DIY induction boiler. How to make an induction heater with your own hands

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

The closed conductor in induction cookers is metal utensils, which is heated by eddy electric currents. In general, the operating principle of such devices is not complicated, and if you have a little knowledge of physics and electrical engineering, assembling an induction heater with your own hands will not be difficult.

The following devices can be made independently:

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

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

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

1. Ideally conduct electromagnetic radiation.
2. Not a conductive material.
3. Withstand high temperature load.

In household cookers induction surfaces Expensive ceramics are used when made at home induction cooker, finding a worthy alternative to such material is quite difficult. Therefore, first you should design something simpler, for example, an induction furnace for hardening metals.

Manufacturing instructions

Drawings

Figure 1. Electrical diagram induction heating calf
Figure 2. Device. Figure 3. Schematic of a simple induction heater

To make a furnace you will need following materials and tools:

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

Additional materials and their features:

1. For making a coil, which will emit the alternating magnetic field necessary for heating, it is necessary to prepare a piece of copper tube with a diameter of 8 mm and a length of 800 mm.
2. Powerful power transistors are the most expensive part of a homemade induction installation. To install the frequency generator circuit, you need to prepare 2 such elements. Transistors of the following brands are suitable for these purposes: IRFP-150; IRFP-260; IRFP-460. When manufacturing the circuit, 2 identical of the listed field-effect transistors are used.
3. For the manufacture of an oscillatory circuit you will need ceramic capacitors with a capacity of 0.1 mF and an operating voltage of 1600 V. In order for high-power alternating current to form in the coil, 7 such capacitors will be required.
4. When operating such an induction device, field-effect transistors will get very hot and if radiators from aluminum alloy, then after just 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 effectiveness of such cooling will be minimal.
5. Diodes, which are used in an induction heater, must be ultra-fast acting. The most suitable diodes for this circuit are: MUR-460; UF-4007; HER – 307.
6. Resistors used in circuit 3: 10 kOhm power 0.25 W – 2 pcs. and 440 Ohm power - 2 W. Zener diodes: 2 pcs. with an operating voltage of 15 V. The power of the zener diodes must be at least 2 W. A choke for connecting to the power terminals of the coil is used with induction.
7. To power the entire device you will need a power supply with a power of up to 500 W. and voltage 12 - 40 V. You can power this device from a car battery, but you won’t be able to get the highest power readings at this voltage.

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

1. From copper pipe a spiral with a diameter of 4 cm is made. To make a spiral, you should copper tube screw onto a rod with a flat surface with a diameter of 4 cm. The spiral should have 7 turns, which should not touch. Fastening rings are soldered to the 2 ends of the tube for connection to the transistor radiators.
2. The printed circuit board is made according to the diagram. If it is possible to install 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 operate much more stable. The capacitors in the circuit are installed in parallel to form an oscillating circuit with a copper coil.
3. Heating the metal occurs inside the coil after the circuit is connected to the power supply or battery. When heating the metal, it is necessary to ensure that there is no short circuit in the spring windings. If you touch 2 turns of the coil at the same time with heated metal, the transistors will fail instantly.

Nuances

1. When conducting experiments on heating and hardening of metals, inside the induction coil the temperature can be significant and amounts to 100 degrees Celsius. This thermal heating effect can be used to heat water for domestic use or for heating a home.
2. Diagram of the heater discussed above (Figure 3), at maximum load is capable of providing radiation of magnetic energy inside the coil equal to 500 W. This power is not enough to heat a large volume of water, and the construction of a high-power induction coil will require the manufacture of a circuit in which it will be necessary to use very expensive radio elements.
3. Budget solution for organizing induction heating of liquids, is the use of several devices described above, located in series. In this case, the spirals must be on the same line and not have a common metal conductor.
4. Asa pipe from stainless steel with a diameter of 20 mm. 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. At simultaneous switching on 4 such devices, the heating power will be about 2 kW, which is already sufficient for flow-through heating of liquid with a small circulation of water, to values ​​​​allowing the use this design in supply warm water small house.
5. If you connect this heating element with well insulated tank, which will be located above the heater, the result will be a boiler system in which the liquid will be heated inside stainless pipe, the heated water will rise up, and its place will be taken by a colder liquid.
6. If the area of ​​the house is significant, then the number of induction coils can be increased to 10 pieces.
7. The power of such a boiler can be easily adjusted by turning off or turning on the spirals. The more sections that are turned on at the same time, the greater the power of the heating device operating in this way.
8. To power such a module you will need a powerful power supply. If inverter is available welding machine DC, then a voltage converter of the required power can be made from it.
9. Due to the fact that the system operates at constant electric current , which does not exceed 40 V, the operation of such a device is relatively safe, the main thing is to provide a fuse block in the generator power circuit, which in the event of a short circuit will de-energize the system, thereby eliminating the possibility of a fire.
10. You can organize “free” home heating in this way., subject to installation for powering induction devices batteries, which will be charged using solar and wind energy.
11. The batteries should be combined into 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 boiler operates at high power. Besides this, serial connection will reduce the current in the circuit and increase the service life of the batteries.

