How to assemble an induction furnace - diagrams and instructions. Construction of induction cookers How to make a Chinese induction oven

So I give everyone the example of both China and the West..
While I had a welder weighing more than 40 kg, the meter did not hold well and the plugs flew out, I could not transport it without a car, and I tore my belly button to carry it, I dreamed of small machines and welding aluminum with an ordinary welder. And all the smart electronics engineers did not shake their brains, and referred to clever formulas.
But then the West poured in, followed by China... And Miracles began!!! And now LED lamp gives approximately the same luminous flux, but takes 10 times less electrical energy, Welding machines are almost 20 times lighter!!! I now have such an inverter that weighs 2.5 kg, works with electrodes from 1 mm2 to 4 mm2 in cross section, and consumes three times less electricity. And I don’t care about J. Lenz’s laws, or whatever they are... I got more economical, practical, profitable products and tools. And that means it works, despite our clever people from the 17th century!!! I personally need practical things that save my budget. And, by the way, regarding the heating and power of these air heaters... they came up with MONOPOLY formulas from the Government that did not exist under the USSR Supply and Sales and State Construction Committee system. Then the power of paid thermal energy was calculated and paid according to the delivered power of each section of the heating battery, which was also measured in Gcal. I worked in the supply system and dealt with a range of more than 10,000 products. And that’s why I’m simply going crazy because they now consider it not to flow per unit of time. hot water, and the difference in temperature loss at the input to the output, but are calculated by kW per 1 m2 instead of 1 kW of one section of a cast iron or aluminum battery, and refer to the convection heat of walls, ceilings, and others load-bearing structures. It seems that these carriers also emit heat, which also needs to be taken into account when consuming coolant. But not by the sensor on the section, and not by the volume of coolant passed per unit of time. Namely, these units must consider the cost of money for the production and release of this heat. But who will check this at the Government Level?? He needs to collect more money from the population through the monopolies of Lukoil and other resource providers. That is why these few calculation norms have been introduced to charge payments from the population, which includes smart debaters. And therefore, the smart people who think that for 1 m2, then for induction of walls... I ask you to better keep quiet.
This estimate covers the Owner's heating costs when choosing a heater. It needs to be illuminated, and not to show knowledge of THEORY of the 17th-19th centuries...
Look outside and at the Calendar. Now it is already the 2nd decade of the 21st Century. And the satellites are returning from Venus.. And you are sitting there on the heating elements... Well, just sit. I choose induction heating and water heater. My pension tells me so.

The idea of ​​heating metal with Foucault eddy currents excited by electrical magnetic field coils are by no means new. It has long been successfully used in industrial melting furnaces, forges, household heating devices - stoves and electric boilers. The latter are quite expensive, so home craftsmen do not give up trying to make an induction water heater with their own hands. Our task is to consider workable options for home-made devices and figure out whether they can be used for heating a house.

About the principle of inductive heating

First, let's explain how electric induction heaters function. Alternating current, passing through the turns of the coil, forms an electromagnetic field around it. If you place a magnetic metal core inside the winding, it will become heated by eddy currents arising under the influence of the field. That's the whole principle.

Important condition. In order for the metal core to heat up, the coil must be powered alternating current, changing the sign and vector of the field with high frequency. When you apply DC current to the winding, you get an ordinary electromagnet.

The heating element itself is called an inductor and is the main part of the installation. IN heating boilers he is steel pipe with coolant flowing inside, and in kitchen stoves - a flat coil, as close as possible to the hob, as shown in the photo below.

The second part of the induction heater is a circuit that increases the frequency of the current. The fact is that voltage with an industrial frequency of 50 Hz is of little use for the operation of such devices. If you connect the inductor directly to the network, it will begin to hum strongly and weakly warm up the core, together with the windings. In order to effectively convert electricity into heat and completely transfer it to the metal, the frequency must be increased to at least 10 kHz, which is what the electrical circuit does.

