Induction heater. High-frequency induction plasma torch Video of operation of induction mid-frequency heaters

Induction heating is a method of non-contact heating with high frequency currents (RFH - radio-frequency heating, heating by radio frequency waves) of electrically conductive materials.

Description of the method.

Induction heating is the heating of materials by electric currents that are induced by an alternating magnetic field. Consequently, this is the heating of products made of conductive materials (conductors) by the magnetic field of inductors (sources of alternating magnetic field). Induction heating is carried out as follows. An electrically conductive (metal, graphite) workpiece is placed in a so-called inductor, which is one or several turns of wire (most often copper). Powerful currents of various frequencies (from tens of Hz to several MHz) are induced in the inductor using a special generator, as a result of which an electromagnetic field appears around the inductor. The electromagnetic field induces eddy currents in the workpiece. Eddy currents heat the workpiece under the influence of Joule heat (see Joule-Lenz law).

The inductor-blank system is a coreless transformer in which the inductor is the primary winding. The workpiece is the secondary winding, short-circuited. The magnetic flux between the windings is closed through the air.

At high frequencies, eddy currents are displaced by the magnetic field they themselves generate into thin surface layers of the workpiece Δ ​​(Surface effect), as a result of which their density increases sharply, and the workpiece heats up. The underlying layers of metal are heated due to thermal conductivity. It is not the current that is important, but the high current density. In the skin layer Δ, the current density decreases by e times relative to the current density on the surface of the workpiece, while 86.4% of the heat is released in the skin layer (of the total heat release. The depth of the skin layer depends on the radiation frequency: the higher the frequency, the thinner skin layer. It also depends on the relative magnetic permeability μ of the workpiece material.

For iron, cobalt, nickel and magnetic alloys at temperatures below the Curie point, μ has a value from several hundred to tens of thousands. For other materials (melts, non-ferrous metals, liquid low-melting eutectics, graphite, electrolytes, electrically conductive ceramics, etc.) μ is approximately equal to unity.

For example, at a frequency of 2 MHz, the skin depth for copper is about 0.25 mm, for iron ≈ 0.001 mm.

The inductor becomes very hot during operation, as it absorbs its own radiation. In addition, it absorbs thermal radiation from the hot workpiece. Inductors are made from copper tubes cooled by water. Water is supplied by suction - this ensures safety in the event of a burn-through or other depressurization of the inductor.

Application:
Ultra-clean non-contact melting, soldering and welding of metal.
Obtaining prototypes of alloys.
Bending and heat treatment of machine parts.
Jewelry making.
Processing of small parts that can be damaged by gas flame or arc heating.
Surface hardening.
Hardening and heat treatment of parts with complex shapes.
Disinfection of medical instruments.

Advantages.

High-speed heating or melting of any electrically conductive material.

Heating is possible in a protective gas atmosphere, in an oxidizing (or reducing) environment, in a non-conducting liquid, or in a vacuum.

Heating through the walls of a protective chamber made of glass, cement, plastics, wood - these materials absorb electromagnetic radiation very weakly and remain cold during operation of the installation. Only electrically conductive material is heated - metal (including molten), carbon, conductive ceramics, electrolytes, liquid metals, etc.

Due to the MHD forces that arise, intensive mixing of the liquid metal occurs, up to keeping it suspended in air or a protective gas - this is how ultra-pure alloys are obtained in small quantities (levitation melting, melting in an electromagnetic crucible).

Since heating is carried out through electromagnetic radiation, there is no contamination of the workpiece with torch combustion products in the case of gas-flame heating, or with the electrode material in the case of arc heating. Placing samples in an inert gas atmosphere and high heating rates will eliminate scale formation.

Ease of use due to the small size of the inductor.

The inductor can be made of a special shape - this will allow it to be evenly heated over the entire surface of parts of a complex configuration, without leading to their warping or local non-heating.

It is easy to carry out local and selective heating.