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

Recently the need arose to create a small induction heater with your own hands. Wandering around the Internet, I found several diagrams of induction heaters. Many schemes were not satisfactory due to the rather complex wiring, some did not work, but there were also working options.

A few days ago I came to the conclusion that an induction heater can be made from an electronic transformer at minimal cost.

The principle of induction heating is the effect of Foucault currents on metal. Such a heater is actively used in the most different areas science and technology. In theory, Foucault currents are indifferent to the types and properties of metals, so the inductor can heat or melt absolutely any metal.

An electronic transformer is a pulsed power supply on the basis of which our heater is built. This is a simple half-bridge inverter built on two powerful bipolar transistors of the MJE13007 series, which overheat terribly during operation, so they need a very good heat sink.

First, you need to remove the main transformer from the electronic transformer. We will make a kind of inductor based on a ferrite cup. To do this, take a 2000NM cup (the size of the cup is not particularly important, but preferably larger). We wind 100 turns of 0.5 mm wire on the frame, remove the varnish coating from the ends of the wires and tin them. Then we solder the ends of the wires in place of the standard pulse transformer - everything is ready!

The result is a fairly powerful homemade induction heater (efficiency no more than 65%), on the basis of which you can even assemble a small induction stove. If you take a piece of metal and bring this metal closer to the center of the coil, then after a few seconds the metal will heat up. With such a heater you can melt wires with a diameter of 1.5 mm - I succeeded in just 20 seconds, but at the same time the high-voltage ET transistors got so hot that you could fry eggs on them!

During operation, there may be a need for additional cooling for the heat sinks, since experience has shown that the heat sink simply does not have time to remove heat from the transistors.

The basic operation of such an inverter is quite simple. The induction heater circuit itself is convenient in that it does not require any configuration(in more complex circuits there is often a need to adjust the circuit to the resonance frequency, accurately calculate the number of turns and diameter of the circuit wire, as well as count the circuit capacitor, but here all this is not present and the circuit works immediately).

The mains voltage (220 Volts) is first rectified by a diode rectifier, then supplied to the circuit. The frequency is set by a DB3 dinistor (diac). The circuit itself does not have any protection, only a limiting resistor at the power input, which supposedly should work as a mains fuse, but at the slightest problem the transistors are the first to fly out. The reliability of the induction heater circuit can be increased by replacing the diodes in the rectifier with more powerful ones, adding a mains filter to the input of the circuit, and replacing the power transistors with more powerful ones, say, MJE13009.

In general, I do not recommend turning on such a heater for for a long time, if there is no active cooling, otherwise you will be forced to change transistors every 5 minutes.

The goal is practical implementation heating a house using metal induction melting techniques. The idea is not new and is to place the inductor around the heating pipe. By heating the pipe, we thereby heat the water that circulates in the heating system. The basic prerequisite that can significantly reduce energy costs is an oscillatory circuit (inductor->capacitors) that operates in resonance. The voltage increases by about tens of times, which heats the metal.

Classic induction circuits, as practice has shown, replacing failing transistors requires expensive components. The basis was taken as an induction heating circuit using the ZVS (zero voltage switching) method of switching transistors. The diagram is taken from the site http://www.rmcybernetics.com/projects/DIY_Devices/diy-induction-heater.htm.

IN assembled circuit, transistors STP40N10, Schottky diodes 50SQ100 5A, 100V were used; resistors are 240 ohms, the measured capacity of the capacitor bank CBB81/224/2000V is 2.3 uF. The magnetic permeability of the ferrite ring is L2, according to the seller 10000, but the circuit starts with a ferrite ring. Power supply - two batteries replaced with an OSM1-1.6 transformer with an alternating voltage of 24 volts and a constant voltage of about 27 volts on the capacitor. The scheme worked immediately, no settings were required. A more or less interesting result for a given inductor size starts at 20 volts.