What are the real advantages of induction boilers over heating and electrode boilers:

1. The part that heats the water is a simple piece of pipe that does not participate in electrochemical processes (as in electrode heat generators). Therefore, the service life of the inductor is limited only by the performance of the coil and can reach 10-20 years.
2. For the same reason, the element is equally good friends with all types of coolants - water, antifreeze and even machine oil, there is no difference.
3. The insides of the inductor are not covered with scale during operation.

Homemade device options

The Internet contains a sufficient number of different designs created for various purposes. Take a small-sized induction heater made from a 250-500 W computer power supply. The model shown in the photo will be useful to a master in a garage or car service for melting rods made of aluminum, copper and brass.

But the design is not suitable for heating premises due to its low power. There are two on the Internet real options, whose tests and work were filmed:

• water heater from polypropylene pipe powered by welding inverter or an induction cooktop;
• steel boiler heated by the same hob.

Reference. There are others, completely homemade designs, where craftsmen assemble frequency converters from scratch. But this requires knowledge and skills in the field of radio engineering, so we will not consider them, but will simply give an example of such a circuit.

Now let's take a closer look at how to make induction heaters with your own hands, and most importantly, how they then function.

We make a heating element from a pipe

If you have been actively searching for information on this topic, you have probably come across this design, since the master posted its assembly on the popular YouTube video resource. After which many sites posted text versions of the manufacture of this inductor in the form step by step instructions. Briefly, the heater is made like this:

An important nuance. The length and cross-section of the wire for winding the coil should be determined from the standard inductor of the stove so that it matches the power of the field-effect transistors in the electrical circuit. If you take more wire, the heating power will drop; if you use less, the transistors will overheat and fail. How it looks visually, look at the video:

As you might guess, the role heating element Here metal pipe cleaners are played, located in the alternating magnetic field of the coil. If you run the hob at maximum, while simultaneously passing running water through an improvised boiler, it can be heated by 15-20 °C, as tests of the unit have shown.

Since the power of the majority induction cookers lies within 2-2.5 kW, then using a heat generator you can heat the premises with total area no more than 25 m². There is a way to increase the heating by connecting an inductor to a welding machine, but this has its own difficulties:

1. The inverter outputs D.C., but you need a variable. To connect an induction heater, you will have to disassemble the device and find the points on the diagram where the voltage has not yet been rectified.
2. You need to take a wire of a larger cross-section and select the number of turns by calculation. As an option, copper wire Ø1.5 mm in enamel insulation.
3. It will be necessary to organize cooling of the element.

The author demonstrates checking the performance of an inductive water heater in his video presented below. Tests have shown that the unit requires improvement, but the final result, unfortunately, is unknown. It looks like the craftsman left the project unfinished.

How to assemble an induction boiler

In this case, there is no need to disassemble the cheap Chinese stove. The point is to weld a boiler tank according to its dimensions, following step-by-step instructions:

1. Take steel profile pipe 20 x 40 mm with a wall thickness of 2 mm and cut blanks from it to the width of the panel.
2. Weld the tubes together lengthwise, joining the smaller sides.
3. Weld hermetically to the ends at the top and bottom iron caps. Make holes in them and install threaded pipes.
4. Attach 2 corners to one side by welding so that they form a shelf for the induction stove.
5. Paint the unit with heat-resistant spray enamel. The assembly process is shown in more detail in the video.

Final assembly and commissioning consists of mounting the boiler on the wall and inserting it into the heating system. Hob is inserted into the socket from the corners on the rear wall of the tank and connected to the power supply. All that remains is to turn on the heating of the inductor.

