can also be unsafe.

Induction heaters require electric current to operate. Both homemade and factory-made equipment are connected to a household AC network

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

If the device is handled carelessly, an explosion may occur.

If you overheat the coolant, it will turn into steam. As a result, the pressure in the system will increase sharply, which the pipes simply cannot withstand and will burst. Therefore, for 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 virtually silent, this is not always the case. Some models may still produce some noise for various reasons. For a device made independently, the likelihood of such an outcome increases.

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

Homemade induction boilers

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

The homemade induction heater was then tested by filling it with water and connecting it to a factory-made ORION 2 kW induction cooktop instead of the stock inductor. The test results are shown in the following video:

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

• The author did a good job and his product undoubtedly works.
• No calculations were made on the thickness of the wire, the number and diameter of the coil turns. The winding parameters were adopted by analogy with the hob; accordingly, the induction water heater will have a power of no more than 2 kW.
• In the best case, a homemade unit will be able to heat water for two heating radiators of 1 kW each, which 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 coolant flow.

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

The radiator, welded from several metal pipes, acts as an external core for the 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 pipes were chosen randomly but provided sufficient surface area to transfer the heat generated by the eddy currents.
• This induction heater circuit turned out to be successful for a specific case where 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 recording of the air temperature in the rooms.

To confirm the conclusions drawn, it is proposed to watch a video where the author tried to use a similar heater in a free-standing, insulated building:

Operating principle

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

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

The inductor-blank system is a coreless transformer in which the inductor is the primary winding. The workpiece is like a secondary winding, short-circuited. The magnetic flux between the windings is closed through the air.

At high frequencies, eddy currents are displaced by the magnetic field they themselves generate into thin surface layers of the workpiece Δ ​​(skin effect), as a result of which their density increases sharply and the workpiece heats up. The underlying layers of 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 by e times relative to the current density in the workpiece, while 86.4% of the heat of 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 hundred 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 unity.

Formula for calculating skin depth in mm:

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

Where ρ - specific electrical resistance workpiece material at 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 becomes very hot during operation, as it absorbs its own radiation. In addition, it absorbs thermal radiation from the hot workpiece. Inductors are made from copper tubes cooled by water. Water is supplied by suction - this ensures safety in case of burnout or other depressurization of the inductor.

Operating principle

The melting unit of an 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 made of stainless steel or aluminum.
4. Contact area.
5. The hearth is made of heat-resistant concrete.
6. Support with hydraulic cylinder and bearing unit.

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

Advantages of the device

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

1. The use of the induction principle makes it possible to make the equipment compact. That is why there are no problems with their placement in small spaces. An example is blast furnaces, which can be installed exclusively in prepared rooms.
2. The results of the studies indicate that the efficiency is almost 100%.
3. High melting speed. The high efficiency rate determines that it takes much less time to heat the metal when compared with other furnaces.
4. When melting in some furnaces, the chemical composition of the metal can change. Induction takes first place in terms of melt purity. The created Foucault currents heat the workpiece from the inside, thereby eliminating the possibility of various impurities entering the composition.

It is this last advantage that determines the spread of induction furnaces in jewelry, since even a small concentration of foreign impurities can negatively affect the result obtained.

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 in everyday life:

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

The opening is also used for an extruder (not mechanical). Previously, it was widely used in metallurgy and other industries related to metal processing. A factory inductive boiler operates on the principle of the action of eddy currents on a special core located in the internal part 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 alternating electrical voltage to the winding, causing the appearance of an alternating electric magnetic field, which changes potentials 50 times/sec. at a standard industrial frequency of 50 Hz.

In this case, the Ruhmkorff induction coil is designed in such a way that it can be connected directly to an AC power supply. In production, high-frequency electric currents are used for such heating - up to 1 MHz, so it is quite difficult to achieve the operation of the device at 50 Hz. The thickness of the wire and the number of winding turns that the device uses are calculated separately for each unit using a special method for the required heat power. A homemade, powerful unit must function efficiently, quickly heat the water flowing through the pipe and not heat up.

Organizations invest serious funds in the development and implementation of such products, therefore:

• All problems are resolved successfully;
• Efficiency heating device has 98%;
• Functions without interruption.

In addition to the highest efficiency, one cannot help but be attracted by the speed at which the medium passing through the core is heated. In Fig. A diagram of the functioning of an induction water heater created at the plant is proposed. Such a scheme has a unit of the “VIN” brand, which is produced by the Izhevsk plant.

How long the unit will operate depends solely on how sealed the housing is and how the insulation of the wire turns is not damaged, and this is quite a significant period, according to the manufacturer - up to 30 years.

For all these advantages, which the device 100% has, you need to shell out a lot of money; an induction, magnetic water heater is the most expensive of all types of heating installations. Therefore, many craftsmen prefer to assemble an ultra-economical heating unit themselves.

Rules for making equipment yourself

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, more).