The voltage on each of the transistors relative to the housing is 800 Volts, no matter where you measure it. Frequency of operation of the circuit without metal pipe in the inductor, 321 KHz, current consumption 1.7 Amperes. When adding a metal pipe, the frequency drops to 138 KHz, the current consumption increases to 5A. A 0.5-inch pipe, with an inductor with an internal diameter of 85 mm, is heated in the area of ​​the midpoint to a cherry color.

It is best to use film capacitors from Evox Rifa, Faratronic, and Pilcor in such circuits. The efficiency will increase, and the number of air conditioners will be required several times less.

The current consumption is determined by filling the inductor with metal. Worth using seamless pipe with maximum wall thickness. With a current consumption of more than 12 amperes, STP40N10 transistors do not last long. The water cooling recommended on the site is not used. The radiator and inductor are heating up, the capacitors are cold. To cool the transistor radiators, I used a computer fan. If necessary, heat removal can be organized on the same heating riser.

Current transformer.

Second, no less, if not more in an interesting way heating the coolant is a current transformer. The current transformer is a ferrite ring mounted on a wire running from the capacitor block to the inductor. Ferrite rings of any magnetic permeability are suitable. Including a ring made of transformer iron. The lower the magnetic permeability of the magnetic core, the smaller the radius of the ring is permissible, the lower the frequency of the output current, the more the magnetic core heats up. In the case of using transformer iron, heating efficiency is maximum. Ferrite rings with inner diameter less than 60mm for long work do not use diagrams. When the internal diameter of the ferrite ring is small, less than 50 mm, the current consumption required to maintain resonance sharply increases, and the transistors fail. In the case of using a core from a fuel assembly, a gap is required, this is not according to Feng Shui. In the case of counter-winding windings, as shown in the photograph, there is no emf.

Below is a load connection diagram. You can turn on a 220V 95W lamp without a diode bridge, but you should reduce the number of turns of the current transformer to about five, otherwise the lamp will burn out. You should not pay attention to the double pair of turns used in winding. The same should be done with a pair of wires, black and red, which were connected to them on transistor radiators high voltage capacitors from microwave ovens. The capacitors got very hot, I had to replace them, let them keep the wires for now.

Ferrite rings placed in the inductor increase the frequency to 400 kHz, the current transformer lowers it to 100 kHz. The brightness of the lamp is adjusted by frequency by increasing or decreasing the core of ferrite rings in the inductor.

The tester shows that when the load was connected, the current increased by two amperes. (In the first case, the current must be multiplied by 100) This is approximately equal to the power of the lamp used. There is no free energy withdrawal from a current transformer. Connecting an active load increases the current consumed by the device. But using ferrite rings to heat the coolant in addition to the inductor is a very interesting option.

Arc discharge.

For every three or four turns of a current transformer there are 1000 volts. An attempt to measure the voltage at more turns ended in failure due to failure of the tester. It can be assumed that the voltage at the current transformer is about five to six thousand volts, so the third heat source in the proposed circuit is an arc discharge. I have not yet decided how to use it to heat the coolant. Anything with which the arc discharge is in close contact melts.

Subtotal.

1. Heat the heating pipe using Foucault currents.
2. Additional thermal power due to cooling of radiators on which transistors are installed.
3. Cooling the ferrite of the current transformer with coolant (water).
4. Using an arc discharge is problematic. Very high temperature. But very promising. The presence of an arc does not increase the current consumption of the device.

Example man pages:

Download the full manual:

A simple induction heater consists of powerful generator high frequency and low-resistance coil-circuit, which is the load of the generator.

A self-excited generator generates pulses based on the resonant frequency of the circuit. As a result, a powerful alternating electromagnetic field with a frequency of about 35 kHz appears in the coil.
If a core of conductive material is placed in the center of this coil, electromagnetic induction will occur inside it. As a result of frequent changes, this induction will cause eddy currents in the core, which in turn will lead to the release of heat. This is the classic principle of converting electromagnetic energy into thermal energy.
Induction heaters have been used in many areas of production for a very long time. With their help, you can do hardening, non-contact welding, and most importantly, spot heating, as well as melting of materials.
I'll show you the circuit of a simple low-voltage induction heater, which has already become a classic.