Here you are faced with the same problem that occurred with the previous model. Undoubtedly, induction heating will work, but its power of 2.5 kW is enough to heat a couple small rooms when it's cold outside. In autumn and spring, when the temperature has not dropped below zero, a homemade boiler can heat an area of ​​35-40 m². How to properly connect it to the system, see the next video:

We intentionally presented options. induction water heaters simple design so that anyone can make a similar unit on their own. But the question remains: is it necessary to engage in this business and spend own time. There are a number of objective considerations in this regard:

1. Users who do not understand electrical and radio engineering are unlikely to be able to increase the heating power above 2.5 kW. To do this, you will have to assemble a frequency converter circuit.
2. The efficiency of the inductor is no higher than that of other electric boilers. But assembling a heater with heating elements is much easier.
3. If you don't have it lying around at home induction hob, then you will need to buy it for about 80 USD. e. This is how much cheap Chinese products cost in online stores. Ready-made electrode boilers with a power of up to 10 kW are sold for the same money.
4. Electric stoves are equipped with automatic safety switches household appliance after 1 or 2 hours of work. This causes inconvenience during operation.
5. If, for various reasons, the coolant leaks out of a homemade heat generator, then the heating will not stop. This is fraught with fire.

Of course, you can do without expensive purchases, thoroughly understand the design and make an induction heater from scratch. But you won’t be able to do everything for free, because you will need to purchase components for the circuit. Please note that the bonuses from such a heating unit are small, so it is not advisable to seriously undertake its manufacture for the purpose of heating a private home.

Induction furnaces were invented back in 1887. And within three years, the first industrial development appeared, with the help of which various metals were smelted. I would like to note that in those distant years these stoves were a novelty. The thing is that scientists of that time did not quite understand what processes were occurring in it. Today we figured it out. In this article we will be interested in the topic - do-it-yourself induction furnace. How simple is its design, is it possible to assemble this unit at home?

Principle of operation

You need to start assembling by understanding the principle of operation and structure of the device. Let's start with this. Pay attention to the figure above, we will understand it according to it.

The device includes:

• Generator G, which produces alternating current.
• Capacitor C, together with coil L, creates an oscillating circuit, which provides the installation with high temperature.
  

  Attention! Some designs use a so-called self-oscillating generator. This makes it possible to remove the capacitor from the circuit.

• The coil in the surrounding space forms a magnetic field in which there is a voltage, indicated in our figure by the letter “H”. The magnetic field itself exists in free space, and can be closed through a ferromagnetic core.
• It also acts on the charge (W), in which it creates a magnetic flux (F). By the way, instead of the charge, some kind of blank can be installed.
• The magnetic flux induces a secondary voltage of 12 V. But this only happens if W is an electrically conductive element.
• If the heated workpiece is large and solid, then the so-called Foucault current begins to operate inside it. It is of the vortex type.
• In this case, eddy currents are transmitted from the generator through a magnetic field thermal energy, thereby heating the workpiece.

The electromagnetic field is quite wide. And even the multi-stage energy conversion, which is present in homemade induction furnaces, has maximum efficiency - up to 100%.

Crucible furnace

Varieties

There are two main designs of induction furnaces:

• Duct.
• Crucible.

We won’t describe them all here. distinctive features. Just note that the duct option is a design that is similar to welding machine. In addition, in order to melt metal in such furnaces, it was necessary to leave a little melt, without which the process simply would not work. The second option is an improved scheme that uses technology without residual melt. That is, the crucible is simply installed directly into the inductor.

How it works

Why do you need such a stove at home?

In general, the question is quite interesting. Let's look at this situation. There is a fairly large number of Soviet electrical and electronic devices that used gold or silver contacts. These metals can be removed different ways. One of them is an induction stove.

That is, you take the contacts, put them in a narrow and long crucible, which you install in the inductor. After 15-20 minutes, reducing the power, cooling the apparatus and breaking the crucible, you will get a rod, at the end of which you will find a gold or silver tip. Cut it off and take it to a pawnshop.

Although it should be noted that with the help of this homemade unit you can carry out various processes with metals. For example, you can harden or temper.

Coil with battery (generator)

Stove components

In the section "Operating principle" we have already mentioned all the parts induction furnace. And if everything is clear with the generator, then the inductor (coil) needs to be sorted out. A copper tube is suitable for it. If you are assembling a device with a power of 3 kW, then you will need a tube with a diameter of 10 mm. The coil itself is twisted with a diameter of 80-150 mm, with a number of turns from 8 to 10.

Please note that the turns copper tube should not touch each other. Optimal distance there are 5-7 mm between them. The coil itself should not touch the screen. The distance between them is 50 mm.

Typically, industrial induction furnaces have a cooling unit. It is impossible to do this at home. But for a 3 kW unit, working for up to half an hour does not threaten anything. True, over time, copper scale will form on the tube, which reduces the efficiency of the device. So the coil will have to be changed periodically.

Generator

In principle, making a generator with your own hands is not a problem. But this is only possible if you have sufficient knowledge in radio electronics at the level of an average radio amateur. If you don’t have such knowledge, then forget about the induction stove. The most important thing is that you also need to skillfully operate this device.

If you are faced with the dilemma of choosing a generator circuit, then take one piece of advice - it should not have a hard current spectrum. To make it clearer what we're talking about we're talking about, we offer the most simple diagram generator for an induction furnace in the photo below.

Generator circuit

Required knowledge

The electromagnetic field affects all living things. An example is microwaved meat. Therefore, it is worth taking care of safety. And it doesn’t matter whether you are assembling the stove and testing it or working on it. There is such an indicator as energy flux density. So it depends on the electromagnetic field. And the higher the frequency of radiation, the worse it is for the human body.

Many countries have adopted safety measures that take into account energy flux density. There are developed acceptable limits. This is 1-30 mW per 1 m² of the human body. These indicators are valid if exposure occurs no more than one hour per day. By the way, the installed galvanized screen reduces the density of the ceiling by 50 times.

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

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

A homemade device is unlikely to be suitable for performing complex tasks, but it will cope with basic functions. The device can be assembled on the basis of a working welding inverter made of transistors, or using lamps. The most productive device is the one based on lamps due to its high efficiency.

Working principle of induction furnace

Heating of the metal placed inside the device occurs by converting electromagnetic pulses into heat energy. Electromagnetic pulses are generated by a coil with turns made of copper wire or pipes.

Diagram of an induction furnace and heating circuits

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

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

Varieties

Induction coil stoves are usually divided into two types depending on the type of construction:

• Duct;
• Crucible.

In the first devices, the metal to be melted is located in front of the induction coil, and in the second type of furnace it is placed inside it.

You can assemble the oven by following these steps:

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

Use for heating

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

Another disadvantage is based on the device's consumption large volumes electricity during operation, therefore the device falls into the category of economically unprofitable.

System cooling

A device assembled independently must be equipped with a cooling system, since during operation all components will be exposed to high temperatures, the structure may overheat and break. In store-bought ovens, cooling is done with water or antifreeze.

When choosing a cooler for your home, preference is given to options that are most profitable for sale with economic point vision.

For home ovens, you can try using a regular paddle fan. Please note that the device should not be placed too close to the furnace, as metal parts of the fan negatively affect the performance of the device and can also open vortex flows and reduce the performance of the entire system.

Precautions when using the device

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

• Some elements of the installation, as well as the metal that is melting, are subject to intense heat, resulting in a risk of burns;
• When using a lamp oven, be sure to place it in a closed case, otherwise there is a high risk of electric shock;
• Before working with the device, remove all metal elements and complex electronic devices from the operating area of ​​the device. The device should not be used by people who have a pacemaker.

An induction type metal melting furnace can be used for tinning and forming metal parts.

A homemade installation can be easily adjusted to suit specific conditions by changing some settings. If you adhere to the indicated diagrams when assembling the structure, and also follow basic safety rules, homemade device will practically not be inferior to store-bought household appliances.

The article discusses industrial induction circuits melting furnaces(channel and crucible) and induction hardening units 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 power during the period of finishing the metal to the desired level chemical composition(with 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. For continuous furnaces and mixers, the induction units are not switched off when draining metal and loading new portions of the charge.

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 a high-voltage industrial frequency network.

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 block diagram 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. Figure 4 shows a schematic diagram of the power supply of an 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.