• The wire should be cut into pieces no larger than five centimeters. This is needed 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 mesh 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 structure is closed and the adapter is installed.
• 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 device. The coil is connected to the prepared inverter.
• A water supply pump is installed.
• A temperature regulator 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 buses leading to the inductor, which can be much greater than the inductor itself.

High precision induction heating

This heating has the simplest principle, since it is non-contact. High-frequency pulse heating makes it possible to achieve the highest temperature conditions, at which it is possible to process the most difficult metals to melt. To perform induction heating, you need to create the required voltage of 12V (volts) and inductance frequency 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 flowing currents heat the tube, which subsequently supplies heat to the living space.

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

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

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

Heating can solve many problems.

What is induction heating

The principle on which an induction water heater works.

An induction device operates on energy generated by an 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 wire coil of cylindrical shape.
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 electrical energy 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 period of time.

Features of the device

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 arise in the deep part of the transformer. They redirect the emerging electromagnetic field to the secondary circuit. It simultaneously functions as a housing and acts as a heating element for water.

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

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

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

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

An induction water heater consists of the following structural elements:

Photo	Structural unit
	Inductor. It consists of many turns of copper wire. It is in them that the electromagnetic field is generated.
	A heating element. This is a metal pipe or pieces of steel wire placed inside the inductor.
	Generator. It transforms household electricity into high-frequency electric current. The role of a generator can be played by an inverter from a welding machine.

Diagram of operation of a heating system with an induction water heater.

When all components of the device interact, thermal energy is generated and transferred to water. The operating diagram of the unit is as follows:

1. The generator produces high-frequency electric current. It then transmits it to the induction coil.
2. It receives the current and transforms it into an electric magnetic field.
3. The heater located inside the coil heats up from 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 require frequent maintenance;
• they take up little free space;
• due to vibrations of the magnetic field, scale does not settle inside them;
• the 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, carbon monoxide, etc.

The photo shows 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 out if you assemble an induction heater with your own hands. The unit is assembled from easily accessible elements, their price is low.

Benefits of using all types of induction heaters

An induction heater has undoubted advantages and is a leader among all types of devices. This advantage is as follows:

• It consumes less electricity and does not pollute the surrounding space.
• Easy to use, it provides high quality work and allows you to control the process.
• Heating through the walls of the chamber ensures special purity and the ability to obtain ultra-pure alloys, while melting can be carried out in different atmospheres, including inert gases and in a vacuum.
• With its help, it is possible to uniformly heat parts of any shape or selective heating
• Finally, induction heaters are universal, which allows them to be used everywhere, displacing 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, you must follow 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 circuit of a simple induction heater provides for such moments.
2. The inverter is connected to the network only through an RCD. This device operates in critical situations and will help avoid short circuits.
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 induction heater body must be placed at a height of 80 cm above the floor level. 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 produces a very strong electromagnetic field, so such an installation should be kept away from living quarters and enclosures with pets.

Induction heater circuit

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

A factory induction boiler uses in its operation 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.

Operating principle of an induction heater

The occurrence of currents is due to the supply of 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. In this case, the induction coil is designed in such a way that it can be connected to the AC mains directly. In industry, high-frequency currents are used for such heating - up to 1 MHz, so it is quite difficult to achieve operation of the device at a frequency of 50 Hz.

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

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

Heater operation diagram

The longevity of the heat generator depends only on the tightness of the housing and the integrity of the insulation of the wire turns, and this turns out to be a fairly long period; manufacturers declare up to 30 years. For all these advantages that these devices actually have, you have to pay a lot of money; an induction water heater is the most expensive of all types of electrical heating installations. For this reason, some craftsmen have taken to making a homemade device with the goal of using it to heat a house.

DIY process

The following tools will be useful for the job:

• welding inverter;
• welding generating current from 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 length of material needed to assemble the core must be required length. On average, the number of turns is 50, the wire diameter is 3 millimeters.

Copper wire of different diameters for winding

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

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

First option

The wire is cut into 50 mm sections and a plastic tube is filled with it. To prevent it from spilling out of the pipe, you should seal the ends with wire mesh. Adapters from the pipe are placed at the ends, in the place where the heater is connected.

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

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

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

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

Second option

This option is much simpler. A straight meter-sized section is selected on the vertical part of the pipe. It should be thoroughly cleaned of paint using sandpaper. Next, 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 completely completed.

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 you understand the initial data of homemade equipment and avoid possible errors.

Third option

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

Winding on the inductor body

To supply and drain water, 2 pipes are welded into the body of the induction unit. In order not to lose heat and prevent possible current leaks, you need to make insulation. It will eliminate the problems described above and completely eliminate noise during boiler operation.

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

1. When the equipment is operating, there is a high load on the electrical network. In order to eliminate the possibility of a short circuit due to insulation wear, 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 reliable water rise.
3. If you are installing a tabletop stove, you should pay attention to the stability of the base used.
4. A furnace for melting metal is a complex electrical device, when installing which you must follow all the manufacturer’s recommendations. Particular attention is paid to the parameters of the power source, which must correspond to the device model.
5. Do not forget that there should be quite a lot of free space around the stove. During operation, even a small melt in volume and mass can accidentally splash out of the mold. At temperatures above 1000 degrees Celsius, it will cause irreparable harm various materials, and may also cause a fire.

The device may become very hot during operation. That is why there should be no flammable or explosive substances nearby. In addition, according to fire safety precautions in the vicinity, a fire shield must be installed.

Safety regulations

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


To prevent disruptions in the operation of the electrical network, it is recommended to connect a boiler with induction heating, made by hand according to the proposed diagrams, to a separate supply line, the cable cross-section of which will be at least 5 mm2

Conventional wiring may not be able to handle the required power consumption.

1. Induction heating systems require a safety valve to release water and steam in case the pump fails.
2. A pressure gauge and an RCD are required for the safe operation of a heating system assembled by yourself.
3. Having the entire induction heating system grounded and electrically insulated will prevent electric shock.
4. To avoid the harmful effects of the electromagnetic field on the human body, it is better to move such systems outside the residential area, where installation rules must be followed, according to which the induction heating device must 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 coolant.
6. To prevent failures in the operation of the electrical network, it is recommended to connect a boiler with induction heating, made by hand according to the proposed schemes, to a separate supply line, the cable cross-section of which will be at least 5 mm2. Conventional wiring may not be able to handle the required power consumption.

Creation of sophisticated devices

Making a HDTV heating installation with your own hands is more difficult, but radio amateurs can do it, because to assemble 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 draft. 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, as long as you have car batteries as power sources. Of course, it is not powerful enough to melt metal, but it can reach the high temperatures necessary for small jobs, such as heating knives and screwdrivers 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 decreases to 6 A during heating due to metal resistance, 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 use it to build a resonance of 100k through the regulator. The circuit must be controlled via a network adapter with a voltage of 12 V or more. The power section can be connected directly to the main network of 220 V using diode bridge. The resonance frequency is 30 kHz. The following items will be required:

• 10 mm ferrite core and 20 turns inductor;
• copper tube as a HDTV coil of 25 turns on a 5-8 cm mandrel;
• capacitors 250 V.

Vortex heaters

A more powerful installation capable of heating bolts up to yellow color, 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, rated at 15 V;
• simple resistors.

Depending on the desired result, winding the wire on a copper base ranges from 10 to 30 turns. Next comes the assembly of the circuit and the preparation of the base coil of the heater from approximately 7 turns of 1.5 mm copper wire. It is connected 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, you need to weld the bases of two pipes, which will serve as both a core and a heater, and weld two pipes into the housing after the winding to supply and remove coolant.

Advantages and disadvantages

Having understood the operating principle of an induction heater, you can consider its positive and negative aspects. Considering the high popularity of heat generators of this type, it can be assumed that it has much more advantages than disadvantages. Among the most significant advantages are:

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

Since the performance indicator of an induction boiler is in a wide range, you can easily select a unit for a specific building heating system. These devices are capable of quickly heating the coolant to a given temperature, which 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 often. 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. Device for induction hob.

If no mistakes were made during the installation of the induction boiler, then leaks are 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. In this way, efficient movement of water through the pipes is achieved, and in some situations it is even possible to do without 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, in regions with frequent power outages it will not be able to operate with maximum efficiency. When the coolant overheats, the pressure in the system increases sharply and the pipes can burst. To avoid this, the induction heater must be equipped with an emergency shutdown device.

DIY induction heater

Working principle of induction heating

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, i.e. 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 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 penetrated by the flux of the magnetic induction vector, which constantly changes over time. In this case, an electric field arises, the lines of which are perpendicular to the direction of the magnetic flux and move in a closed 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 noticeably. This principle is widely used in the field of metal processing: melting, forging, soldering, surfacing, 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 wide range power 15-160 kW. The high-frequency type provides shallow heating, but this is enough to improve the chemical properties of the metal.

High-frequency induction heaters are easy to operate and economical, and their efficiency can reach 95%. All types operate 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 protection, each of which is responsible for its own function. Example: monitoring water pressure in a 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 Ekaterinburg
• Induction heater 160 kW Samara

Application:

• surface hardening of gear
• hardening of shafts
• hardening of crane wheels
• heating parts before bending
• soldering of cutters, milling cutters, drill bits
• heating the workpiece during hot stamping
• landing bolts
• welding and surfacing of metals
• restoration of parts.

The article discusses the designs of industrial induction melting furnaces (channel and crucible) and induction hardening plants powered by machine and static frequency converters.

Diagram of an induction channel furnace

Almost all industrial duct induction furnace designs are made with detachable induction units. The induction unit is an electric furnace transformer with a lined channel to accommodate the molten metal. The induction unit consists of the following elements: casing, magnetic core, lining, inductor.

