In induction furnaces and devices, heat in a heated device is released by currents arising in an alternating electromagnetic field inside the unit. They are called induction. As a result of their action, the temperature rises. Induction heating of metals is based on two main physical laws:
- Faraday-Maxwell;
- Joule-Lenz.
In metallic bodies, when they are placed in an alternating field, vortex electric fields begin to appear.
Induction heating device
Everything happens as follows. Under the influence of a variable magnetic flux, the electromotive force (EMF) of induction changes.
EMF acts in such a way that eddy currents flow inside the bodies, which release heat in full accordance with the Joule-Lenz law. Also, the EMF generates an 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 easiest, as it is non-contact. It allows reaching very high temperatures, at whichthe most refractory metals can be machined.
To provide 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 for this - converters and generators.
The simplest low frequency inductor device is a spiral (insulated conductor), which can be placed inside a metal pipe or wound around it. The passing currents heat the pipe, which, in turn, transfers heat to the environment.
The use of induction heating at low frequencies is quite rare. More common metal processing at medium and high frequency.
Such devices differ in that the magnetic wave hits the surface, where it is attenuated. The body converts the energy of this wave into heat. For maximum effect, both components should be close in shape.
Where used
The use of induction heating in the modern world is widespread. Area of use:
- melting of metals, their soldering in a contactless way;
- obtaining new metal alloys;
- mechanical engineering;
- jewellery;
- make small parts that can be damaged by other methods;
- surface hardening (moreover, parts can be of the most complex configuration);
- heat treatment (machining machine parts, hardened surfaces);
- medicine (disinfection of appliances and tools).
Induction heating: positive features
This method has many advantages:
- It can quickly heat and melt any conductive material.
- Allows heating in any medium: vacuum, atmosphere, non-conductive liquid.
- Due to the fact that only the conductive material is heated, the walls that weakly absorb waves remain cold.
- In specialized areas of metallurgy obtaining ultra-pure alloys. This is an entertaining process, because the metals are mixed in a suspended state, in a shell of protective gas.
- Compared with other types, induction does not pollute the environment. If in the case of gas burners pollution is present, as well as in arc heating, then induction eliminates this, due to "clean" electromagnetic radiation.
- Small dimensions of the device inductor.
- The ability to manufacture an inductor of any shape, this will not lead to local heating, but will contribute to a uniform distribution of heat.
- Irreplaceable if only a certain area of the surface needs to be heated.
- It is not difficult to set up such equipment for the desired mode and regulate it.
Flaws
The system has the following disadvantages:
- Self-install andadjusting the type of heating (induction) and its equipment is quite difficult. It is better to turn to specialists.
- The need to accurately match the inductor and the workpiece, otherwise the induction heating will be insufficient, its power may reach small values.
Induction heating equipment
For the arrangement of individual heating, you can consider an option such as induction heating.
The unit will be a transformer consisting of two types of windings: primary and secondary (which, in turn, is short-circuited).
How it works
The principle of operation 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 brought to it: for cold water, which enters, and at the outlet of warm water - the second pipe. Due to the pressure, the 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 item would be inexpensive to maintain. 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 do not have experience, after careful study, will cope with the task. Before starting work, you need to stock up on the following necessary items:
- