Schematic diagram of household induction electric stoves. The principle of operation of the induction cooker

For melting metal on a small scale, some kind of device is sometimes necessary. This is especially acute in the workshop or in small production. The most effective at the moment is a furnace for melting metal with an electric heater, namely induction. Due to the peculiarity of its structure, it can be effectively used in blacksmithing and become an indispensable tool in the forge.

Induction furnace device

The oven consists of 3 elements:

1. Electronic-electrical part.
2. Inductor and crucible.
3. inductor cooling system.

In order to assemble an operating furnace for melting metal, it is enough to assemble a working electrical circuit and an inductor cooling system. The easiest option for melting metal is shown in the video below. Melting is performed in the counter electromagnetic field of the inductor, which interacts with the induced electro-eddy currents in the metal, which keeps a piece of aluminum in the space of the inductor.

In order to effectively melt the metal, currents of large magnitude and high frequency of the order of 400-600 Hz are required. The voltage from an ordinary 220V household outlet has sufficient data to melt metals. It is only necessary to turn 50 Hz into 400-600 Hz.
Any scheme for creating a Tesla coil is suitable for this.

Tins and other scrap - for recycling! How to make a do-it-yourself aluminum melting furnace

I liked the following 2 schemes on the lamp GU 80, GU 81 (M). And powering the lamp with an ILO transformer from a microwave.

These circuits are designed for a Tesla coil, but an induction furnace is excellent from them; instead of the secondary coil L2, it is enough to place a piece of iron in the interior of the primary winding L1.

The primary coil L1 or inductor consists of a copper tube rolled into 5-6 turns, at the ends of which a thread is cut to connect the cooling system. For levitational melting, the last turn should be done in the opposite direction.
Capacitor C2 on the first circuit and identical to it on the second sets the frequency of the generator. At a value of 1000 pF, the frequency is about 400 kHz. This capacitor must be high-frequency ceramic and designed for high voltage of the order of 10 kV (KVI-2, KVI-3, K15U-1), other types are not suitable! Better to put K15U. You can connect capacitors in parallel. It is also worth considering the power for which the capacitors are designed (this is written on the case), take it with a margin. the other two capacitors KVI-3 and KVI-2 heat up during prolonged operation. All other capacitors are also taken from the KVI-2, KVI-3, K15U-1 series, only the capacitance changes in the characteristics of the capacitors.
Here's a schematic of what it should look like. Framed 3 blocks.

The cooling system is made of a pump with a flow of 60 l / min, a radiator from any VAZ car, and I put a regular home cooling fan in front of the radiator.

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Masters of their craft: we make a melting furnace

A smelting furnace is a large or portable facility in which some non-ferrous metal can be melted. The induction melting furnace is widely known. In industrial conditions, for melting metal in large quantities, induction melting furnaces of considerable size are installed in special rooms. They melt metal, from which many parts for motorcycles, cars, tractors are cast. To melt up to 5 kg of aluminum. you can build your own induction melting furnaces, solid fuel, gas installations. They all work great. How and from what can you make a home melter?

We build our own furnace for melting

The installation for melting metal (Fig. 1) is assembled from bricks. It must be fireproof. Chamotte clay is used as a binder. To burn the device with coal, forced air is needed. For it, in the lower half of the unit, it is necessary to leave a special channel for air access. A grate is placed under this channel. This is a special cast-iron grate on which coal or coke is laid out. The grate can be used from an old stove or purchased on the market, in a hardware store. For strength, some scald the finished structure with a metal belt. Brick can be placed on edge.

A melting furnace cannot do without a crucible. Instead, you can use a cast-iron cauldron. It can be found on the farm. Well, if it turns out to be enameled. The crucible is placed closer to the burning coke. It remains to put a fan as a forced blower, light the coke and start melting. Do-it-yourself oven is ready. It can be used for melting cast iron, copper, bronze, aluminum.

Construction of a tabletop oven

From simple materials, you can build gas or electric devices that fit perfectly on a table or workbench. For work you will need:

Asbestos has been banned for domestic use in recent years, so it can be replaced with tile or cement tiles. Dimensions depend on the desire of the owner. An important role here is played by the power of the electrical network and the output voltage of the transformer. It is enough to apply a voltage of 25 V to the electrodes. For an industrial transformer used in welding, this voltage is usually 50-60 V. In this case, the distance between the electrodes must be increased. Much is done by experience. As a result, melting 60-80 g of metal is a good result.

Electrodes are best made from brushes from a fairly powerful electric motor. They have a very handy power cord. You can carve them yourself. There should be no big problems with finding material. In a home-made product, you need to drill holes with a diameter of 5-6 mm on the side, insert a copper stranded wire with a thickness of about 5 mm into them, carefully hammer in a nail to secure the wire. It remains to make a notch with a file, it will help to improve contact with graphite in powder form. Inside the furnace is laid out with mica. This is an excellent thermal insulator. Outside, the walls of the furnace are reinforced with tiles.

To power the furnace, you can take a transformer that lowers the mains voltage to 52 V. The mains winding is wound with 620 turns of wire Ø1 mm. The lowering winding is wound with a 4.2x2.8 mm wire with fiberglass insulation. Number of turns #8212; 70. The furnace is connected to the transformer with wires with a cross section of 7-8 mm² in good insulation. The finished installation must be turned on for a while so that all organic inclusions burn out. The stove is assembled by hand.

using a scoop or spatula, pour graphite and make a hole in it;
a material blank is laid in the hole;
precious metals must be placed in a glass ampoule;
tin and aluminum are placed in a separate iron cup;
for alloys, refractory metal is melted first, then low-melting metal.

It is impossible to melt magnesium, zinc, cadmium, silver contacts in such furnaces.

When melted, cadmium burns out with the formation of poisonous yellow smoke.

When working with the installation, you must observe safety precautions:

Do not allow short circuits in the wires.
The mains switch must be located near the operator.
Do not leave the device unattended during operation.
Nearby there is always a container in which water is poured, in which the workpieces are cooled.
For melting cast iron and other metals, goggles and gloves must be used.

If desired, gas installations can be made. They are well suited for melting small batches of non-ferrous metal. Induction furnaces for melting are capable of melting any metals. They can be used as conventional installations for working with non-ferrous and precious metals, as melting holding furnaces in production. They are suitable for various needs: for heating metals, for the manufacture of alloys of several metals, for the smelting of cast iron.

You can melt a small piece of iron in a self-assembled induction furnace. This is the most efficient device that runs on a 220V home outlet. The oven is useful in the garage or workshop, where it can be placed simply on the desktop. It makes no sense to buy it, since a do-it-yourself induction furnace is assembled in a couple of hours if a person can read electrical circuits. It is undesirable to do without a diagram, because it gives a complete picture of the device and allows you to avoid connection errors.

Scheme of the induction furnace

Parameters of the induction furnace

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How to properly assemble an induction furnace?

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Plates of Russian and imported production are presented, which do not change for years.
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The main elements and units of the stove: heating element E1 (in the first burner), E2 (in the second burner), E3-E5 (in the oven), a switching unit consisting of switches S1-S4, thermal relay F type T-300, indicators HL1 and HL (gas-discharge to indicate the operation of the heating element), HL3 (incandescent type to illuminate the oven). The power of each heating element is about 1 kW

A 4-position switch S1 is used to adjust the power and degree of heating of the heating element of the oven. When its handle is set to the first position, contacts P1-2 and P2-3 will close. At the same time, the following will be connected to the network using a plug: TEN E3 in series with parallel connected TEN E2 and E3. The current will pass along the path: the lower contact of the XP, F, P1-2, E4 and E5, E3, P2-3, upper HR plug contact. Since the E3 heater is connected to the E4 and E5 heaters in series, the 38 circuit resistance will be maximum, and the power and degree of heating will be minimal. In addition, the neon indicator HL1 will glow due to the passage of current through the circuit: the lower contact of the plug XP, F, P1-2, E4 and E5, R1, HL1, the upper contact XP.

Connecting nodes Dream 8:

In the second position, contacts P1-1, P2-3 are switched on. In this case, the current will flow through the circuit: the lower contact of the plug XP, F, P1-1, E3, P2-3, the upper contact XP. In this situation, only one E3 heating element will work and the power will be greater due to a decrease in the total resistance at a constant mains voltage of 220V.

In the third position of the switch S1, the contacts P1-1, P2-2 will close, which will lead to the connection to the network of only parallel connected heating elements E4 and E5. Switch S4 is used to turn on the oven light HL3.

5.Elektra 1002

H1, H2 - tubular burners, H3 - cast iron burner 200mm, H4 - cast iron burner 145mm, P1, P2-stepless power controls, P3, P4-seven-position power switches, PSH - three-stage oven switch, P5-blocking switch, L1 .... L4 - signal lamps for turning on the burners, L5 - signal lamp for turning on the heaters of the oven or grill, L6 - signal lamp for reaching the set temperature in the oven, H5, H6 - heaters for the oven, H7 - grill, T - thermostat, B - key switch, L7 - oven lighting lamp, M - motor reducer.

6. BURNER SWITCHES Combustion, Hansa, Elektra, Lysva:

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Table of contents:

Principle of operation
Parameters of the induction furnace
Features of the operation of the inductor

You can melt a small piece of iron in a self-assembled induction furnace.

How to make a crucible or melting furnace with your own hands

This is the most efficient device that runs on a 220V home outlet. The oven is useful in the garage or workshop, where it can be placed simply on the desktop. It makes no sense to buy it, since a do-it-yourself induction furnace is assembled in a couple of hours if a person can read electrical circuits. It is undesirable to do without a scheme, because it gives a complete picture of the device and allows you to avoid connection errors.

The principle of operation of the induction furnace

A home-made induction furnace for melting a small amount of metal does not require large dimensions and such a complex device as industrial units. Its work is based on the generation of current by an alternating magnetic field. The metal is melted in a special blank called a crucible and placed in an inductor. It is a spiral with a small number of turns of a conductor, such as a copper tube. If the device is used for a short time, the conductor will not overheat. In such cases, it is sufficient to use copper wire.

A special generator launches powerful currents into this spiral (inductor), and an electromagnetic field is created around it. This field in the crucible and in the metal placed in it creates eddy currents. It is they who heat the crucible and melt the metal due to the fact that it absorbs them. It should be noted that the processes occur very quickly if a non-metal crucible is used, for example, fireclay, graphite, quartzite. A home-made melting furnace provides for a removable crucible design, that is, metal is placed in it, and after heating or melting, it is pulled out of the inductor.

Scheme of the induction furnace

The high frequency generator is assembled from 4 electron tubes (tetrodes), which are connected in parallel. The heating rate of the inductor is controlled by a variable capacitor. Its handle is brought out and allows you to adjust the capacitance of the capacitor. The maximum value will provide heating of a piece of metal in the coil in just a few seconds to a red state.

Parameters of the induction furnace

The effective operation of this device depends on the following parameters:

generator power and frequency,
the amount of eddy current losses,
the rate of heat loss and the amount of these losses to the surrounding air.

How to choose the components of the circuit in order to obtain sufficient conditions for melting in the workshop? The generator frequency is pre-set: it should be 27.12 MHz if the device is assembled by hand for use in a home workshop. The coil is made of a thin copper tube or wire, PEV 0.8. It is enough to make no more than 10 turns.

Electronic lamps should be used with high power, for example, brand 6p3s. The scheme also provides for the installation of an additional neon lamp. It will serve as an indicator of device readiness. The circuit also provides for the use of ceramic capacitors (from 1500V) and chokes. Connection to a home outlet is carried out through a rectifier.

Externally, a home-made induction furnace looks like this: a generator with all the details of the circuit is attached to a small stand with legs. An inductor (spiral) is connected to it. It should be noted that this assembly option for a home-made melting device is applicable for working with a small amount of metal. The inductor in the form of a spiral is the easiest to make, therefore, for a home-made device, it is used in this form.

Features of the operation of the inductor

However, there are many different modifications of the inductor. For example, it can be made in the shape of a figure eight, trefoil, or any other shape. It should be convenient for placing material for heat treatment. For example, a flat surface is easiest to heat with serpentine coils.

In addition, it tends to burn through, and in order to extend the life of the inductor, it can be insulated with heat-resistant material. Use, for example, filling with a refractory mixture. It should be noted that this device is not limited to copper wire material. You can also use steel wire or michrome. When working with an induction furnace, its thermal hazard must be taken into account. If accidentally touched, the skin gets a severe burn.

Homemade melting crucible electric furnace.

So, a furnace for melting metal. Here I did not invent anything much, but simply tried to make a device, if possible from ready-made components and, if possible, without giving any slack in the manufacturing process.
At the furnace, the upper part is called the melter, the lower part is the control unit.
Don't let the white box on the right scare you - this is, in general, an ordinary transformer.
The main parameters of the furnace:
– furnace power - 1000 W
– crucible volume - 62 cm3
– maximum temperature - 1200 grC

smelter

Since my task was not to waste time on experiments with corundum-phosphate binders, but to save time by using ready-made components, I used a ready-made heater from YASAM, as well as a ceramic muffle working with it.

Heater: Fechral, wire diameter 1.5 mm, rods 3 mm in diameter are welded to the terminals. Resistance 5 ohm. The presence of a muffle is mandatory, since the wires inside the heater are bare. Heater size Ф60/50х124 mm. Muffle dimensions Ф54.5/34х130 mm. In the bottom of the muffle we make a hole for the elevator rod.
The body of the melter is made of standard stainless steel. 220/200 pipe machined to an acceptable wall thickness. The height is also taken for a reason. Since we will have a fireclay brick as a lining, the height is taken taking into account three brick thicknesses. It's time to post the assembly drawing. In order not to clutter up the page, I will not publish here, but I will give links: Part1, Part2.
The first drawing does not show the lightweight fireclay washer on which the crucible rests, the height of the washer depends on the crucible used. There is a hole for the rod in the center of the washer. The rod is pointed and in the lower position does not reach the crucible.
As I already wrote, the lining of the furnace is made of fireclay lightweight bricks ШЛ 0.4 or ШЛ 0.6 of size No. 5. Its dimensions are 230x115x65 mm. Brick is easily processed with saws and sandpaper. Saws, however, will not last long 🙂 Fireclay brick processing. On the right is the original brick 🙂
Rectilinear cuts - a hacksaw for wood, for curved cuts - a home-made saw from a hacksaw blade with large teeth, with a reduced (grinded) blade width.

In the manufacture of lining, simple rules should be observed:
- do not use any mortar to hold the parts together. Everything is dry. It still breaks
— parts of the lining should not abut anywhere. There must be slack, gaps
- large parts of the lining, if you make it from another material, it is better to divide it into small parts. It will still split. Therefore, you better do it.

For the thermocouple in the third layer we make a hole, and in the second and first layers we make a gap between the heater and the lining. The gap is such that the thermocouple is pushed in tightly, as close as possible to the heater. You can use a purchased thermocouple in the same place in YASAM, but I use homemade ones. It's not that I feel sorry for the money (although they are quite expensive there), I just basically leave a bare junction for better thermal contact. Although there is a risk of burning the input circuits of the regulator.

Control block

In the control unit, the lower and upper covers are equipped with grilles for cooling the heater leads. All the same, the diameter of the pins is 3 mm. In addition, heat radiation through the bottom of the melter is also present. The regulator does not need to be cooled - 10 watts in total. At the same time, cool the cold ends of the thermocouple. Control unit with temperature controller Termodat-10K2. Top right is the on/off switch. At the top left is the crucible lift lever with the lift rod (stainless steel electrode Ф3mm).

Why I chose Termodat as a regulator. I dealt with Aries, but after one winter in an unheated room, his firmware crashed. The thermodat has withstood several winters and has retained not only the firmware, but also the settings.

Crucible furnace: design options, do-it-yourself manufacturing

In addition, the case is metal, indestructible. (We should at least take a bubble from Permians, for advertising 🙂
In addition, they can also take a power element - the Triac Control Unit BUS1-V01. This block is designed to work with Thermodata.
The instruction for Termodat-10K2 is here.

Diagram of an electric oven. The thick line shows high-current circuits. They use a wire of at least 6 mm2.

I'll talk about the transformer later. Now about the control unit. It is turned on by the T1 toggle switch, protected by a 0.25 A fuse. In addition, a line filter is provided to power the regulator, which is located in the transformer housing. A triac TS142-80 (1420 volts, 80 amperes, ordered in CHIP and DIP) is used as a power element. I put the triac on a radiator, but as practice has shown, it almost does not heat up. Do not forget to isolate the triac from the case. Or mica, or ceramics. Either the triac itself, or assembled with a radiator.

In the photo, behind the Thermodat, there is a fan power supply. I then added it to the fan, which I placed on the lower grille. The power supply unit is the simplest - trans, bridge and capacitor, produces 12 volts. Computer fan.
Heater outlet. Through the grate output in a ceramic tube. To connect to the terminal, I used a bolt drilled across.
Entering a thermocouple into the control unit. If you do not have such a ceramic tube, send the required amount to YaSAM.

Please note - the installation is made with an ordinary mounting wire, high-current circuits - stranded at least 6 mm2, thermocouple ends - directly into the terminal block. BUS in the factory form does not fit, I had to remove the cover - (and who is easy now? ;). The rest can be seen in the photo.

Transformer.

Despite such a formidable appearance, this device is a conventional 1 kW transformer. It's just that before that he changed several professions (graphite smelter, welder, etc.) and got a case, an automatic switch, an indicator of the current consumed from the network, and other wonderful things.

Of course, you do not have to fence all this, a simple kilowatt trance under the table is enough. The basis of everything is a sh-shaped iron transformer. I, depending on the need, rewind it without disassembling and without changing the primary.
What is a transformer for? The fact is that in order for the heater to work for some acceptable amount of time, the diameter of the wire must be as thick as possible. After analyzing this table, we can draw a disappointing conclusion - the wire should be as thick as possible. And this is no longer 220 volts.

Therefore, you will not find heaters designed for 220 volts in serious devices. Directly, if you connect this heater to the network, then the power consumption will be around 9 kW. You will plant a network throughout the house, and such a blow will be fatal for the heater. Therefore, voltage limiting circuits are used. For me, the most convenient is to use a transformer.
So, the primary: - 1.1 Volts per turn
- No-load current 450 mA
Secondary: - for a load of 5 ohms and a power of 1000 W, the voltage will be 70 Volts
- secondary current 14 A, wire 6 mm2, wire length 28 m.
Of course, this heater is not eternal. But I can replace it by finding a suitable wire and quickly rewinding the secondary.
If you read the instructions for Thermodat, then there is the possibility of limiting the maximum power. But this will not work for us, because we are talking about the average power per heater. In the mode of distributed pulses, as we have, the pulses will be for all 9 kW and we risk getting a pandemonium with light music. And on the neighbors too, because the machines in the entrance are also designed for average power.

For those who do not like to read instructions for a long time, I post a cheat sheet with coefficients and settings for a specific oven. After setting the Thermodata, turn on the trance and go.
The indicator of the current consumed from the network, due to the inertia of the arrow, also shows the average power. While the heater is cold, the current will be closer to 5 amps, as it warms up a little lower (due to the increase in heater resistance). As it approaches the setpoint, it will drop to almost zero (PID operation).

We load a full crucible with bronze scrap, close the lid. The lid is lined from the inside with fireclay lightweight on a mortar for fireplaces and stoves. For those who are especially curious (I myself am), there is a window covered with mica in the lid.

The temperature is over 1000, and the surface of the melter has not yet warmed up. This speaks volumes about the quality of the lining. After 30-40 minutes, the contents of the crucible melted.
After the end of melting, we press the elevator lever, after which we can already pick up the crucible with a grip. The photo shows a recess in the upper part of the crucible just for a secure grip.

P.S. About crucibles. YaSAM completes its furnaces with graphite crucibles that work with these heaters. If you work with gold and silver, it makes sense to buy them. But I am against these bourgeois excesses. The fact is that the F32/28 stainless pipe miraculously coincides with the diameter of the graphite crucible. Draw your own conclusion

We isolate the heater leads from the body with ceramic tubes. Ceramic tubes - from fuses, it is possible from resistors.

The top row of bricks is flush with the edge of the hull. Don't forget the hole for the elevator rod.

Third layer of lining. In this layer we make holes for the heater leads and for the thermocouple (pictured).

The second layer of lining. Cut for the upper output of the heater.

In induction furnaces, the metal is heated by currents excited in the non-variable field of the inductor. In essence, induction furnaces are also resistance furnaces, but differ from them in the way that energy is transferred to the heated metal. Unlike resistance furnaces, electrical energy in induction furnaces is first converted into electromagnetic energy, then again into electrical energy, and finally into thermal energy.

With induction heating, heat is released directly in the heated metal, so the use of heat is the most complete. From this point of view, these furnaces are the most advanced type of electric furnaces.

There are two types of induction furnaces: with a core and without a core, crucible. In core furnaces, the metal is in an annular trough around the inductor, inside of which the core passes. In crucible furnaces, a crucible with metal is located inside the inductor. It is impossible to use a closed core in this case.

Due to a number of electrodynamic effects that occur in the metal ring around the inductor, the specific power of channel furnaces is limited to certain limits. Therefore, these furnaces are mainly used for melting low-melting non-ferrous metals and only in some cases are used for melting and overheating cast iron in foundries.

The specific power of induction crucible furnaces can be quite high, and the forces resulting from the interaction of metal and inductor magnetic furnaces have a positive effect on the process in these furnaces, contributing to metal mixing.

How to assemble an induction furnace - diagrams and instructions

Coreless induction furnaces are used for smelting special, especially low-carbon steels and alloys based on nickel, chromium, iron, cobalt.

An important advantage of crucible furnaces is the simplicity of design and small dimensions. Thanks to this, they can be completely placed in a vacuum chamber and it is possible to process the metal with vacuum during the melting process. As vacuum steel-smelting units, induction crucible furnaces are becoming more and more widespread in the metallurgy of high-quality steels.

Figure 3. Schematic representation of an induction channel furnace (a) and a transformer (b)

Induction furnaces. Melting technology in induction furnaces

INDUCTION CRUCIBLE FURNACES.

Alloys of ferrous and non-ferrous metals and pure Me (cast iron, steel, bronze, brass, copper, and aluminum) are smelted in these furnaces. By current frequency: 1) Furnaces of industrial frequency 50 Hz. 2) Medium frequency up to 600 Hz. (up to 2400 Hz also included). 3) High frequency up to 18000Hz.

Often ind. ovens work in pairs (duplex process). In the first furnace, the mixture is melted, in the second, Me is brought to the desired chemical. composition or withstand Me at the desired t-re until the moment of pouring. The transfer of Mel from furnace to furnace can be carried out continuously along the chute using crane ladles or ladles on an electric car. In induction furnaces, the composition of the charge changes, instead of pig iron, lightweight low-quality materials are used (shavings, lightweight scrap metal, waste from own production, i.e. trimmings).

Operating principle The charge is loaded into the crucible, variable el. the current passing through the inductor (coil) creates a magnetic field that induces an electromotive force in the metal cage, which is caused by induced currents, which cause heating and melting of Mel. Inside the coil there is a crucible made of refractory material, which protects the inductor from exposure to liquid Mel. The primary winding is an inductor. Secondary winding and at the same time load - Me-l in the crucible.

The efficiency of the furnace depends on the electrical resistance of Me-la and on the frequency of the current. For high efficiency, it is necessary that the diameter of the charge (d of the crucible) be at least 3.5-7 depths of current penetration in Me-l. Approximate ratios between the crucible capacity and the current frequency for steel and cast iron. The productivity of the furnaces is usually 30-40 t/h for cast iron and steel. With an electric power consumption of 500-1000 kWh / ton. For bronze, copper 15-22 t/h, for aluminum 8-9 t/h. Most often, a cylindrical crucible is used. The magnetic flux created by the inductor passes through closed lines both inside the inductor and outside.

