Bipolar transistors in induction heater circuits. Do-it-yourself induction heater: a description of the simplest scheme of a home-made device. We assemble an induction device with our own hands: important details

A domestic metal melting furnace can also be used to quickly heat up metal elements, for example, when they are tinned or shaped. The 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 generator sets - this way you can achieve their maximum efficiency.

Recently, there was a need to create a small do-it-yourself induction heater. Wandering around the Internet, I found several schemes for induction heaters. Many schemes did not suit because of the rather complicated strapping, 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 to act on the metal with Foucault currents. Such a heater is actively used in various fields of science and technology. In theory, Foucault currents are indifferent to the types and properties of metals, so the inductor can heat up or melt absolutely any metal.

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

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

It turned out to be a fairly powerful home-made induction heater (efficiency no more than 65%), on the basis of which even a small induction stove can be assembled. 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. Such a heater can melt wires with a diameter of 1.5 mm - I managed to do this in just 20 seconds, but at the same time, the high-voltage ET transistors got so hot that they could fry eggs on them!

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

The basis of the 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, it often becomes necessary to adjust the circuit to the resonance frequency, accurately calculate the number of turns and the diameter of the circuit wire, as well as count the circuit capacitor, but here all this is not there and the circuit works immediately).

The mains voltage (220 Volts) is first rectified by a diode rectifier, then fed to the circuit. The frequency is set by the dinistor (diac) of the DB3 brand. The circuit itself has no protections, only a limiting resistor at the power input, which supposedly should work as a mains fuse, but at the slightest problem, transistors fly out first. The reliability of the induction heater circuit can be improved by replacing the diodes in the rectifier with more powerful ones, adding a network filter to the input of the circuit and replacing the power transistors with more powerful ones, say MJE13009.

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

The modern and most economical device for heating water is an induction water heater. Unlike analogues, it is completely environmentally friendly, does not dry or burn out the air, and meets modern safety requirements. It can be used both as an instantaneous water heater and as a boiler for space heating. The device is usually bought in a store, we offer an alternative - self-production. In the latter case, the device may not have such an attractive appearance, but it will be much cheaper.

Pros and cons of induction devices for heating water

The device has a fairly simple design and does not require special documents allowing the use and installation. The induction water heater has a high degree of efficiency and optimum reliability for the user. When using it as a boiler for heating, you don’t even need to install a pump, since water flows through the pipes due to convection (when heated, the liquid practically turns into steam).

Also, the device has a number of advantages, which distinguishes it from other types of water heaters. So, induction heater:

In induction heaters, water becomes hot due to the pipe through which it flows, and the latter is heated due to the induction current created by the coil.

• much cheaper than their counterparts, such a device can be easily assembled independently;
• completely silent (although the coil vibrates during operation, this vibration is not noticeable to a person);
• vibrates during operation, due to which dirt and scale do not stick to its walls, and therefore does not need to be cleaned;
• has a heat generator that can be easily sealed due to the principle of operation: the coolant is inside the heating element and the energy is transferred to the heater through an electromagnetic field, no contacts are needed; therefore, sealing gum, seals and other elements that can quickly deteriorate or leak will not be needed;
• there is simply nothing to break in the heat generator, since the water is heated by an ordinary pipe, which is unable to deteriorate or burn out, unlike a heating element;

Do not forget that the maintenance of an induction heater will be much cheaper than a boiler or gas boiler. The device has a minimum of parts that almost never fail.

Despite the huge number of advantages, the induction water heater has a number of disadvantages:

• the first and most painful for the owners is the electricity bill; the device cannot be called economical, so you have to pay a decent amount of time for its use;
• secondly, the device gets very hot and heats up not only itself, but also the surrounding space, so it is better not to touch the body of the heat generator during its operation;
• third - the device has an extremely high efficiency and heat transfer, therefore, when using it be sure to install a temperature sensor, otherwise the system may explode.

Do-it-yourself induction water heater: diagram

The device is a transformer having two windings: primary and secondary. The first circuit converts electrical energy into eddy currents, thereby creating a directional induction field, which provides induction heating. On the secondary circuit, the converted energy is transferred to the coolant (in our case, it is water).

It is important to consider the type of material from which the winding is made. So, in household models, copper wire is most often used. Such material is well suited for heating water in boilers.

In addition to the transformer, the device has a generator and a pump (optional).

Scheme of a simple induction water heater. As you can see, the device has a fairly simple design and a small number of elements.

Units and parts of the heat generator

The device includes:

• an alternator that increases the frequency of the current;
• an inductor that transforms electricity into magnetic energy is a coil of copper wire;
• heating element, most often its role is played by a metal pipe.

Thanks to this design, energy transfer is carried out almost without loss. The efficiency reaches 98%.

Principle of operation

The induction water heater consists of a generator, a coil and a core, the latter is heated by electromagnetic energy.

The device converts electrical energy into electromagnetic energy. The latter, in turn, acts on the core (pipe), which heats up and transfers thermal energy to the water. All these energies are converted by an inductor consisting of a coil and a core. The generator is used to increase the frequency of the current, since it is difficult to achieve high heating with a standard frequency of 50 Hz.