Induction units are made as single-phase or two-phase (dual) with one or two channels per inductor. The induction unit is connected to the secondary side (LV side) of the electric furnace transformer using contactors having arc suppression devices. Sometimes two contactors with parallel operating power contacts in the main circuit are switched on.

In Fig. Figure 1 shows the power supply diagram for a single-phase induction unit of a channel furnace. Maximum current relays PM1 and PM2 are used to control and turn off the furnace in case of overloads and short circuits.

Three-phase transformers are used to power three-phase or two-phase furnaces that have either a common three-phase magnetic core or two or three separate core-type magnetic cores.

To power the furnace during the period of refining the metal and to maintain the idle mode, autotransformers are used to more accurately regulate the power during the period of finishing the metal to the desired chemical composition (in a calm, without seething, melting mode), as well as for the initial starts of the furnace during the first melts, which are carried out with a small volume of metal in the bath to ensure gradual drying and sintering of the lining. The power of the autotransformer is chosen within 25-30% of the power of the main transformer.

To control the temperature of water and air cooling the inductor and the casing of the induction unit, electric contact thermometers are installed that issue a signal when the temperature exceeds the permissible one. The power to the furnace is automatically turned off when the furnace is turned to drain the metal. To control the position of the furnace, limit switches are used, interlocked with the electric furnace drive. At ovens and mixers continuous action When draining the metal and loading new portions of the charge, the induction units are not switched off.

Rice. 1. Schematic diagram power supply of the induction unit of a channel furnace: VM - power switch, CL - contactor, Tr - transformer, C - capacitor battery, I - inductor, TN1, TN2 - voltage transformers, 777, TT2 - current transformers, R - disconnector, PR - fuses, RM1, RM2 - maximum current relay.

To ensure reliable power supply during operation and in emergency situations, the drive motors of the tilting mechanisms of the induction furnace, fan, drive of loading and unloading devices and control systems are powered from a separate auxiliary transformer.

Diagram of an induction crucible furnace

Industrial induction crucible furnaces with a capacity of more than 2 tons and a power of over 1000 kW are powered by three-phase step-down transformers with secondary voltage regulation under load, connected to high voltage network industrial frequency.

The furnaces are single-phase, and to ensure uniform load of the network phases, a balun device is connected to the secondary voltage circuit, consisting of a reactor L with inductance regulation by changing the air gap in the magnetic circuit and a capacitor bank Cc, connected with an inductor according to a triangle diagram (see ARIS in Fig. .2). Power transformers with a capacity of 1000, 2500 and 6300 kV-A have 9 - 23 stages of secondary voltage with automatic power control at the desired level.

Furnaces of smaller capacity and power are powered by single-phase transformers with a power of 400 - 2500 kV-A; with a power consumption of over 1000 kW, balun devices are also installed, but on the HV side of the power transformer. With a lower furnace power and power supply from a high-voltage network of 6 or 10 kV, you can dispense with the balun device if the voltage fluctuations when turning the furnace on and off are within acceptable limits.

In Fig. Figure 2 shows the power supply diagram for an industrial frequency induction furnace. The furnaces are equipped with ARIR electrical mode regulators, which, within specified limits, ensure the maintenance of voltage, power Рп and cosphi by changing the number of voltage steps of the power transformer and connecting additional sections of the capacitor bank. Regulators and measuring equipment are located in control cabinets.

Rice. 2. Power supply circuit for an induction crucible furnace from a power transformer with a balun device and furnace mode regulators: PSN - voltage step switch, C - balun capacitance, L - reactor of the balun device, S-St - compensating capacitor bank, I - furnace inductor, ARIS - balun regulator, ARIR - mode regulator, 1K-NK - battery capacity control contactors, TT1, TT2 - current transformers.

In Fig. Figure 3 shows a schematic diagram of power supply for induction crucible furnaces from a medium frequency machine converter. The furnaces are equipped with automatic electrical mode regulators, a crucible “eating” alarm system (for high-temperature furnaces), as well as an alarm for cooling failure in the water-cooled elements of the installation.

Rice. 3. Power supply circuit for an induction crucible furnace from a medium frequency machine converter with a block diagram of automatic control of the melting mode: M - drive motor, G - medium frequency generator, 1K-NK - magnetic starters, TI - voltage transformer, TT - current transformer, IP - induction furnace, C - capacitors, DF - phase sensor, PU - switching device, UFR - amplifier-phase regulator, 1KL, 2KL - linear contactors, BS - comparison unit, BZ - protection unit, OV - excitation winding, RN - voltage regulator.

Scheme of induction hardening installation

In Fig. 4 shows the fundamental electrical diagram power supply of the induction hardening machine from a machine frequency converter. Besides the power supply M-G scheme includes a power contactor K, a hardening transformer TrZ, on the secondary winding of which an inductor I is connected, a compensating capacitor bank Sk, voltage and current transformers TN and 1TT, 2TT, measuring instruments (voltmeter V, wattmeter W, phase meter) and generator current ammeters and excitation current, as well as a maximum current relay 1РМ, 2РМ to protect the power source from short circuits and overloads.

Rice. 4. Schematic electrical diagram of an induction hardening installation: M - drive motor, G - generator, TN, TT - voltage and current transformers, K - contactor, 1PM, 2RM, ZRM - current relay, Rk - arrester, A, V, W - measuring instruments, TRZ - hardening transformer, OVG - generator excitation winding, RR - discharge resistor, PB - excitation relay contacts, PC - adjustable resistance.

To power old induction installations for heat treatment of parts, electric machine frequency converters are used - a drive motor of a synchronous or asynchronous type and a medium-frequency generator of an inductor type; in new induction installations - static frequency converters.

The circuit of an industrial thyristor frequency converter for powering an induction hardening installation is shown in Fig. 5. The thyristor frequency converter circuit consists of a rectifier, a block of chokes, a converter (inverter), control circuits and auxiliary components (reactors, heat exchangers, etc.). According to the method of excitation, inverters are made with independent excitation (from the master oscillator) and with self-excitation.

Thyristor converters can operate stably both with a change in frequency over a wide range (with a self-adjusting oscillatory circuit in accordance with changing load parameters), and at a constant frequency with a wide range of changes in load parameters due to changes in the active resistance of the heated metal and its magnetic properties (for ferromagnetic parts).

Rice. 5. Schematic diagram of the power circuits of a thyristor converter type TPC-800-1: L - smoothing reactor, BP - starting unit, VA - automatic switch.

The advantages of thyristor converters are the absence of rotating masses, low loads on the foundation and the small influence of the power utilization factor on the reduction in efficiency; the efficiency is 92 - 94% at full load, and at 0.25 it decreases by only 1 - 2%. In addition, since the frequency can be easily changed within a certain range, there is no need to adjust the capacitance to compensate for the reactive power of the oscillating circuit.

An induction furnace is a furnace apparatus that is used for melting non-ferrous (bronze, aluminum, copper, gold and others) and ferrous (cast iron, steel and others) metals due to the operation of an inductor. A current is produced in the field of its inductor, it heats the metal and brings it to a molten state.

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First, it will be affected by an electromagnetic field, then by an electric current, and then it will go through the thermal stage. The simple design of such a stove device can be assembled independently from various available materials.

Principle of operation

Such a furnace device is an electrical transformer with a secondary short-circuited winding. The operating principle of an induction furnace is as follows:

• using a generator, an alternating current is created in the inductor;
• an inductor with a capacitor creates an oscillatory circuit, it is tuned to the operating frequency;
• in the case of using a self-oscillating generator, the capacitor is excluded from the device circuit and in this case the inductor’s own reserve capacitance is used;
• the magnetic field created by the inductor can exist in free space or be closed using an individual ferromagnetic core;
• the magnetic field acts on the metal workpiece or charge located in the inductor and forms a magnetic flux;
• according to Maxwell's equations, it induces a secondary current in the workpiece;
• with a solid and massive magnetic flux, the created current is closed in the workpiece and a Foucault current or eddy current is created;
• after the formation of such a current, the Joule-Lenz law comes into effect, and the energy obtained using an inductor and a magnetic field heats the metal workpiece or charge.

Despite multi-stage operation, the induction furnace device can provide up to 100% efficiency in vacuum or air. If the medium has magnetic permeability, then this indicator will increase; in the case of a medium made of a non-ideal dielectric, it will fall.

Device

The furnace in question is a kind of transformer, but it does not have a secondary winding; it is replaced by a metal sample placed in the inductor. It will conduct current, but the dielectrics do not heat up in this process, they remain cold.

The design of induction crucible furnaces includes an inductor, which consists of several turns of a copper tube, coiled in the form of a coil, with coolant constantly moving inside it. The inductor also contains a crucible, which can be made of graphite, steel and other materials.

In addition to the inductor, the furnace has a magnetic core and a hearth stone, all of which are enclosed in the furnace body. It includes:

In high-power furnace models, the bath casing is usually made quite rigid, so there is no frame in such a device. The housing fastening must withstand strong loads when the entire oven is tilted. The frame is most often made of shaped beams made of steel.

A crucible induction furnace for melting metal is installed on a foundation into which supports are mounted; the axles of the tilting mechanism of the device rest on their bearings.

The bath casing is made from metal sheets, onto which stiffeners are welded for strength.

The induction unit casing is used as a connecting link between the furnace transformer and the hearth stone. To reduce current losses, it is made of two halves, between which there is an insulating gasket.

The halves are connected using bolts, washers and bushings. Such a casing is made cast or welded; when choosing a material for it, preference is given to non-magnetic alloys. The two-chamber induction steelmaking furnace comes with a common casing for both the bath and the induction unit.