Depending on the way the magnetic flux passes from the outside, there are: 1) open; 2) shielded; 3) closed oven design

With an open design, the magnetic flux passes through the air, so the structural elements (for example, the frame) are non-metallic or placed at a great distance from the inductor. When shielding, the magnetic flux from steel structures is separated by a copper screen. When closed - the magnetic flux passes through the radially arranged packages of transformer steel - magnetic circuits.

Scheme of the device of an electric induction furnace: 1 - cover, 2 turning unit, 3 - inductor, 4 - magnetic circuits, 5 - metal structure, 6 - water cooling inlets, 7 - crucible, 8 - platform

The furnace includes sl. nodes:Inductor, Lining, Frame, Magnetic circuits, Cover, Padina, Tilt mechanisms.

Aluminum Smelting Furnace

In addition to the main purpose, the inductor also performs the function of the element that perceives the fur. and thermal load from the crucible. In addition, the cooling of the inductor ensures the removal of heat that occurs due to electrical losses, therefore, the inductors are made either in the form of a cylindrical single-layer coil, where all the turns are arranged in the form of a spiral with a constant angle of inclination, or in the form of a coil, all the turns of which are laid in a horizontal plane , and the transitions between them are in the form of short inclined sections.

Depending on the Me-la brand and the t-r level, 3 types of lining are used:

1. Sour(contains > 90% SiO2) withstands 80-100 melts

2. Main(up to 85% MgO) withstands 40-50 melts for small furnaces and up to 20 melts for furnaces with a capacity of >1 ton

3. Neutral(based on Al2O3 or CrO2 oxides)

Schemes of induction melting furnaces: a - crucible, b - channel; 1 - inductor; 2 - molten metal; 3 - crucible; 4 - magnetic core; 5 - a hearth stone with a heat release channel.

The padina is made of fireclay bricks for large ovens or aspot cement for small ones. Issue cover from structural steel and lined from the inside. Advantages of crucible furnaces:1) Intensive circulation of the melt in the crucible; 2) The ability to create an atmosphere of any type (oxidizing, reducing, neutral) at any pressure; 3) High performance; 4) Possibility of complete draining of Me-la from the furnace; 5) Ease of maintenance, the possibility of mechanization and automation. Flaws: 1) Relatively low t-ra of slags induced on the Me-la mirror; 2) Relatively low durability of the lining at high melt t-p and in the presence of heat cycles.

INDUCTION DUCT FURNACES.

The principle of operation is that a variable magnetic flux permeates a closed circuit formed by liquid Chalk and excites a current in this circuit.

The contour of liquid Me-la is surrounded by a refractory material, which is baked into a steel case. The space filled with liquid Chalk has the shape of a curved channel. The working space of the furnace (bath) is connected to the channel by 2 holes, due to which a closed circuit is formed. During operation of the furnace, liquid Me-l moves in the channel and at the junctions with the bath. The movement is caused by Mel-la overheating (in the channel it is 50-100 ºС higher than in the bath), as well as by the influence of a magnetic field.

When all Mel is drained from the furnace, an electrical circuit breaks, which is created by liquid Mel in the channel. Therefore, in channel furnaces produce a partial discharge of liquid Me-la. The mass of the "swamp" is determined based on the fact that the mass of the column of liquid Mel above the channel exceeds the electrodynamic force pushing Mel out of the channel.

Channel furnaces are used as a mixer for holding and melting furnaces. The mixer is designed to accumulate a certain mass of Me-la and hold Me-la at a certain t-re. The capacity of the mixer is assumed to be at least twice the hourly output of the melting furnace. Dispensing ovens are used to pour liquid Me-la directly into molds.

Compared to crucible furnaces, channel furnaces have lower capital investments (50-70% of crucible furnaces), low specific power consumption (higher efficiency). Flaw: Lack of flexibility in chemical composition regulation.

The main nodes include: Furnace frame; lining; Inductor; Fur-zm tilt; Electrical equipment; Water cooling system.

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

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

The following devices can be made independently:

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

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

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

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

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

Manufacturing instructions

Blueprints

Figure 1. Electrical diagram of the induction heater

Figure 2. Device.

Figure 3. Scheme of a simple induction heater

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

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

Additional materials and their features:

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

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

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

Nuances

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

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

So I give everyone an example of both China and the West ..
While I had a welder over 40 kg, the counter did not hold well and the plugs flew out, I could not transport it without a car, and my navel tore for transfer, I dreamed of small devices and welding aluminum with an ordinary welder. And all smart electronic engineers did not shake their brains, and referred to smart formulas.
But then the West poured in, followed by China .. And the Miracles began!!! And now the LED lamp gives approximately the same luminous flux, but takes 10 times less electricity. Welding machines are almost 20 times lighter!!! I now have such an inverter 2.5 kg, it works with electrodes from 1 mm2 to 4 mm2 in cross section, and it consumes three times less electricity. And I don't care about the laws of J. Lenz, or whatever they are. I got more economical, practical, profitable products and tools. And that means it works, in spite of our smart people and smart girls from the 17th century !!! I personally need practical things that save my budget. And, by the way, in terms of heating and the power of these heaters .. they came up with MONOPOLIES from the Government those formulas that did not exist under the system of supply and distribution and the State Construction of the USSR. Then the power of paid thermal energy was calculated and paid for by the output power of each section of the heating battery, which was also measured in Gcal. I worked in the supply chain and dealt with a range of over 10,000 items. And therefore, I’m just fooling from the fact that now they don’t consider it from the hot water flowing per unit time, and the difference in temperature loss at the inlet at the outlet, but they count it by kW per 1 m2 instead of 1 kW of one section of a cast-iron or aluminum battery, and refer to convection heat walls, ceilings, and other load-bearing structures. It seems that these carriers also emit heat, which also needs to be taken into account when consuming the coolant. But not by the sensor on the section, and not by the volume of the passed coolant per unit of time. Namely, these units should consider the cost of money for the production and return of this heat. But who will check it at the Government level?? He needs to collect more money from the population through the monopolies of Lukoil and other resource companies. That is why these few calculation norms have been introduced for calculating payment from the population, which includes smart debaters. And therefore, smart people who believe who are on 1 m2, then on the induction of the walls .. please, it’s better to be silent.
This fee is for the Owner's heating costs when choosing a heater. It needs to be covered, and not to show knowledge of the THEORY of the 17-19 centuries ...
Look outside, and look at the Calendar. Now is the 2nd decade of the 21st century. And the satellites from Venus are returning .. And you are sitting there, on the heating elements ... Well, you are sitting. I choose Induction heating and water heater. My pension says so.

For many years, people have been smelting metal. Each material has its own melting point, which can be reached only with the use of special equipment. The first furnaces for melting metal were quite large and were installed exclusively in the workshops of large organizations. Today, a modern induction furnace can be installed in small workshops when setting up the production of jewelry. It is small, easy to handle and highly efficient.

Operating principle

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

Drain pump.
Water cooled inductor.
Frame in stainless steel or aluminium.
Contact area.
Hearth made of heat-resistant concrete.
Support with hydraulic cylinder and bearing unit.

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

Device advantages

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

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

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

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

Only two types of furnaces are widely used: crucible and channel. They have similar advantages and disadvantages, the differences are only in the method of work used:

The crucible variety of induction furnaces is more popular. This is due to their high performance and ease of operation. In addition, a similar design, if necessary, can be made independently.

Homemade versions are quite common.. To create them you need:

Generator.
Crucible.
Inductor.

An experienced electrician, if necessary, can make an inductor with his own hands. This structural element is represented by a winding of copper wire. The crucible can be purchased at the store, but a lamp circuit, a do-it-yourself battery of their transistors or a welding inverter is used as a generator.

Using a welding inverter

A do-it-yourself induction furnace for melting metal can be created using a welding inverter as a generator. This variant is the most widely used since the efforts made concern only the manufacture of the inductor:

Thin-walled copper tube is used as the main material. The recommended diameter is 8-10 cm.
The tube is bent according to the desired pattern, which depends on the features of the body used.
Between the turns there should be a distance of no more than 8 mm.
The inductor is placed in a textolite or graphite case.

After the creation of the inductor and its placement in the housing, it remains only to install the purchased crucible in its place.

Such a circuit is rather complicated in execution, it involves the use of resistors, several diodes, transistors of various capacities, a film capacitor, copper wire with two different diameters and rings from chokes. Assembly recommendations are as follows:

The created circuit is placed in a textolite or graphite case, which are dielectrics. Scheme, involving the use of transistors, is quite difficult to implement. Therefore, it is necessary to undertake the manufacture of such a furnace only if there are certain work skills.

Furnace with lamps

Recently, lamp stoves have been created less and less, as they require care when handling. The applied circuit is simpler in comparison with the case of using transistors. Assembly can be carried out in several stages:

The lamps used must be protected from mechanical impact.

Equipment cooling

When creating an induction furnace with your own hands, the most problems arise with cooling. This is due to the following points:

During operation, not only the molten metal is heated, but also some elements of the equipment. That is why effective cooling is required for long-term operation.
The method based on the use of air flow is characterized by low efficiency. In addition, it is not recommended to install fans near the oven. This is due to the fact that metallic elements can affect the generated eddy currents.

As a rule, cooling is carried out with water supply. Creating a water cooling circuit at home is not only difficult, but also uneconomical. Industrial versions of the furnace have an already built-in circuit, to which it is enough to connect cold water.

Safety

When using an induction furnace, certain safety precautions must be observed. Key recommendations:

When installing the equipment, consideration should be given to how the charge will be loaded and the molten metal will be extracted. It is recommended to allocate a separate prepared room for the installation of an induction furnace.

The following devices can be made independently:

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

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

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

Blueprints

Figure 1. Electrical diagram of an induction heater. Figure 2. Device. Figure 3. Diagram of a simple induction heater.

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

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

Additional materials and their features:

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

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

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

Nuances

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

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

Source: http://housetronic.ru/otoplenie/obogrevateli/elektroobogrevateli/indukcionnye-svoimi-rukami.html

Induction cooker diagram - basic device

The induction cooker is capable of heating metal utensils by means of induced eddy currents from a high-frequency magnetic field.

The standard scheme of an induction cooker, as a rule, is represented by an induction coil and a frequency converter, as well as an electronic control unit equipped with temperature sensors.

Introduction

Induction cookers are relatively new equipment, but already extremely popular with domestic consumers.

A feature of such stoves is the ability to heat only the bottom of the cookware.

In conventional electric stoves, the switched-on burner is initially heated.

Before choosing such equipment, it is important to familiarize yourself with the advantages of operation, as well as take into account some of the design disadvantages of the induction cooker.

The main advantages are presented:

a faster heating and cooking process, which takes several times less time than with a traditional electric stove;
the absence of burning food that can get on the hob during cooking, due to the low temperature of the burner;
reduction of consumed electrical energy due to the very rapid heating of the used kitchen utensils;
ease of use due to the ability to adjust the cooking mode on different stoves.

The advantages also include safety of operation, which is especially important for families with small children, pensioners or people with disabilities.

Induction cooker in the kitchen

Disadvantages of operation in such modern equipment are also present and, despite the fact that they are minimal, they should be taken into account when choosing a model:

turning on induction equipment at full power can create an increased load on the power grid;
for cooking on this type of stove, only special cookware with a ferromagnetic bottom should be used;
some models are characterized by the presence of a single high-frequency generator, which adversely affects the power level when all burners are turned on at the same time;
The hob is fragile, so during the entire period of operation, some care must be taken.

As practice shows, the operation of models belonging to the economy class price category is often accompanied by annoying noise and a peculiar buzz.

It is important to remember that induction cookers are capable of creating a fairly high electromagnetic type of radiation and can have a negative effect on household appliances installed at a short distance.

Scheme of the induction cooker

In accordance with the heating scheme, the electric current that comes from the mains to the coil undergoes a transformation into a magnetic field that generates vortex flows.

As a result of the interaction of the ferromagnetic bottom with the induction current, a circuit is formed, and the resulting thermal energy heats the used kitchen utensils and their contents.

The glass-ceramic surface of the stove covers an induction coil with an electric current flowing at a frequency of 50 kHz.

The standard equipment layout is relatively complex, and can vary greatly depending on the model.