Since the most intense heating occurs in the thin upper layers of the workpiece, and the underlying layers are heated more gently due to thermal conductivity, the method is ideal for surface hardening of parts (the core remains viscous).

Easy automation of equipment - heating and cooling cycles, temperature adjustment and maintenance, feeding and removal of workpieces.

Induction heating units:

For installations with an operating frequency of up to 300 kHz, inverters based on IGBT assemblies or MOSFET transistors are used. Such installations are designed for heating large parts. To heat small parts, high frequencies are used (up to 5 MHz, medium and short wave range), high-frequency installations are built on vacuum tubes.

Also, to heat small parts, high-frequency installations are being built using MOSFET transistors for operating frequencies up to 1.7 MHz. Controlling transistors and protecting them at higher frequencies presents certain difficulties, so higher frequency settings are still quite expensive.

The inductor for heating small parts is small in size and has low inductance, which leads to a decrease in the quality factor of the working oscillatory circuit at low frequencies and a decrease in efficiency, and also poses a danger to the master oscillator (the quality factor of the oscillatory circuit is proportional to L/C, an oscillatory circuit with a low quality factor is too good “pumped” with energy, forms a short circuit in the inductor and disables the master oscillator). To increase the quality factor of the oscillatory circuit, two ways are used:
- increasing the operating frequency, which leads to more complex and expensive installations;
- use of ferromagnetic inserts in the inductor; pasting the inductor with panels made of ferromagnetic material.

Since the inductor operates most efficiently at high frequencies, induction heating received industrial application after the development and start of production of high-power generator lamps. Before World War I, induction heating had limited use. High-frequency machine generators (works by V.P. Vologdin) or spark-discharge installations were then used as generators.

The generator circuit can, in principle, be anything (multivibrator, RC generator, generator with independent excitation, various relaxation generators), operating on a load in the form of an inductor coil and having sufficient power. It is also necessary that the oscillation frequency be high enough.

For example, to “cut” a steel wire with a diameter of 4 mm in a few seconds, an oscillatory power of at least 2 kW is required at a frequency of at least 300 kHz.

The scheme is selected according to the following criteria: reliability; vibration stability; stability of the power released in the workpiece; ease of manufacture; ease of setup; minimum number of parts to reduce cost; the use of parts that together result in a reduction in weight and dimensions, etc.

For many decades, an inductive three-point generator (Hartley generator, generator with autotransformer feedback, circuit based on an inductive loop voltage divider) has been used as a generator of high-frequency oscillations. This is a self-exciting parallel power supply circuit for the anode and a frequency-selective circuit made on an oscillating circuit. It has been successfully used and continues to be used in laboratories, jewelry workshops, industrial enterprises, as well as in amateur practice. For example, during the Second World War, surface hardening of the T-34 tank rollers was carried out on such installations.

Disadvantages of three points:

Low efficiency (less than 40% when using a lamp).

A strong frequency deviation at the time of heating of workpieces made of magnetic materials above the Curie point (≈700C) (μ changes), which changes the depth of the skin layer and unpredictably changes the heat treatment mode. When heat treating critical parts, this may be unacceptable. Also, powerful HDTV installations must operate in a narrow range of frequencies permitted by Rossvyazohrankultura, since with poor shielding they are actually radio transmitters and can interfere with television and radio broadcasting, coastal and rescue services.

When changing workpieces (for example, a smaller one to a larger one), the inductance of the inductor-workpiece system changes, which also leads to a change in the frequency and depth of the skin layer.

When changing single-turn inductors to multi-turn ones, to larger or smaller ones, the frequency also changes.

Under the leadership of Babat, Lozinsky and other scientists, two- and three-circuit generator circuits were developed that have a higher efficiency (up to 70%) and also better maintain the operating frequency. The principle of their operation is as follows. Due to the use of coupled circuits and weakening of the connection between them, a change in the inductance of the operating circuit does not entail a strong change in the frequency of the frequency-setting circuit. Radio transmitters are designed using the same principle.

Modern HDTV generators are inverters based on IGBT assemblies or high-power MOSFET transistors, usually made according to a bridge or half-bridge circuit. Operate at frequencies up to 500 kHz. The transistor gates are opened using a microcontroller control system. The control system, depending on the task at hand, allows you to automatically hold

A) constant frequency
b) constant power released in the workpiece
c) the highest possible efficiency.

For example, when a magnetic material is heated above the Curie point, the thickness of the skin layer increases sharply, the current density drops, and the workpiece begins to heat up worse. The magnetic properties of the material also disappear and the process of magnetization reversal stops - the workpiece begins to heat up worse, the load resistance decreases abruptly - this can lead to “spreading” of the generator and its failure. The control system monitors the transition through the Curie point and automatically increases the frequency when the load abruptly decreases (or reduces power).

Notes.

If possible, the inductor should be located as close to the workpiece as possible. This not only increases the electromagnetic field density near the workpiece (proportional to the square of the distance), but also increases the power factor Cos(φ).

Increasing the frequency sharply reduces the power factor (proportional to the cube of the frequency).

When heating magnetic materials, additional heat is also released due to magnetization reversal; heating them to the Curie point is much more efficient.

When calculating an inductor, it is necessary to take into account the inductance of the buses leading to the inductor, which can be much greater than the inductance of the inductor itself (if the inductor is made in the form of one turn of small diameter or even part of a turn - an arc).

There are two cases of resonance in oscillatory circuits: voltage resonance and current resonance.
Parallel oscillatory circuit – current resonance.
In this case, the voltage on the coil and on the capacitor is the same as that of the generator. At resonance, the circuit resistance between the branching points becomes maximum, and the current (I total) through the load resistance Rн will be minimal (the current inside the circuit I-1l and I-2s is greater than the generator current).

Ideally, the loop impedance is infinity—the circuit draws no current from the source. When the generator frequency changes in any direction from the resonant frequency, the circuit impedance decreases and the line current (I total) increases.

Series oscillatory circuit – voltage resonance.

The main feature of a series resonant circuit is that its impedance is minimal at resonance. (ZL + ZC – minimum). When tuning the frequency above or below the resonant frequency, the impedance increases.
Conclusion:
In a parallel circuit at resonance, the current through the circuit terminals is 0 and the voltage is maximum.
In a series circuit, on the contrary, the voltage tends to zero and the current is maximum.

The article was taken from the website http://dic.academic.ru/ and revised into a text more understandable for the reader by the company Prominductor LLC.

And in devices, heat in the heated device is released by currents arising in the alternating electromagnetic field inside the unit. They are called induction. As a result of their action, the temperature increases. Induction heating of metals is based on two main physical laws:

• Faraday-Maxwell;
• Joule-Lenz.

In metal bodies, when they are placed in an alternating field, vortex electric fields begin to arise.

Induction heating device

Everything happens as follows. Under the influence of a variable, the electromotive force (EMF) of induction changes.

EMF acts in such a way that eddy currents flow inside bodies, which release heat in full accordance with the Joule-Lenz law. EMF also generates alternating current in the metal. In this case, thermal energy is released, which leads to an increase in the temperature of the metal.

This type of heating is the simplest, as it is non-contact. It allows you to reach very high temperatures at which you can process

To provide induction heating, it is necessary to create a certain voltage and frequency in electromagnetic fields. This can be done in a special device - an inductor. It is powered from an industrial network at 50 Hz. You can use individual power sources for this - converters and generators.

The simplest device for a low-frequency inductor is a spiral (insulated conductor), which can be placed inside a metal pipe or wound around it. Passing currents heat the pipe, which in turn transfers heat to the environment.

The use of induction heating at low frequencies is quite rare. Metal processing at medium and high frequencies is more common.

Such devices are distinguished by the fact that the magnetic wave hits the surface, where it is attenuated. The body converts the energy of this wave into heat. To achieve maximum effect, both components must be close in shape.

Where are they used?

The use of induction heating is widespread in the modern world. Area of ​​use:

• melting of metals, their soldering using a non-contact method;
• obtaining new metal alloys;
• mechanical engineering;
• jewelry making;
• manufacturing small parts that may be damaged when using other methods;
• (and the parts can be of the most complex configuration);
• heat treatment (processing of machine parts, hardened surfaces);
• medicine (disinfection of devices and instruments).

Induction heating: positive characteristics

This method has many advantages:

• With its help, you can quickly heat and melt any current-conducting material.
• Allows heating in any environment: in a vacuum, atmosphere, non-conducting liquid.
• Due to the fact that only the conductive material is heated, the walls, which weakly absorb waves, remain cold.
• In specialized areas of metallurgy, production of ultra-pure alloys. This is an interesting process, because the metals are mixed in a shell of protective gas.

• Compared to other types, induction does not pollute the environment. If in the case of gas burners contamination is present, just as in arc heating, then induction eliminates this due to “pure” electromagnetic radiation.
• Small dimensions of the inductor device.
• The ability to manufacture an inductor of any shape; this will not lead to local heating, but will promote uniform heat distribution.
• Indispensable if it is necessary to heat only a certain area of ​​the surface.
• It is not difficult to configure such equipment to the desired mode and regulate it.

Flaws

The system has the following disadvantages:

• It is quite difficult to independently install and adjust the type of heating (induction) and its equipment. It's better to contact specialists.
• The need to accurately match the inductor and the workpiece, otherwise induction heating will be insufficient, its power can reach low values.

Heating with induction equipment

To arrange individual heating, you can consider an option such as induction heating.

The unit will be a transformer consisting of windings of two types: primary and secondary (which, in turn, is short-circuited).

How does it work

The operating principle of a conventional inductor: vortex flows pass inside and direct the electric field to the second body.

In order for water to pass through such a boiler, two pipes are connected to it: for the cold water that comes in, and at the outlet of warm water - the second pipe. Due to pressure, water constantly circulates, which eliminates the possibility of heating the inductor element. The presence of scale is excluded here, since constant vibrations occur in the inductor.

Such an element will be inexpensive to maintain. The main advantage is that the device operates silently. It can be installed in any room.

Making equipment yourself

Installing induction heating is not very difficult. Even someone who has no experience will cope with the task after careful study. Before you start, you need to stock up on the following necessary items:

• Inverter. It can be used from a welding machine, is inexpensive and will have the high frequency required. You can make it yourself. But this is a time-consuming activity.
• Heater body (a piece of plastic pipe is suitable for this; induction heating of the pipe in this case will be the most effective).
• Material (wire with a diameter of no more than seven millimeters will do).
• Devices for connecting the inductor to the heating network.
• Mesh for holding the wire inside the inductor.
• An induction coil can be made from (it must be enameled).
• Pump (to supply water to the inductor).

Rules for making equipment yourself

In order for the induction heating installation to work correctly, the current for such a product must correspond to the power (it must be at least 15 amperes, if required, more).

• The wire should be cut into pieces no larger than five centimeters. This is necessary for efficient heating in a high-frequency field.
• The body must be no smaller in diameter than the prepared wire and have thick walls.
• For attachment to the heating network, a special adapter is attached to one side of the structure.
• A mesh should be placed at the bottom of the pipe to prevent the wire from falling out.
• The latter is needed in such quantity that it fills the entire internal space.
• The structure is closed and the adapter is installed.
• Then a coil is constructed from this pipe. To do this, wrap it with already prepared wire. The number of turns must be observed: minimum 80, maximum 90.
• After connecting to the heating system, water is poured into the device. The coil is connected to the prepared inverter.
• A water supply pump is installed.
• A temperature regulator is installed.

Thus, the calculation of induction heating will depend on the following parameters: length, diameter, temperature and processing time. Pay attention to the inductance of the buses leading to the inductor, which can be much greater than the inductor itself.

About hobs

Another application in household use, in addition to the heating system, is found in this type of heating in stove hobs.

This surface looks like a regular transformer. Its coil is hidden under the surface of the panel, which can be glass or ceramic. Current passes through it. This is the first part of the coil. But the second is the dishes in which the food will be cooked. Eddy currents are created at the bottom of the cookware. They heat the dishes first, and then the food in them.

Heat will only be released when dishes are placed on the surface of the panel.

If it is missing, no action occurs. The induction heating zone will correspond to the diameter of the cookware placed on it.

For such stoves you need special dishes. Most ferromagnetic metals can interact with the induction field: aluminum, stainless and enameled steel, cast iron. The only ones not suitable for such surfaces are: copper, ceramic, glass and utensils made from non-ferromagnetic metals.

Naturally, it will turn on only when suitable dishes are installed on it.

Modern stoves are equipped with an electronic control unit, which allows you to recognize empty and unsuitable cookware. The main advantages of cookers are: safety, ease of cleaning, speed, efficiency, and cost-effectiveness. You should never get burned on the surface of the panel.

So, we found out where this type of heating (induction) is used.

The main feature of induction heating is the conversion of electrical energy into heat using an alternating magnetic flux, i.e. inductively. If an alternating electric current I is passed through a cylindrical spiral coil (inductor), then an alternating magnetic field F m is formed around the coil, as shown in Fig. 1-17, c. The magnetic flux density is greatest inside the coil. When a metal conductor is placed in the cavity of the inductor, an electromotive force arises in the material, the instantaneous value of which is equal to:

Under the influence of emf. in a metal placed in a rapidly alternating magnetic field, an electric current arises, the magnitude of which depends primarily on the magnitude of the magnetic flux crossing the contour of the heated material, and the frequency of the current f, forming the magnetic flux.

Heat release during induction heating occurs directly in the volume of the heated material, and most of the heat is released in the surface layers of the heated part (surface effect). The thickness of the layer in which the most active heat release occurs is:

where ρ is resistivity, ohm*cm; μ - relative magnetic permeability of the material; f - frequency, Hz.

From the above formula it can be seen that the thickness of the active layer (penetration depth) decreases for a given metal with increasing frequency. The choice of frequency depends mainly on the technological requirements. For example, when melting metals, a frequency of 50 - 2500 Hz will be required, when heating - up to 10,000 Hz, when surface hardening - 30,000 Hz or more.

When melting cast iron, industrial frequency (50 Hz) is used, which makes it possible to increase the overall efficiency. installations, since energy losses due to frequency conversion are eliminated.

Induction heating is high-speed, since heat is released directly into the thickness of the heated metal, which allows metal to be melted in induction electric furnaces 2-3 times faster than in reflective flame furnaces.

Heating using high frequency currents can be carried out in any atmosphere; induction thermal units do not require time to warm up and are easily integrated into automatic and production lines. Using induction heating, temperatures up to 3000 °C or more can be achieved.

Due to its advantages, high-frequency heating is widely used in the metallurgical, mechanical engineering and metalworking industries, where it is used for melting metal, heat treatment of parts, heating for stamping, etc.

OPERATING PRINCIPLE OF INDUCTION OVEN. PRINCIPLE OF INDUCTION HEATING

The principle of induction heating is to convert the electromagnetic field energy absorbed by an electrically conductive heated object into thermal energy.

In induction heating installations, the electromagnetic field is created by an inductor, which is a multi-turn cylindrical coil (solenoid). An alternating electric current is passed through the inductor, resulting in a time-varying alternating magnetic field around the inductor. This is the first transformation of electromagnetic field energy, described by Maxwell's first equation.

The heated object is placed inside or next to the inductor. The changing (in time) flux of the magnetic induction vector created by the inductor penetrates the heated object and induces an electric field. The electric lines of this field are located in a plane perpendicular to the direction of the magnetic flux and are closed, that is, the electric field in the heated object is of a vortex nature. Under the influence of an electric field, according to Ohm's law, conduction currents (eddy currents) arise. This is the second transformation of electromagnetic field energy, described by Maxwell's second equation.