IN small ovens, in which water cooling is not provided, there is ventilation unit, it helps remove excess heat from the unit. Even if you install a water-cooled inductor, you need to ventilate the opening near the hearth stone so that it does not overheat.

Modern furnace installations not only have a water-cooled inductor, but also provide water cooling of the casings. Fans powered by a drive motor can be installed on the furnace frame. If such a device has a significant mass, the ventilation device is installed near the stove. If an induction furnace for steel production comes with a removable version of induction units, then each of them is provided with its own fan.

Separately, it is worth noting the tilt mechanism, which for small ovens comes with a manual drive, and for large ovens it is equipped hydraulic drive located at the drain spout. Whatever the tilt mechanism is installed, it must ensure that the entire contents of the bathroom are completely drained.

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 sources, the calculation of an induction furnace begins with calculating the power of the unit.

The power of an 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 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 necessary to take into account the metal or alloy being melted: according to the condition, it is zinc. This is an important point, the heat balance of cast iron melting in an induction furnace, as well as other alloys, is different.

Useful power transferred to liquid metal:

• Рpol = Wtheor×t×P,
• Wtheor – specific energy consumption, it is theoretical, and shows the overheating of the metal by 1 0 C;
• P – productivity of the furnace installation, t/h;
• t is the overheating temperature of the alloy or metal billet in the furnace bath, 0 C
• Rpol = 0.298×800×5.5 = 1430.4 kW.

Active power:

• P = Ppol/Yuterm,
• Rpol – taken from the previous formula, kW;
• Yuterm is the efficiency of a foundry furnace, its limits are from 0.7 to 0.85, with an average of 0.76.
• P = 1311.2/0.76 = 1892.1 kW, the value is rounded to 1900 kW.

At the final stage, the inductor power is calculated:

• Rind = P/N,
• P – active power of the furnace installation, kW;
• N is the number of inductors provided on the furnace.
• Rind =1900/2= 950 kW.

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

Species and subspecies

Induction furnaces are divided into two main types:

In addition to this division, induction furnaces are compressor, vacuum, open and gas-filled.

DIY induction furnaces

Among the available common methods for creating such units can be found step by step guide How to make an induction furnace from a welding inverter, with a nichrome spiral or graphite brushes, we will give their features.

High frequency generator unit

It is performed taking into account the design power of the unit, eddy losses and hysteresis leaks. The structure will be powered from a regular 220 V network, but using a rectifier. This type of furnace can be equipped with graphite brushes or a nichrome spiral.

To create a furnace you will need:

• two UF4007 diodes;
• film capacitors;
• field-effect transistors, two pieces;
• 470 Ohm resistor;
• two throttle rings, they can be removed from an old computer system technician;
• copper wire Ø section 2 mm.

The tools used are a soldering iron and pliers.

Here is a diagram for an induction furnace:

Induction portable melting furnaces of this type are created in the following sequence:

1. Transistors are located on radiators. Due to the fact that during the process of metal melting the device circuit heats up quickly, the radiator for it must be selected with large parameters. It is permissible to install several transistors on one generator, but in this case they need to be isolated from the metal using gaskets made of plastic and rubber.
2. Two chokes are manufactured. For them, two rings previously removed from the computer are taken, copper wire is wound around them, the number of turns is limited from 7 to 15.
3. The capacitors are combined into a battery to produce a capacitance of 4.7 μF at the output; they are connected in parallel.
4. A copper wire is wrapped around the inductor; its diameter should be 2 mm. The inner diameter of the winding must match the size of the crucible used for the furnace. A total of 7-8 turns are made and long ends are left so that they can be connected to the circuit.
5. A 12 V battery is connected to the assembled circuit as a source; it lasts for about 40 minutes of oven operation.

If necessary, the housing is made of a material with high heat resistance. If an induction melting furnace is made from a welding inverter, then a protective housing must be present, but it must be grounded.

Graphite brush design

Such a furnace is used for smelting any metal and alloys.

To create a device you need to prepare:

• graphite brushes;
• powdered granite;
• transformer;
• fireclay brick;
• steel wire;
• thin aluminum.

The technology for assembling the structure is as follows:

Device with nichrome spiral

Such a device is used for smelting large volumes of metal.

As consumables for arrangement homemade stove used:

• nichrome;
• asbestos thread;
• piece of ceramic pipe.

After connecting all the components of the furnace according to the diagram, its operation is as follows: after applying electric current to the nichrome spiral, it transfers heat to the metal and melts it.

The creation of such a furnace is carried out in the following sequence:

This design is characterized by high performance; it cools down for a long time and heats up quickly. But it is necessary to take into account that if the spiral is poorly insulated, it will quickly burn out.

Prices for ready-made induction furnaces

Homemade furnace designs will cost much less than purchased ones, but they cannot be created in large volumes, so you cannot do without ready-made options for mass production of the melt.

Prices for induction furnaces for metal melting depend on their capacity and configuration.

Model	Characteristics and Features	Price, rubles
INDUTHERM MU-200	The furnace supports 16 temperature programs, the maximum heating temperature is 1400 0C, the mode is controlled with an S-type thermocouple. The unit produces a power of 3.5 kW.	820 thousand
INDUTHERM MU-900	The furnace operates from a power supply of 380 V, temperature control occurs using an S-type thermocouple and can reach up to 1500 0C. Power – 15 kW.	1.7 million
UPI-60-2	This mini induction melting furnace can be used for melting non-ferrous and precious metals. The workpieces are loaded into a graphite crucible, and they are heated according to the transformer principle.	125 thousand
IST-1/0.8 M5	The furnace inductor is a basket in which a magnetic circuit is built together with a coil. Unit 1 ton.	1.7 million
UI-25P	The furnace device is designed for a load of 20 kg, it is equipped with a geared inclination of the melting unit. The stove comes with a block of capacitor batteries. Installation power – 25 kW. Maximum heating t is 1600 0C.	470 thousand
UI-0.50T-400	The unit is designed for a load of 500 kg, the highest power of the installation is 525 kW, the voltage for it must be at least 380V, the maximum operating temperature is 1850 0C.	900 thousand
ST 10	The oven of the Italian company is equipped with a digital thermostat; SMD technology is built into the control panel, which is fast. The universal unit can work with different capacities from 1 to 3 kg, for this it does not need to be readjusted. It is intended for precious metals, its maximum temperature is 1250 0C.	1 million
ST 12	Static induction oven with digital thermostat. It can be supplemented with a vacuum casting chamber, which makes it possible to carry out casting right next to the installation. Control occurs using the touch panel. Maximum temperature– 1250 0С.	1050 thousand
IChT-10TN	The furnace is designed for a load of 10 tons, it is a rather voluminous unit, for its installation you need to allocate a closed workshop room.	8.9 million

Conclusion

Making an induction furnace yourself is exciting, but it comes with some limitations and unknown consequences, since you need to rely on the laws of physics and chemistry, and those who are not good at this will not be able to carry out the process safely. For frequent use of such a setup, it is better to choose suitable option from those presented above.

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Many people believe that the process of smelting metal requires huge structures, almost factories with a large number of personnel. But there is also such a profession as a jeweler and metals such as gold, silver, platinum and others, used to make openwork and exquisite jewelry, some of which are rightfully considered real works of art. A jewelry workshop is an enterprise that does not tolerate excessive scale. And the melting process is simply necessary in them. Therefore, an induction furnace for melting metal is necessary here. It is not big, and very effective, and easy to use.

The operating principle of an induction furnace is a wonderful example of how an undesirable phenomenon is used with increased efficiency. The so-called Foucault eddy induction currents, which usually interfere in any type of electrical engineering, are here aimed only at a positive result.

In order for the metal structure to begin to heat up and then melt, it must be placed under these very Foucault currents, and they are formed in an induction coil, rather than in by and large and is the oven.

Simply put, everyone knows that while working, any electrical appliance starts to heat up. An induction furnace for melting metal uses this otherwise undesirable effect to its full potential.

Advantages over other types of melting furnaces

Induction furnaces are not the only invention used for melting metals. There are also famous open-hearth furnaces, blast furnaces and other types. However, the stove we are considering has a number of undeniable advantages over all others.

• Furnaces operating on the induction principle can be quite compact, and their placement will not cause any difficulties.
• High melting speed. If other furnaces for melting metal require several hours just to heat up, an induction furnace copes with this several times faster.
• The efficiency is only slightly less than 100%.
• In terms of melt purity, the induction furnace confidently takes first place. In other devices, the workpiece prepared for melting is in direct contact with the heating element, which often leads to contamination. Foucault currents heat the workpiece from the inside, affecting the molecular structure of the metal, and no by-products enter it.

This last advantage is essential in jewelry, where the frequency of a material increases its value and uniqueness.

Furnace placement

Compact induction furnace, depending on size, can be floor-standing or tabletop. Whatever option you choose, there are a few basic rules for choosing a place to put it.

• Despite the simplicity of handling the stove, it is still an electrical device that requires compliance with safety measures. And the first thing that needs to be taken into account during installation is the presence of the correct power source that matches the device model.
• Possibility of high-quality grounding.
• Providing the installation with a water supply.
• Tabletop ovens require a stable base.
• But most importantly, nothing should interfere during work. Even if the melt is not too large in volume and mass, its temperature is more than 1000 degrees and accidentally splashing it out of the mold means causing very severe injury to yourself or someone nearby.

There is nothing to say about the fact that there should be no flammable or, especially, explosive materials near a working induction furnace. But a fire shield within walking distance is absolutely necessary.

