DIY induction heater made from welding. Induction heater: diagram and procedure for making it yourself Inductive heater

A furnace for melting metals at home can also be used to quickly heat metal elements, for example, when tinning or forming them. The operating characteristics of the presented installations can be adjusted to a specific task by changing the parameters of the inductor and the output signal of the generating sets - this way you can achieve their maximum efficiency.

An induction heater is a resonant inverter operating at a frequency below resonance. It consists of a power supply, driver board, control board, matching transformer and other parts that are located on the chassis of the device. The inverter is built according to the “resonance in the primary” topology, this reduces the dimensions and is more technologically advanced in manufacturing.

Main nodes. A power supply that has four galvanically isolated power windings. Two for powering the drivers, one for powering the control board and a power one for powering the coolant pump, fan and start relay. The first three are stabilized at 12 V, the last one has no stabilization. The drivers control IGBT transistors connected two in parallel.

The matching transformer consists of three E80/38/20 E80/38/20 E-shaped ferrite cores folded together. A winding of 10 turns of 4mm2 stranded wire is wound around it and filled with epoxy glue.

A special feature of my inverter is that its operating frequency is lower than the resonant frequency. When operating below resonance, the switches open very harshly and turn off at zero current. Hard switching is caused by through currents, which cannot be eliminated, but can be significantly reduced. To do this, the damping inductor Dr1, with a snubber, is included in the inverter power circuit (plus or minus). It has a very low inductance of only 0.5 μH, but this is enough to significantly reduce through-current pulses. The inductor is wound with stranded wire, with a total cross-section of at least 3 mm2 and has 6 turns wound on a 16 mm mandrel. It is filled with epoxy glue, since the stranded wire does not hold its shape. The throttle and its snubber circuit must be located in the fan blowing area.

The control unit, which is based on a voltage-controlled generator - VCO, which is part of the CD4046 microcircuit. And also the IR2104 driver, which converts the CD4046 single-phase signal into two anti-phase ones. The generator is manually controlled by voltage and changes the frequency in the range of 25-50 kHz. As the frequency changes, the power in the inductor changes. To make it easier to work with the inverter, a current limiting circuit has been introduced into the control board.

The secondary winding of the matching transformer consists of one turn of copper tube D 6mm. It is combined with a radiator for keys and has a single block design through which water is pumped. The pump is a car windshield washer pump.

The nodes in the photographs and videos may be slightly inconsistent, since there were three versions that did not differ significantly in circuit designs, but in general the design of all of them is similar. This design has been carefully worked out, I consider it the most compact and repairable.

The first simplest version was published on this forum Since then, a lot of water has passed under the bridge, and design solutions have changed. I tried it with PLL, the adjustment itself worked great, but overall I didn’t like it. Therefore, I settled on a “current limiting” circuit. All my research on this issue can be found herehttp://induction.lis...?p=19278#p19278 .

What exactly is the advantage of this version. The first version had a simple master oscillator, with the ability to control frequency. Its disadvantage is that you need to very accurately (using an oscilloscope) adjust the inductor to the inverter, or the inverter to the inductor. And if there are replaceable inductors, then they must have the same inductance. In principle, this is not so difficult, with some experience. But if the inductor is affected mechanically, accidentally, by compressing or stretching the turns, then such an inductor can no longer provide the power for which it was originally configured, and may even damage the inverter. The second version with PLL made it possible to change inductors without particularly thinking about its inductance. But there is one caveat. Such a device consumed maximum power with an unloaded inductor, and when you load the inductor, the power drops. In the end, the end result will be the same, but it will take two to three times longer to achieve. Increasing the heating time is always bad, but doubly so with surface hardening. More precisely, it is hardly possible. I had to look for a compromise. And I think I found it. Here's the diagram.

But there are minor improvements in the control unit, I gave up some bells and whistles, and most importantly, I moved the damping throttle to the power supply minus, this allowed me to place it and the snubber (structurally) closer to the fan, which improved its cooling.

Now how does it all work. Let's start, as always, with nutrition. The power supply at first glance looks archaic, but it has its advantages. Firstly, simplicity, secondly, the stabilizers have current protection, which helps protect the drivers in case of breakdown of power switches. I tried to use the “Return”, for such a power (50W), it turns out to be bulky, and it has a lot of disadvantages. I draw your attention to the inverter starting system. Instead of a traditional starting resistor, there is a capacitor C10 (MBGO), what is its advantage? Usually, when the keys break down, the starting resistor burns, but the capacitor can remain in this state for as long as desired. The moment the inverter is turned on to the network, the electrolytes of filter C2 begin to charge through this capacitor until the voltage across them reaches 200-250V, the power supply starts working, and when it starts working, the starting relay is attracted and the start occurs very smoothly, with a delay of 1-2 seconds. Also, if the keys break down, the power supply will first turn off, release the relay, and the inverter can remain in this position for as long as desired. Even the fuse or circuit breaker does not have time to operate. In turn, if there is no power, then the drivers remain intact.