In a heated object, the energy of the induced alternating electric field irreversibly transforms into thermal energy. Such thermal dissipation of energy, resulting in heating of the object, is determined by the existence of conduction currents (eddy currents). This is the third transformation of the energy of the electromagnetic field, and the energy relationship of this transformation is described by the Lenz-Joule law.

The described transformations of electromagnetic field energy make it possible:
1) transfer the electrical energy of the inductor to the heated object without resorting to contacts (unlike resistance furnaces)
2) release heat directly in the heated object (the so-called “furnace with an internal heating source” according to the terminology of Prof. N.V. Okorokov), as a result of which the use of thermal energy is the most perfect and the heating rate increases significantly (compared to the so-called " ovens with an external heating source").

The magnitude of the electric field strength in a heated object is influenced by two factors: the magnitude of the magnetic flux, i.e., the number of magnetic lines of force piercing the object (or coupled with the heated object), and the frequency of the supply current, i.e., the frequency of changes (over time ) magnetic flux coupled with a heated object.

This makes it possible to create two types of induction heating installations, which differ in design and operational properties: induction installations with and without a core.

According to the technological purpose, induction heating installations are divided into melting furnaces for melting metals and heating installations for heat treatment (hardening, tempering), for through heating of workpieces before plastic deformation (forging, stamping), for welding, soldering and surfacing, for chemical-thermal treatment products, etc.

According to the frequency of changes in the current supplying the induction heating installation, they are distinguished:
1) industrial frequency installations (50 Hz), powered from the network directly or through step-down transformers;
2) high-frequency installations (500-10000 Hz), powered by electrical machine or semiconductor frequency converters;
3) high-frequency installations (66,000-440,000 Hz and above), powered by tube electronic generators.

The invention relates to electrical engineering and is aimed at increasing the service life of RF plasma torches and increasing their thermal efficiency. The problem is solved by the fact that the HF plasma torch contains a cylindrical discharge chamber made in the form of water-cooled longitudinal profiled metal sections placed in a protective dielectric casing, an inductor covering the casing, and input units for the main and thermal protective gases installed inside the discharge chamber at its end part. The thermal protective gas input unit is made in the form of one or more coaxial annular rows of longitudinal metal tubes with a number in each row equal to the number of longitudinal profiled metal sections. The tubes on the inductor side have a profiled gap for gas outlet, as well as a longitudinal gap relative to adjacent tubes in a row to a distance of at least one internal diameter of the discharge chamber, counting from the nearest turn of the inductor. The tubes are connected along the side surface by soldering or welding with radially located longitudinal metal tubes of the adjacent coaxial ring row, and the longitudinal metal tubes of the row closest to the longitudinal profiled metal sections are connected along the side surface to the adjacent section by soldering or welding. The main gas input unit on the inductor side is equipped with a diaphragm located at a distance of at least one internal diameter of the discharge chamber from the nearest turn of the inductor and having at least one hole for gas passage. The ends of the longitudinal metal tubes for the gas outlet in each row are located outside the inductor zone and are equidistant from its nearest turn, and the distance of the ends of the longitudinal metal tubes for the gas outlet from the nearest turn of the inductor increases with the distance of the coaxial ring row from the longitudinal profiled metal sections. Longitudinal metal tubes are located on the surface of adjacent, radially located longitudinal metal tubes, and the longitudinal metal tubes of the coaxial annular row closest to the longitudinal profiled metal sections are located on the surface of adjacent sections. The diaphragm on the inductor side forms an annular gap for the passage of gas with the longitudinal metal tubes of the nearest coaxial ring row, and the height of the annular gap for the passage of gas is made less than the height of the profiled gap for the gas outlet of the longitudinal metal tubes of the nearest coaxial ring row. The use of the proposed design of an RF plasma torch as a generator of low-temperature plasma in jet-plasma processes for processing dispersed materials has made it possible to create effective plasma reactor devices for opening finely ground ore raw materials, spheroidizing dispersed materials and obtaining highly dispersed oxide powders by generating untwisted plasma jets at the thermal efficiency of the RFI- plasma torches more than 80%. 15 salary f-ly, 5 ill.