Types of induction furnaces

Two types of induction furnaces are widely used: channel and crucible. They differ only in the method of working with them. In all other respects, including advantages, such melting furnaces are very similar. Let's consider each option separately:

• Channel furnace. The main advantage of this type is a continuous cycle. You can load a new portion of raw materials and unload already molten metal directly during heating. The only difficulty may arise during startup. The channel through which the liquid metal will be discharged from the furnace must be filled.
• Crucible furnace. Unlike the first option, each portion of metal will have to be loaded separately. That's the point. The raw material is placed in a heat-resistant crucible and placed inside the inductor. After the metal has melted, it is drained from the crucible and only then the next portion is loaded. This furnace is ideal for small workshops where large masses of molten raw materials are not required.

The main advantage of both options is the speed of production. However, the crucible furnace wins here too. In addition, it is quite possible to make it with your own hands in almost home conditions.

A homemade induction furnace is not fraught with any difficulties so that it cannot be assembled a common person, at least a little familiar with electrical engineering. It has only three main blocks:

• Generator.
• Inductor.
• Crucible.

The inductor is a copper winding that you can make yourself. You will have to look for the crucible either in the appropriate stores or get it in other ways. And the following can be used as a generator: a welding inverter, a self-assembled transistor or lamp circuit.

Induction furnace on a welding inverter

The simplest and most widespread option. Efforts will have to be expended only on the construction of the inductor. Take a thin-walled copper tube 8-10 cm in diameter and bend it according to the desired pattern. The turns should be spaced at a distance of 5-8 mm, and their number depends on the characteristics and diameter of the inverter. The inductor is fixed in a textolite or graphite case, and a crucible is placed inside the installation.

Transistor induction furnace

In this case, you will have to work not only with your hands, but also with your head. And run around the shops looking for the necessary spare parts. After all, you will need transistors of different capacities, a couple of diodes, resistors, film capacitors, two copper wires of different thicknesses and a couple of inductor rings.

• Before assembly, it is necessary to take into account that the resulting circuit will become very hot during operation. Therefore it is necessary to use fairly large radiators.
• Capacitors are assembled in parallel into a battery.
• Copper wire with a diameter of 1.2 mm is wound onto the throttle rings. Depending on the power, the turns should be from 7 to 15.
• A cylindrical object, suitable in diameter to the size of the crucible, is wound with 7-8 turns of copper wire with a diameter of 2 mm. The ends of the wire are left long enough for connection.
• According to a special scheme, everything is mounted on the board.
• The power source can be a 12-volt battery.
• If necessary, you can make a textolite or graphite case.
• The power of the device is adjusted by increasing or decreasing the turns of the inductor winding.

Assembling such a device yourself is not easy. And you can take on this work only if you are confident in the correctness of your actions.

Induction furnace with lamps

Unlike a transistor oven, a lamp oven will be much more powerful, which means you will have to handle both it and the circuit more carefully.

• 4 beam lamps connected in parallel will generate high frequency currents.
• Copper wire is bent into a spiral. The distance between the turns is 5 or more millimeters. The coils themselves are 8-16 cm in diameter. The inductor should be of such a size that the crucible can easily fit inside.
• The inductor is placed in a housing made of a non-conducting material (textolite, graphite).
• You can put a neon indicator lamp on the body.
• You can also include a tuning capacitor in the circuit.

Making both circuits requires having some knowledge, which can be obtained, but it is better if a real specialist does it.

Cooling

This question is probably the most difficult of all those that are posed to a person who decides to independently assemble a melting apparatus based on the induction principle. The fact is that it is not recommended to place the fan directly next to the stove. Metal and electrical parts of the cooling device can adversely affect the operation of the stove. A fan located far away may not provide the necessary cooling, which will lead to overheating.

The second option is to carry out water cooling. However, performing it efficiently and correctly at home is not only difficult, but also not financially profitable. In this case, it’s worth thinking about: wouldn’t it be more economical to purchase an industrial version of an induction furnace, produced at a factory, in compliance with all the necessary technologies?

Safety precautions when smelting metal in an induction furnace

There is no need to dwell heavily on this topic, since almost everyone knows the basic safety regulations. We should dwell only on those issues that are unique to this type of equipment.

• Let's start with personal safety. When working with an induction furnace, you should be well aware that the temperatures here are very high, and this poses a risk of burns. The device is also electric and requires special attention.
• If you bought a finished stove, you should pay attention to the radius of influence of the electromagnetic field. Otherwise, watches, phones, video cameras and other electronic gadgets may begin to malfunction or even break down completely.
• Work clothes should be selected with non-metallic fasteners. Their presence, on the contrary, will affect the operation of the furnace.
• Particular attention should be paid to the lamp oven in this regard. All high voltage elements must be hidden in the housing.

Of course, such equipment is unlikely to be useful in a city apartment, but radio amateurs who are constantly engaged in tinning and jewelry makers cannot do without an induction stove. For them, this thing is very useful, one might say irreplaceable, and how it helps in their work, it is better to ask them themselves.