Now a little about the tricky damping throttle Dr1. As I already wrote, the mode below resonance assumes through currents. What does this come from? Let's assume that VT1 has opened, the circuit is pumping, + Pit, VT1, TP1, Cut, Dr1, minus. The slice will charge faster than the VT1 key closes, and the process will go in the opposite direction, that is, the circuit will begin to release energy to the power source. Since our circuit reaction is capacitive, the voltage of the same polarity will charge C2 through the opposed diode VT1 (unfortunately, I forgot to draw it), but after some time VT2 will open, and a short circuit will result, through the still open opposed diode VT1 and the opening VT2. The short circuit is very short, tens to hundreds of nanoseconds, but the currents are prohibitive. To reduce them, Dr1 with a snobber chain serves. For a working cycle with a period of say 30 μs, the inductor has a low resistance, and for a through current of 50 ns it has a large resistance. In practice it looks like this. The operating current of the primary winding is 60A, and the through current is only 80A. This fits well with the parameters of the G4PC50UD, and many other IGBTs. In the absence of this choke, the current can be an order of magnitude greater, which also allows the switches to work in many cases. There seems to be nothing to talk about keys and drive faiths.

How the control unit works. I bought CD 4046, for five rubles, a “bunch”, when I was working on PLL, they remained unused, which gave me the idea to use a controlled voltage generator. I won’t write how it works, but I’ll briefly say that if a varying voltage is applied to the 9th leg, then the output frequency (3,4) will change proportionally. R11 and R6, set the frequency range, upper and lower, respectively. The frequency, as well as the power, can be changed manually, with resistor R2 - higher frequency - higher power. Comparator DA1/1 compares the voltage set by potentiometer R12 and the voltage from the CT, as soon as the CT voltage exceeds the reference, the comparator, with its output transistor, through VD1 and R4, begins to discharge the capacitance of the VCO filter C2, the voltage on it decreases, the frequency too, and the current drops primary winding. A negative OS is formed. Having set the rated operating current once, we configure the comparator for this current. It is not possible to increase the power further - it can only be reduced. When replacing an inductor with a different inductance, you can adjust the inverter for it in one motion. How does this happen? The VCO always starts operating from the lower frequency of the range, therefore, if the operating frequency of the inductor is within the specified frequency range, then the frequency will rest against the rated current we have specified, which corresponds to the rated power of the inductor. The frequency (power) setting resistor is turned until the comparator works, and they work in this position. The limitation is indicated by an LED. For this, the second half of the comparator DA1/2 is used.

I used a windshield washer pump for cooling. It is powered through a field switch (VT3), which allows you to control both it and the inverter with one pair of contacts. There are also ballast resistors (R18) in the pump circuit, which made it possible to reduce the current consumed by it to 2.5A, and its performance is quite sufficient. Some write that I cooled the transistors with water, because the transistors simply cannot withstand air cooling. Actually this is not true. It would be a sin not to use water cooling, since you can’t do without water, and besides, it makes the device compact.

A little about setup. Each power supply module and control unit must be checked and configured separately, preferably on the table from the power source. Check everything carefully, check it in different modes. When the entire inverter is assembled, 220V is supplied to the power supply, separately from the inverter (no power is supplied to the power part). They check the operation of the generator, then the operation of the drivers, by hanging the oscilloscope on the gates and emitters of the transistors. Check the operation of the pump. If everything is fine, turn on the power part (preferably first through the LATR), while the power supply is powered separately. They check the operation without the inductor for now. At the output, a meander with slightly rounded tops with a voltage of 15V can be loaded with some kind of lamp, such as from a headlight. Next, screw on the inductor, try with the inductor, still through LATR (80-100 volts). Start with the lower frequency. On the inductor, at first there is a torn sine wave, as the frequency increases, the sine wave becomes clean, 80-90 volts. In this mode, the comparator is configured. The notches on the sine wave are the moment when the keys are switched; they are very convenient for tuning the inverter. These notches should be located in the zone from the zero of the sinusoid to the top. The best option is somewhere in the middle. In limit mode, the inverter should not whistle.

Something like that. I probably missed something, but ten pages won’t be enough to write everything down. You can write about the details on any of the forums or directly here. At least three people repeated my inverter; others did not have enough knowledge or patience. Lastly, video.

Electric heating devices are extremely convenient to use. They are much safer than any gas equipment, do not produce soot and soot, unlike units operating on liquid or solid fuel, and finally, they do not require the preparation of firewood, etc. The main disadvantage of electric heaters is the high cost of electricity. In search of savings, some craftsmen decided to make an induction heater with their own hands. They received excellent equipment that requires much less expense to operate.

Working principle of induction heating

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

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

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

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

Induction heat generator in a heating system

To organize heating of a private house using an induction heater, the easiest way is to use a transformer, which consists of a primary and secondary short-circuited winding. Eddy currents in such a device arise in the internal component and direct the resulting electromagnetic field to the secondary circuit, which simultaneously serves as a housing and a heating element for the coolant.

Please note that not only water, but also antifreeze, oil and any other conductive media can act as a coolant during induction heating. In this case, the degree of purification of the coolant does not matter much.

The inverter heater is compact in size, operates silently and can be installed in almost any suitable location that meets safety requirements

Equipped with two pipes. The lower pipe, through which the cold coolant will flow, must be installed at the inlet section of the pipeline, and at the top, a pipe is installed that transfers the hot coolant to the supply section of the pipeline. When the coolant in the boiler heats up, hydrostatic pressure arises and enters the heating network.

There are a number of advantages to using an induction heater that should be mentioned:

• the coolant constantly circulates in the system, which prevents the possibility of overheating;
• the induction system vibrates, as a result, scale and other sediments are not deposited on the walls of the equipment;
• the absence of traditional heating elements allows the boiler to be operated at high intensity without fear of frequent breakdowns;
• the absence of detachable connections eliminates leaks;
• the operation of the induction boiler is not accompanied by noise, so it can be installed in almost any suitable room;
• During induction heating, no hazardous fuel decomposition products are released.

Safety, quiet operation, the ability to use a suitable coolant and the durability of the equipment have attracted many homeowners. Some of them are thinking about the possibility of making a homemade induction heater.

How to make an induction heater yourself?

Making such a heater yourself is not a very difficult task that even a novice craftsman can handle. To get started, you should stock up on:

• a piece of plastic pipe with thick walls, which will become the heater body;
• steel wire with a diameter of no more than 7 mm;
• adapters for connecting the heater body to the heating system of the house;
• a metal mesh that will hold pieces of steel wire inside the case;
• copper wire to create an induction coil;
• high frequency inverter.

First you need to prepare the steel wire. To do this, simply cut it into pieces about 5 cm long. The bottom of a piece of plastic pipe is covered with a metal mesh, pieces of wire are poured inside, and the top of the body is also covered with a metal mesh. The housing must be completely filled with pieces of wire. In this case, wire made not only from stainless steel, but also from other metals may be acceptable.

Then you should make an induction coil. A prepared plastic case is used as a base, onto which 90 turns of copper wire are carefully wound.

After the coil is ready, the housing is connected to the heating system of the house using adapters. After this, the coil is connected to the network through a high-frequency inverter. It is considered quite advisable to make an induction heater from a welding inverter, since this is the simplest and most cost-effective option.

Most often, in the manufacture of homemade vortex induction heaters, inexpensive models of welding inverters are used, since they are convenient and fully comply with the requirements

It should be noted that you should not test the device if no coolant is supplied to it, otherwise the plastic case may melt very quickly.

An interesting version of an induction heater made from a hob is presented in the video:

To increase the safety of the structure, it is recommended to insulate the exposed areas of the copper coil.

The induction heating system should be placed at a distance of at least 30 cm from walls and furniture and at least 80 cm from the ceiling or floor.

To make the operation of the device safer, it is recommended to equip it with a pressure gauge, as well as an automatic control system and devices for removing air trapped in the system.

Devices that heat using electricity rather than gas are safe and convenient. Such heaters do not produce soot or unpleasant odor, but consume a large amount of electricity. An excellent solution is to assemble an induction heater with your own hands. This both saves money and contributes to the family budget. There are many simple schemes according to which you can assemble an inductor yourself.

To make it easier to understand the circuits and correctly assemble the structure, it would be useful to look into the history of electricity. Methods for heating metal structures with electromagnetic coil current are widely used in the industrial production of household appliances - boilers, heaters and stoves. It turns out that you can make a working and durable induction heater with your own hands.