INDUCTION HEATER- it's electric heater, operating when changing the flux of magnetic induction in a closed conducting loop. This phenomenon is called electromagnetic induction. Want to know how an induction heater works? ZAVODRR is a trade information portal where you will find information about heaters.

Vortex induction heaters

An induction coil is capable of heating any metal, heaters are assembled using transistors and have a high efficiency of more than 95%; they have long replaced lamp induction heaters, whose efficiency did not exceed 60%.

A vortex induction heater for non-contact heating has no losses in adjusting the resonant coincidence of the operating parameters of the installation with the parameters of the output oscillatory circuit. Vortex-type heaters assembled on transistors are able to perfectly analyze and adjust the output frequency in automatic mode.

Metal induction heaters

Heaters for induction heating of metal have a non-contact method due to the action of a vortex field. Different types of heaters penetrate the metal to a certain depth from 0.1 to 10 cm, depending on the selected frequency:

• high frequency;
• average frequency;
• ultra high frequency.

Metal induction heaters allow you to process parts not only in open areas, but also to place heated objects in isolated chambers in which you can create any environment, as well as a vacuum.

Electric Induction Heater

High Frequency Electric Induction Heater Every day it acquires new ways of application. The heater operates on alternating electric current. Most often, induction electric heaters are used to bring metals to the required temperatures during the following operations: forging, soldering, welding, bending, hardening, etc. Electric induction heaters operate at a high frequency of 30-100 kHz and are used to heat various types of media and coolants.

Electric heater used in many areas:

• metallurgical (HDTV heaters, induction furnaces);
• instrument making (soldering of elements);
• medical (production and disinfection of instruments);
• jewelry (jewelry manufacturing);
• housing and communal services (induction heating boilers);
• food (induction steam boilers).

Medium Frequency Induction Heaters

When deeper heating is required, medium-frequency type induction heaters are used, operating at medium frequencies from 1 to 20 kHz. Compact inductors for all types of heaters come in a variety of shapes, which are selected so as to ensure uniform heating of samples of the most varied shapes, while it is also possible to carry out specified local heating. The mid-frequency type will process materials for forging and hardening, as well as through heating for stamping.

Easy to operate, with an efficiency of up to 100%, induction mid-frequency heaters are used for a wide range of technologies in metallurgy (also for melting various metals), mechanical engineering, instrument making and other fields.

High Frequency Induction Heaters

The widest range of applications is for high-frequency induction heaters. The heaters are characterized by a high frequency of 30-100 kHz and a wide power range of 15-160 kW. The high-frequency type provides shallow heating, but this is enough to improve the chemical properties of the metal.

High-frequency induction heaters are easy to operate and economical, and their efficiency can reach 95%. All types operate continuously for a long time, and the two-block version (when the high-frequency transformer is placed in a separate block) allows round-the-clock operation. The heater has 28 types of protection, each of which is responsible for its own function. Example: monitoring water pressure in a cooling system.

Ultra High Frequency Induction Heaters

Microwave induction heaters operate at superfrequencies (100-1.5 MHz) and penetrate to a heating depth (up to 1 mm). The ultra-high-frequency type is indispensable for processing thin, small, small-diameter parts. The use of such heaters allows one to avoid unwanted deformations associated with heating.

Ultra-high-frequency induction heaters based on JGBT modules and MOSFET transistors have power limits of 3.5-500 kW. They are used in electronics, in the production of high-precision instruments, watches, jewelry, for the production of wire and for other purposes requiring special precision and filigree.

Forge induction heaters

The main purpose of forging-type induction heaters (IH) is heating of parts or parts thereof, prior to subsequent forging. Blanks can be of different types, alloys and shapes. Induction forging heaters allow you to process cylindrical workpieces of any diameter in automatic mode:

• economical, as they only take a few seconds to heat up and have a high efficiency of up to 95%;
• easy to use, allow for: full process control, semi-automatic loading and unloading. There are options with full automation;
• are reliable and can work continuously for a long time.

Induction shaft heaters

Induction heaters for hardening shafts work together with the hardening complex. The workpiece is in a vertical position and rotates inside a stationary inductor. The heater allows the use of all types of shafts for consistent local heating; the hardening depth can be fractions of millimeters in depth.

As a result of induction heating of the shaft along its entire length with instant cooling, its strength and durability increases many times over.

Induction pipe heaters

All types of pipes can be treated with induction heaters. The heater for pipes can be air- or water-cooled, with a power of 10-250 kW, with the following parameters:

• Air Cooled Tube Induction Heating produced using a flexible inductor and a thermal blanket. Heating temperature up to temperature 400 °C, and use pipes with a diameter of 20 - 1250 mm with any wall thickness.
• Induction heating water cooled pipe has a heating temperature of 1600 °C and is used for “bending” pipes with a diameter of 20 - 1250 mm.

Each heat treatment option is used to improve the quality of any steel pipe.

Pyrometer for heating control

One of the most important operating parameters of induction heaters is temperature. For more careful monitoring of it, in addition to built-in sensors, infrared pyrometers are often used. These optical devices allow you to quickly and easily determine the temperature of hard-to-reach (due to high heat, the possibility of exposure to electricity, etc.) surfaces.

If you connect a pyrometer to an induction heater, you can not only monitor the temperature, but also automatically maintain the heating temperature for a specified time.

Operating principle of induction heaters

During operation, a magnetic field is formed in the inductor, into which the part is placed. Depending on the task (depth of heating) and the part (composition), the frequency is selected; it can be from 0.5 to 700 kHz.

The principle of operation of the heater according to the laws of physics states: when a conductor is in an alternating electromagnetic field, an EMF (electromotive force) is formed in it. The amplitude graph shows that it moves proportionally to the change in the speed of the magnetic flux. Due to this, eddy currents are formed in the circuit, the magnitude of which depends on the resistance (material) of the conductor. According to the Joule-Lenz law, current leads to heating of a conductor that has resistance.

The operating principle of all types of induction heaters is similar to a transformer. The conductive workpiece, which is located in the inductor, is similar to a transformer (without a magnetic core). The primary winding is an inductor, the secondary inductance of the part, and the load is the metal resistance. During high-frequency heating, a “skin effect” is formed; eddy currents that form inside the workpiece displace the main current onto the surface of the conductor, because the heating of the metal on the surface is stronger than inside.

Advantages of induction heaters

An induction heater has undoubted advantages and is a leader among all types of devices. This advantage is as follows:

• It consumes less electricity and does not pollute the surrounding space.
• Easy to use, it provides high quality work and allows you to control the process.
• Heating through the walls of the chamber ensures special purity and the ability to obtain ultra-pure alloys, while melting can be carried out in different atmospheres, including inert gases and vacuum.
• With its help, it is possible to uniformly heat parts of any shape or selective heating
• Finally, induction heaters are universal, which allows them to be used everywhere, displacing outdated energy-consuming and inefficient installations.

Repair of induction heaters is carried out using spare parts from our warehouse. At the moment we can repair all types of heaters. Induction heaters are quite reliable if you strictly follow the operating instructions and do not allow excessive operating conditions - first of all, monitor the temperature and proper water cooling.

The subtleties of operation of all types of induction heaters are often not fully published in the manufacturers' documentation; their repairs should be carried out by qualified specialists who are well acquainted with the detailed operating principle of such equipment.

Video of induction mid-frequency heaters working

You can watch a video of the operation of a mid-frequency induction heater. The mid-frequency is used for deep penetration into all types of metal products. A medium-frequency heater is a reliable and modern equipment that works around the clock for the benefit of your enterprise.