The basis is represented by an oscillator, a driver on transistors of medium power and an output bipolar transistor with an insulated gate and controlling an inductor coil.

The scheme of operation of the induction cooker is reflected in the rules of service and the features of the operation of such equipment, and must also be taken into account when choosing cookware, which must be made of special materials with ferromagnetic properties.

Electrical diagram of the induction cooker

The most complex structural element is the electronic control unit, through which not only turns on, but also regulates the power level of the generator.

Modern models are characterized by the presence of an infrared sensor device that effectively controls the cooking process.

Once the cookware is removed from the hob, the hob will automatically switch off.

Do not use copper, glass, ceramic or aluminum utensils, and cleaning the surface of the induction cooker is carried out only with special products that do not have abrasive effects.

The power circuit of a standard induction cooker can vary significantly depending on the design features of the modification, but is most often represented by:

ferrite torus, which is put on the mains wire and suppresses common-mode interference;
standard fuse;
a capacitor that filters impulse noise that occurs during operation;
a resistor that operates after the mains power is turned off;
a rectifier designed for power indicators and effectively protecting the device from overvoltage;
wire shunt;
filtering system for impulse noise;
a capacitor that allows you to return energy from the oscillatory-inductor circuit to the intermediate part with constant current indicators;
a resonant capacitor that provides continuous current after the transistor is locked;
an induction device, which is focused on the transfer of heat from the surface to the bottom of the used kitchen utensils;
a transistor that converts direct current into variable indicators;
resistor to fix the transistor after shutdown;
a resistor to suppress high-frequency current indicators;
rectifier for voltage in the electrical network;
current controller, which prevents the possible occurrence of overload;
collector voltage controller.

In budget models, there are only basic structural elements, which affects the functionality of such a device.

Self-production of a simple induction cooker involves strict adherence to all standards, which will make the operation of such a device completely safe. Significant complexity in the process of designing a stove arises at the stage of selecting high-quality material to create the base of the hob.

Do-it-yourself induction cooker - diagram

Such a material must necessarily be distinguished by the ability to correctly conduct electromagnetic radiation, not conduct current and withstand high-temperature conditions.

Factory-made household cooking equipment, which includes all modern induction cookers, is made using quite expensive ceramics.

It is for this reason that the independent manufacture of an induction hob at home is associated with certain problems in choosing a worthy alternative to a ceramic surface.

Conclusion

Modern household induction hobs, as a rule, have a standard scheme, according to which the installed magnetic coils in the process of contact with the ferromagnetic bottom of the cookware carry out stable heating of the cooked food.

The control of such household equipment can be carried out by means of mechanical switches and touch buttons, which makes the operation of the induction cooker very convenient.

Source: https://microklimat.pro/otopitelnoe-oborudovanie/otopitelnye-pribory/cxema-indukcionnoj-plity.html

Do-it-yourself induction furnace - instructions!

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

DIY induction oven

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

into the electromagnetic
electrical;
thermal.

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

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

In today's article, we will talk about how an induction furnace is made by hand.

Pros and cons of induction designs

Among the many benefits are the following:

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

But there are also disadvantages.

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

Industrial Application

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

Furnaces for industrial use are divided into several types.

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

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

domestic use

Scheme of the induction furnace

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

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

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

Homemade induction oven

Scheme for the design of the generator

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

Induction furnace from high frequency generator

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

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

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

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

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

power;
frequency;
eddy losses;
heat transfer rate;
hysteresis loss.

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

Graphite brush design

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

Making an induction furnace

Assembly technology

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

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

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

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

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

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

Graphite brush design

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

Device with nichrome spiral

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

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

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

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

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

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

Finished construction

The advantages of such a design:

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

But there are, of course, downsides:

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

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

As a conclusion

Induction cooker

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

Source: https://svoimi-rykami.ru/stroitelstvo-doma/pechi_i_mangaly/indukcionnaya-pech-svoimi-rukami.html

How to make an induction boiler with your own hands

Induction heating boilers appeared on sale recently and immediately competed with the usual electric boilers with heating elements.

With similar size and power consumption, induction heaters are able to warm up the system much faster, in addition, they can work in systems with poor quality of the coolant and require less maintenance.

Applying knowledge in electrical engineering and ingenuity, you can make an induction heating boiler with your own hands.

Operating principle

The operation of induction boilers and other heating devices of this type is based on the ability of conductive materials to heat up under the action of eddy currents created as a result of electromagnetic induction.

The source of induction is a high-frequency alternating current passing through the primary winding of the heating device, made in the form of a coil. The heating element placed inside the coil plays the role of a secondary short-circuited winding. It converts electromagnetic energy into thermal energy.

Eddy currents also occur at an industrial frequency of 50 Hz, but the efficiency of the heater will be low, and the operation of the device will be accompanied by a strong hum and vibration. When the frequency is increased to 10 kHz and above, the noise disappears, the vibration becomes imperceptible, and the heating increases.

Device

An industrial induction boiler consists of a core, the role of which is played by a heat exchanger, around which a toroidal winding is wound, connected to a high-frequency converter. When current passes through the winding, an alternating electromagnetic field is created, which results in eddy currents passing through the core.

The winding is connected to a high-frequency converter, in which a signal from the control unit creates a current of the required frequency. Modern boilers have a high level of automation, which allows not only to create the optimal mode for heating the coolant, but also to turn off the device in case of an emergency.

Inside the core-heat exchanger is a coolant. Under the influence of eddy currents, it heats up to high temperatures.

Due to the difference between the temperature of the coolant at the inlet and outlet, the circulation of the coolant through the system from the boiler occurs continuously, even without connecting the pump.

Therefore, induction boilers can be used in systems with forced and natural circulation.

The coolant can be either water or antifreeze, antifreeze, oil. In this case, the quality of the liquid does not matter: the constant vibration of the system, which is imperceptible by a person, makes it impossible for scale and other impurities to settle on the walls of the heating circuit.

Outer shell- a metal case equipped with a system of thermal and electrical protection insulation.

Boiler shape it can be any, as well as the method of its installation: due to the absence of a tank inside the boiler, its dimensions are usually small, and its weight does not exceed 50 kg.

The induction boiler must not even be put into operation for a short time without filling the system with coolant! Overheating of the boiler and failure of its elements may occur!

Advantages:

High efficiency. Most manufacturers give figures of 95-98%;
Large selection of models of different power for single-phase voltage ~ 220 V or three-phase ~ 380 V;
Rapid heating of the heating system at startup;
Can work with any coolant;
The circuit through which the coolant passes inside the boiler is absolutely hermetic, which eliminates leaks and related malfunctions;
Long work without formation of a scum and deposits. It is this phenomenon that over time reduces the efficiency of boilers with heating elements and is a common cause of their breakdown due to overheating of the heating elements;
The service life declared by manufacturers is from 25 to 30 years.

Not without heaters and disadvantages, the most significant of which is the high price.

This factor usually prompts a prudent owner to assemble a home-made induction boiler from improvised materials and appliances.

Despite the complexity of the processes occurring in boilers of this type, it is possible to create a design that does not lag behind an industrial boiler in terms of basic parameters, and make an induction boiler with your own hands.

Boiler powered by a welding inverter

The design of such a homemade boiler is quite simple. The most difficult block for independent implementation, which requires knowledge of the basics of electronics and electrical engineering, is a high-frequency converter. Its function is perfectly performed by a modern-type welding inverter capable of delivering an output signal with a frequency of 20-50 kHz.

In addition, for installation you will need:

copper wire in enamel insulation with a diameter of 1-1.5 mm;
insulated wire with terminals for connecting the winding to the inverter;
trimmings of stainless steel wire with a diameter of 3-5 mm, 5 cm long;
fine stainless steel mesh;
a section of a water pipe made of sewn polyethylene or polypropylene for hot water and heating systems with a diameter of 50 mm and a wall thickness of 8.4 mm, length - 1 m;
adapters from a 50 mm pipe to pipes used in an existing or planned heating system, a tee for connecting an emergency valve and two ball valves;
strips of textolite for fastening the winding;
epoxy adhesive for winding insulation;
the body of a homemade boiler, it can be made from a metal or plastic distribution cabinet, in which you can install an inverter and fix the heating element.

The sequence of assembly and installation of elements:

On a segment of a polypropylene pipe with a diameter of 50 mm, using epoxy glue, 4 strips of textolite 8-10 mm wide are attached, stepping back from the ends of the pipe by 70-100 mm. A winding will be wound on them. To fix the extreme turns of the winding in the textolite, grooves can be made.
50-100 turns of copper wire are wound in enamel insulation. The turns should be approximately 0.3-0.6 mm apart at an equal distance. The exact number of turns depends on the diameter of the wire used and its resistivity, as well as the output parameters of the inverter.
When installing a homemade boiler in a residential area, it is recommended to perform a toroidal winding to reduce the external electromagnetic field. The toroidal winding consists of the same number of oppositely directed turns, while the electromagnetic fluxes are mutually compensated and pass only along the inner loop.
A stainless steel mesh is inserted into the pipe from one end of it and tightly packed on the other side with pieces of stainless wire - it will heat up under the influence of eddy currents. It is recommended to use stainless steel so that corrosion damage of the wire does not occur over time, but theoretically any conductive metal, including wire rod, will do. The other end of the pipe is also closed with a mesh.
Polypropylene adapters are soldered to both ends of the pipes to the diameter used in the heating system. Ball valves are installed on them to shut off the circulation and remove the heat exchanger for revision.
An emergency valve is installed on the side of the upper outlet adapter to relieve pressure.
The winding is coated with epoxy glue to ensure high-quality electrical insulation of the winding. The manufacture of glue is recommended to be carried out with a slight deviation from the instructions, adding 10-15% less hardener. This will make the insulation less brittle.
They are attached to the terminals of the winding wires in insulation using crimp terminals. The other end of the wire must be equipped with terminals for connection to the inverter. The diameter of the wires must be able to withstand the maximum output current of the inverter.
Install the heat exchanger in the cabinet, fixing it on brackets made of heat-resistant non-conductive material. Textolite can be used.
Connect the heater to the system and fill it with water.
An inverter is placed at the bottom of the cabinet. Connect the terminals to it and turn it on to the network. The boiler is started and the mode is set.

The cabinet body made of metal must be grounded!

From induction hob

An induction boiler can also be made on the basis of an induction hob. To do this, the heating element of the tile is disassembled and a copper wire is used for winding on a core made in the above way.

The tile control unit is used to power the resulting winding, setting the required power on the touch control panel.

However, this method has significant disadvantages:

For the successful operation of such a home-made boiler, it is necessary to calculate the parameters of the inductance of the newly assembled coil. They may not match those for which the tile electronics are designed, as a result of which the control unit may fail. For calculations, you need to have good knowledge in the field of electrical engineering and be able to understand the connection diagram;
Most stove models are equipped with an automatic shutdown after 2-3 hours after the start of the burner. This will lead to a regular shutdown of the boiler;
Induction type stoves usually have a power of no more than 2.5 kW, therefore they are only suitable for conversion to a low power boiler.

Errors in the device of an induction tile boiler are shown in the video:

An easier way to use an induction hob, excluding disassembly of the device and installation of a new circuit - install a sealed stainless steel tank of a suitable size on it with an inlet and outlet fitting and connecting it as a boiler to the heating system. Almost everyone can cope with such a connection scheme.

If you have the necessary knowledge and ability to understand the circuits, you can follow the example of the author of the video and assemble a functional induction boiler from tiles, finalizing its circuit.

Dry type heater

The principle of operation of an induction boiler involves the use of water or other liquid not only as a heat carrier, but also to cool the core.

But the heating of the secondary winding, the role of which in this device is played by a pipe with water, will also occur if it consists only of metal.
The degree of heating in this case depends on the ratio of the strength of the electromagnetic field created by the winding and the mass of the core metal.

After making the calculations, you can create a dry induction heater with your own hands from metal pipes and copper winding, as shown in the video.

The use of an induction boiler is cheaper than a conventional electric boiler with heating elements, and a home-made design will significantly reduce the cost of its installation. Similarly, you can assemble a flow-type water heater for installation in the country, choosing a device of the required power.