We will simplify this circuit even further and will not install zener diodes “D1, D2”.
Items you will need:
1. 10 kOhm resistors – 2 pcs.
2. 470 Ohm resistors – 2 pcs.
3. Schottky diodes 1 A – 2 pcs. (Others are possible, the main thing is for a current of 1 A and high-speed)
4. Field-effect transistors IRF3205 – 2 pcs. (you can take any other powerful ones)
5. Inductor “5+5” - 10 turns with a tap from the middle. The thicker the wire, the better. Wrapped on a wooden round stick, 3-4 centimeters in diameter.
6. Throttle - 25 turns on a ring from an old computer block.
7. Capacitor 0.47 µF. It is better to collect the capacitance with several capacitors and for a voltage of at least 600 Volts. At first I took it to 400, as a result of which it began to heat up, then I replaced it with a composite of two in series, but they don’t do that, I just didn’t have any more at hand.

Making a simple 12V induction heater

I collected the whole circuit wall-mounted, separating the inductor from the entire circuit with a block. It is advisable to place the capacitor in close proximity to the coil terminals. Not like mine in this example in general. I installed transistors on radiators. The entire installation was powered by a 12 Volt battery.

Works great. The blade of a stationery knife heats up to red very quickly. I recommend everyone to repeat it.
After replacing the capacitor they no longer got hot. The transistors and the inductor itself get hot if they work constantly. For a short time - almost not critical.

Induction heater- a device for heating metals by exposure to Foucault currents. The very principle of such a heater has been known for a long time, and now induction heaters are actively used in many areas of industry. Our homemade inductor is easy to use, has relatively simple design and does not require any configuration. At the same time, the heater is quite powerful.

The inductor circuit operates on the principle of series resonance. You can increase the power of the device in several ways - by selecting more powerful field switches, using a larger capacitor in the circuit, or increasing the supply voltage.

I assembled such an inductor with my own hands, purely out of curiosity, to check the functionality of the circuit.

Choke - took a ready-made one from a computer power supply. It is wound on a ring of powdered iron and contains 10-25 turns of 1.5mm wire.

Field-effect transistors - there is a large choice here, in my case I used N-channel high-voltage field-effect transistors of the IRF740 series, but it is advisable to use field-effect transistors based on the minimum resistance of the open junction, as well as the maximum permissible current. IN standard version It is recommended to use power switches of the IRFP250 series.

Parameters of this transistor:

• N-channel structure
• Maximum drain-source voltage Usi: 200 V
• Maximum drain-source current at 25 ºС Isi max.: 30 A
• Maximum gate-source voltage Uzi max: ±20 V
• Channel open resistance Rsi on: 85 mOhm
• Maximum power dissipation Psi max: 190 W
• Slope characteristic S: 12000 mA/V
• Housing: TO247AC
• Gate threshold voltage: 4 V

A very powerful and quite expensive transistor, but with it you can get high power, and the consumption can be in the region of 20-40 Amperes!!!

The contour was wound on a frame with a diameter of 4.5 cm and consists of 2x3 turns. I advise you to wind 6 turns at once, then remove the varnish from the 3rd turn small area and solder the wire there, which will be a tap; a power plus is supplied to it. In my case, a 1.5mm wire was used to wind the circuit, but ideally you need a 3-5mm wire, it is wound according to the same principle.

Zener diodes are 12-15 Volts, preferably with a power of 1-2 watts, all resistors used are 0.5 watts.

Diodes - you definitely need fast ones with a reverse voltage of at least 400 Volts, you can install cheap ultrafast UF4007, in my case diodes of the HER305 series were used - with a reverse voltage of 400 Volts, with permissible current 3 Amp.

Increasing the power of the circuit means increasing the current in the circuit. How more capacity capacitor C1, the greater the current. In my case, 250 Volt films were used, 6 pieces 0.33 μF, but the number of capacitors in the standard version is recommended to be 15-20 pieces with the same capacity, the capacitor voltage is 250-400 Volt.

The main disadvantage of the scheme- an incredible amount of heat generation on the transistors, with my rather good switches I had to cool the circuit with two coolers, but even they did not have time to properly remove the heat, so I will think about water cooling...

A homemade inductor can quickly heat up M6 standard bolts to a yellow tint.