In induction furnaces and devices, heat in a heated device is generated by currents that occur in an alternating electromagnetic field inside the unit. They are called induction. As a result of their action, an increase in temperature occurs. Induction heating of metals is based on two main physical laws:
- Faraday Maxwell
- Joule-Lenz.
In metallic bodies, when placed in an alternating field, vortex electric fields begin to appear.
Induction heating device
Everything happens as follows. Under the influence of an alternating magnetic flux , the electromotive force (EMF) of induction changes.
EMF acts so that eddy currents flow inside the bodies, which emit heat in full accordance with the Joule-Lenz law. EMF also generates alternating current in the metal. In this case, heat 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 achieve very high temperatures at which you can process the most refractory metals.
To ensure induction heating, it is required 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 - converters and generators.
The simplest device of a low-frequency inductor is a spiral (insulated conductor), which can be placed inside a metal pipe or wound on 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. The processing of metals at medium and high frequencies is more common.
Such devices are characterized in that the magnetic wave enters the surface where it attenuates. The body converts the energy of this wave into heat. To achieve maximum effect, both components should be close in shape.
Where are used
The use of induction heating in the modern world is widespread. Scope of use:
- melting of metals, their soldering in a non-contact way;
- obtaining new metal alloys;
- engineering;
- jewelry making;
- the manufacture of small parts that may be damaged by other methods;
- hardening of surfaces (and details can be of the most complex configuration);
- heat treatment (processing of parts for machines, hardened surfaces);
- medicine (disinfection of devices and instruments).
Induction heating: positive features
This method has many advantages:
- With it, you can quickly heat and melt any current-conducting material.
- It allows heating in any environment: in a vacuum, atmosphere, non-conductive fluid.
- Due to the fact that only conductive material is heated, the walls, weakly absorbing waves, remain cold.
- In specialized areas of metallurgy, the production of ultrapure alloys. This is an entertaining process, because the metals are mixed in suspension, 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, as well as in arc heating, then induction eliminates this, due to "pure" electromagnetic radiation.
- Small dimensions of the inductor device.
- The possibility of manufacturing an inductor of any shape, this will not lead to local heating, but will contribute to an even distribution of heat.
- Indispensable if you need to heat only a certain surface area.
- It is not difficult to configure such equipment to the desired mode and adjust it.
disadvantages
The system has such disadvantages:
- It is quite difficult to independently establish and adjust the type of heating (induction) and its equipment. It is better to contact specialists.
- The need to accurately match the inductor and the workpiece, otherwise the induction heating will be insufficient, its power can reach small values.
Induction heating
To equip individual heating, you can consider such an option as induction heating.
A transformer consisting of two types of windings: primary and secondary (which, in turn, is short-circuited), will be used as an aggregate.
How does it work
The principle of operation of a conventional inductor: vortex flows pass inside and direct the electric field to the second housing.
In order for water to pass through such a boiler, two nozzles are connected to it: for cold, what comes in, and at the outlet of warm water - a second nozzle. Due to pressure, water is constantly circulating, which eliminates the possibility of heating the inductor element. The presence of scale here is excluded, since constant vibrations occur in the inductor.
Such an element in maintenance will be inexpensive. The main plus is that the device works silently. You can install it in any room.
Making equipment yourself
Installation of induction heating will not be very difficult. Even those who have no experience, after careful study, will cope with the task. Before you begin, you need to stock up on the following necessary elements:
- Inverter. It can be used from a welding machine, it is inexpensive and will be of high frequency. You can make it yourself. But this is a time consuming task.
- Heater housing (a piece of plastic pipe is suitable for this, induction heating of the pipe in this case will be most effective).
- Material (a wire with a diameter of not more than seven millimeters will fit).
- Devices for connecting the inductor to the heating network.
- Mesh for holding the wire inside the inductor.
- The induction coil can be created from copper wire (it must be enameled).
- Pump (so that water is supplied 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 power (it must be at least 15 amperes, if necessary, then more can be done).
- The wire should be cut into pieces of not more than five centimeters. This is necessary for effective heating in a high-frequency field.
- The case must be no smaller in diameter than the prepared wire and have thick walls.
- To attach to the heating network, a special adapter is mounted on one side of the structure.
- A mesh must be placed at the bottom of the pipe to prevent wire from falling out.
- The latter is needed in such a quantity that it fills the entire inner space.
- The design closes, an 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 apparatus. The coil is connected to the prepared inverter.
- A water pump is installed.
- The temperature regulator is mounted.
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 tires leading to the inductor, which can be much more than the indices of the inductor itself.
About cooking surfaces
Another use in household appliances, in addition to the heating system, was found by this type of heating in stove hobs.
Such a surface has the appearance of a conventional transformer. Its coil is hidden under the surface of the panel, which can be glass or ceramic. Current flows through it. This is the first part of the coil. But the second is the dishes in which cooking will take place. Eddy currents are created at the bottom of the dishes. They heat the dishes first, and then the products in it.
Heat will be released only when dishes are placed on the surface of the panel.
If it is absent, no action occurs. The induction heating zone will correspond to the diameter of the dishes placed on it.
For such plates you need special dishes. Most ferromagnetic metals can interact with the induction field: aluminum, stainless and enameled steel, cast iron. Not suitable for such surfaces only: copper, ceramic, glass and dishes made of non-ferromagnetic metals.
Naturally, the induction cooker will turn on only when a suitable cookware is installed on it.
Modern stoves are equipped with an electronic control unit, which allows you to recognize empty and unusable dishes. The main advantages of
induction hobs are: safety, ease of cleaning, speed, efficiency, profitability. On the surface of the panel can never be burned.
So, we found out where this type of heating (induction) is used.