How the devices work

How the devices work

The famous 19th century British scientist Faraday spent 9 years researching to convert magnetic waves into electricity. In 1931, a discovery was finally made, called electromagnetic induction. The wire winding of the coil, in the center of which there is a core of magnetic metal, creates a magnetic field under the force of alternating current. Under the influence of vortex flows, the core heats up.

An important nuance is that heating will occur if the alternating current feeding the coil changes the vector and sign of the field at high frequencies.

Faraday's discovery began to be used both in industry and in the manufacture of homemade motors and electric heaters. The first smelter based on a vortex inductor was opened in 1928 in Sheffield. Later, factory workshops were heated using the same principle, and to heat water and metal surfaces, experts assembled an inductor with their own hands.

The device diagram of that time is still valid today. A classic example is an induction boiler, which contains:

• metal core;
• frame;
• thermal insulation.

Less weight, size and higher efficiency are achieved due to thin steel pipes that serve as the basis of the core. In kitchen tiles, the inductor is a flattened coil located near the hob.

The features of the circuit for accelerating the current frequency are as follows:

• industrial frequency of 50 Hz is not suitable for homemade devices;
• direct connection of the inductor to the network will lead to hum and low heating;
• effective heating is carried out at a frequency of 10 kHz.

Assembly according to diagrams

Anyone familiar with the laws of physics can assemble an inductive heater with their own hands. The complexity of the device will vary depending on the level of preparedness and experience of the master.

There are many video tutorials that you can follow to create an effective device. It is almost always necessary to use the following basic components:

• steel wire with a diameter of 6−7 mm;
• copper wire for the inductor;
• metal mesh (to hold the wire inside the housing);
• adapters;
• pipes for the body (plastic or steel);
• high frequency inverter.

This will be enough to assemble an induction coil with your own hands, and this is what is at the heart of the instantaneous water heater. After preparing the necessary elements You can approach the manufacturing process of the device directly:

• cut the wire into pieces of 6-7 cm;
• cover the inside of the pipe with a metal mesh and fill the wire to the top;
• similarly close the pipe hole from the outside;
• wind copper wire around the plastic body at least 90 times for a coil;
• insert the structure into the heating system;
• Using an inverter, connect the coil to electricity.

It is advisable to first ground the inverter and prepare antifreeze or water.

Using a similar algorithm, you can easily assemble an induction boiler, for which you should:

• cut blanks from a steel pipe 25 by 45 mm with a wall no thicker than 2 mm;
• weld them together, connecting them with smaller diameters;
• weld iron covers to the ends and drill holes for threaded pipes;
• make a mount for an induction stove by welding two corners on one side;
• insert the hob into the bracket from the corners and connect to the power supply;
• add coolant to the system and turn on the heating.

Many inductors operate at a power of no higher than 2 - 2.5 kW. Such heaters are designed for a room of 20 - 25 m². If the generator is used in a car service, you can connect it to a welding machine, but It is important to consider certain nuances:

• You need alternating current, not direct current like an inverter. The welding machine will have to be examined for the presence of points where the voltage does not have a direct direction.
• The number of turns to a larger cross-section wire is selected by mathematical calculation.
• Cooling of the operating elements will be required.

Creation of sophisticated devices

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

Design of HDTV installations

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

• connected to mains power.

• targeted electrical;
• connected to mains power.

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

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

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

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

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

Vortex heaters

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

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

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

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

Based on the diagrams, you can quickly assemble inductors of various powers for heating water, metals, heating a house, garage and car service center. It is also necessary to remember the safety rules for the effective service of heaters of this type, because a coolant leak from a homemade device can result in a fire.

There are certain conditions for organizing work:

• the distance between the induction boiler, walls, electrical appliances should be at least 40 cm, and it is better to retreat 1 m from the floor and ceiling;
• using a pressure gauge and an air release device, a safety system is provided behind the outlet pipe;
• It is advisable to use the devices in closed circuits with forced circulation of coolant;
• Can be used in plastic pipelines.

Self-assembly of induction generators will be inexpensive, but not free either, because you need components of fairly good quality. If a person does not have special knowledge and experience in radio engineering and welding, then you should not assemble a heater for a large area yourself, because the heating power will not exceed 2.5 kW.

However, self-assembly of an inductor can be considered as self-education and practical improvement of the home owner’s skills. You can start with small devices using simple circuits, and since the principle of operation in more complex devices is the same, only additional elements and frequency converters are added, it will be easy and quite affordable to master it step by step.

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