In factory models, the current frequency reaches 1 kHz.

Do-it-yourself flowing induction water heater

Before proceeding with the installation, you need to stock up on the necessary parts. So, the best option would be a welding high-frequency inverter, a smoothly changing current range. Such a device will cost the least. A more expensive option would be a three-phase transformer, which is the AC power source for the water heater inductor. In this case, it is worth using a coil of 50-90 turns, and as a material, take copper wire with a diameter of 3 or more millimeters.

As a core, you can use both a metal and a polymer pipe along with a wire (it is used as a heating element). In the latter case, the thickness of the walls should not be less than 3 mm in order to calmly withstand high temperatures.

To assemble the water heater, you will need: wire cutters, screwdrivers, a soldering iron and a welding machine if a metal pipe is used.

Installation of an induction water heater

Wrap the pipe with copper wire, making about 90 turns.

There are many options for assembling the device. We suggest trying to assemble the device according to the following scheme:

1. Prepare the workplace, materials and tools.
2. Fix a small piece of polymer pipe (remember that the minimum wall thickness should be 3 mm).
3. Trim the ends of the core to leave 10 cm of spare wire for the taps.
4. Mount a corner on the lower outlet. In the future, the return from the heating should be connected here (if the heater is used as a boiler).
5. Lay the chopped wire tightly around the pipe. It is necessary to make at least 90 turns.
6. Install a tee on the top pipe through which hot water will exit.
7. Mount the protective circuit of the device. It can be made from both polymer and metal.
8. Connect copper wire to the water heater terminals, then fill the core with water.
9. Check the functionality of the inductor.

Recommendations. It is better to install ball valves on all outlets for convenience and ease of dismantling the water heater in the event of a breakdown. But it is not necessary to fill the pipe with metal pieces, since this does not give the desired effect. Do not forget to leave a window in the housing for access to the control panel of the welding machine.

Induction water heaters for heating

Heating circuit, where an induction boiler serves as a coolant heater.

Such a device has proven itself not only as an instantaneous water heater, but also as a boiler for heating. True, in this case, the welding machine as a generator is no longer suitable, you have to use a transformer with two windings. The latter transforms the eddy currents that occur on the primary winding into an electromagnetic field that is created on the secondary circuit.

In the heating system, the coolant can be not only water, but also oil or antifreeze. That is, any liquid that can conduct electricity.

The boiler from the induction water heater must be equipped with two pipes for hot and cold water. Cold water will flow from the bottom, it must be mounted on the inlet section of the line, and a branch pipe must be placed on top, which will supply hot water to the heating system. As a result, the circulation of water is carried out naturally under the influence of convection without a pump.

What you need to know about security

Do not forget that we are dealing with a source of increased danger - an electric heater, so when assembling and using it, you must follow some rules:

Be sure to use a separate electrical line to connect the induction boiler, and also equip it with a safety group.

1. If water circulates naturally in the boiler, then be sure to equip it with a temperature sensor so that the device turns off automatically when overheated.
2. Do not plug a homemade water heater into a power outlet; it is better to run a separate line for this with an increased cable cross section.
3. All exposed wires must be insulated to protect people from electric shock or burns.
4. Never turn on the inductor if the pipe is not filled with water. Otherwise, the pipe will melt, and the device will close, or it may even catch fire.
5. The device must be mounted at a height of 80 cm from the floor, but so that about 30 cm remains to the ceiling. Also, you should not install it in a residential area, since the electromagnetic field has a bad effect on people's health.
6. Don't forget to ground the inductor.
7. Be sure to connect the device through the machine so that in the event of an accident, the latter will turn off the power from the water heater.
8. A safety valve must be installed in the pipeline system, which will automatically reduce the pressure in the system.

Conclusion

The induction water heater has a high efficiency, can act as a boiler for the heating system, self-assembly and installation is also allowed, and its use is in no way regulated by the law of the Russian Federation. But still, before using it, it is worth weighing the pros and cons. Despite its high efficiency, the device consumes a large amount of energy, is considered unsafe (especially home-made) and has a bad effect on human health. Therefore, we recommend mounting the inductor in a private house or in the country.

Before we talk about how to assemble a homemade induction heater, you need to find out what it is and how it works.

History of induction heaters

In the period from 1822 to 1831, the famous English scientist Faraday conducted a series of experiments, the purpose of which was to achieve the conversion of magnetism into electrical energy. He spent a lot of time in his laboratory. Until one day, in 1831, Michael Faraday finally got his way. The scientist finally managed to get an electric current in the primary winding from a wire that was wound on an iron core. This is how electromagnetic induction was discovered.

Power of induction

This discovery began to be used in industry, in transformers, various motors and generators.

However, this discovery really became popular and necessary only after 70 years. During the rise and development of the metallurgical industry, new, modern methods of melting metals were required in the conditions of metallurgical production. By the way, the first foundry, which used a vortex induction heater, was launched in 1927. The plant was located in the small English town of Sheffield.

And in the tail and in the mane

In the 80s, the principle of induction was already being applied in full. Engineers were able to create heaters that worked on the same principle of induction as a metallurgical furnace for melting metals. Such devices heated the workshops of factories. A little later, household appliances began to be produced. And some craftsmen did not buy them, but assembled induction heaters with their own hands.

Operating principle

If you disassemble an induction type boiler, then there you will find a core, electrical and thermal insulation, then a body. The difference between this heater and those used in industry is the toroidal winding with copper conductors. It is located between two pipes welded together. These pipes are made of ferromagnetic steel. The wall of such a pipe is more than 10 mm. As a result of this design, the heater has a much lower weight, higher efficiency, as well as small dimensions. A pipe with a winding works here as a core. And the other serves directly to heat the coolant.

The induction current, which is generated by a high-frequency magnetic field from the external winding to the pipe, heats the coolant. This process causes the walls to vibrate. Due to this, scale is not deposited on them.

Heating occurs due to the fact that the core is heated during operation. Its temperature rises due to eddy currents. The latter are formed due to the magnetic field, which, in turn, is generated by high voltage currents. This is how an induction water heater and many modern boilers work.

DIY induction power

Heating appliances that use electricity as energy are as convenient and comfortable to use as possible. They are much safer than gas powered equipment. In addition, in this case there is neither soot nor soot.

One of the disadvantages of such a heater is the high consumption of electricity. In order to somehow save money, craftsmen learned how to assemble induction heaters with their own hands. The result is an excellent device that requires much less electrical energy to operate.

Manufacturing process

To make such a device yourself, you do not need to have serious knowledge in electrical engineering, and anyone can handle the assembly of the structure.

To do this, we need a piece of thick-walled plastic pipe. It will work as the body of our unit. Next, you need a steel wire with a diameter of not more than 7 mm. Also, if you need to connect the heater to the heating in the house or apartment, it is advisable to purchase adapters. You also need a metal mesh that should hold the steel wire inside the case. Naturally, copper wire is needed to create an inductor. Also, almost everyone in the garage has a high-frequency inverter. Well, in the private sector, such equipment can be found without difficulty. Surprisingly, you can make induction heaters with your own hands from improvised means at no special cost.

First you need to carry out preparatory work for the wire. We cut it into pieces 5-6 cm long. The bottom of the part of the pipe must be closed with a net, and pieces of cut wire should be poured inside. From above, the pipe must also be closed with a net. It is necessary to pour so much wire to fill the pipe from top to bottom.

When the part is ready, you need to install it in the heating system. Then you can connect the coil to electricity through the inverter. It is believed that an induction heater from an inverter is a very simple and most budgetary device.

Do not test the apparatus if there is no water or antifreeze supply. You just melt the pipe. Before starting this system, it is advisable to make a ground for the inverter.

Modern heater

This is the second option. It involves the use of products of modern electronic devices. Such an induction heater, the diagram of which is presented below, does not need to be adjusted.

This circuit implies the principle of series resonance and can develop decent power. If you use more powerful diodes and larger capacitors, you can increase the performance of the unit to a serious level.

Assembling the vortex induction heater

In order to assemble this device, you need a choke. It can be found if you open the power supply of a regular computer. Next, you need to wind a wire made of ferromagnetic steel, copper wire 1.5 mm. Depending on the required parameters, it may take from 10 to 30 turns. Then you need to pick up field effect transistors. They are selected based on the maximum open junction resistance. As for the diodes, they need to be taken under a reverse voltage of at least 500 V, while the current will be somewhere around 3-4 A. You will also need zener diodes rated for 15-18 V. And their power should be about 2-3 Tue Resistors - up to 0.5 W.

Next, you need to assemble the circuit and make a coil. This is the basis on which the entire VIN induction heater is based. The coil will consist of 6-7 turns of 1.5 mm copper wire. Then the part must be included in the circuit and connected to electricity.

The device is able to heat the bolts to yellow. The circuit is extremely simple, however, the system generates a lot of heat in operation, so it is better to install radiators on transistors.

More complex design

In order to assemble this unit, you need to be able to work with welding, and a three-phase transformer is also useful. The design is presented in the form of two pipes that must be welded into each other. At the same time, they will play the role of a core and a heater. The winding is wound on the body. Thus, you can significantly increase productivity while achieving small overall dimensions and low weight.

To perform the supply and removal of the coolant, it is necessary to weld two pipes into the device body.

It is recommended that in order to eliminate possible heat losses as much as possible, as well as to protect yourself from possible current leaks, make insulation for the boiler. It will eliminate the occurrence of excessive noise, especially during intensive work.

It is desirable to use such systems in closed heating circuits in which there is a forced circulation of the coolant. It is allowed to use such units for plastic pipelines. The boiler must be installed in such a way that the distance between it and walls and other electrical appliances is at least 30 cm. It is also desirable to keep a distance of 80 cm from the floor and ceiling. It is also recommended to install a security system behind the outlet pipe. For this, a pressure gauge, an air release device, as well as a blast valve are suitable.

This is how easy and inexpensive you can assemble induction heaters with your own hands. This equipment may well serve you for many years and heat your home.

So, we found out how an induction heater is made with our own hands. The assembly scheme is not very complicated, so you can handle it in a matter of hours.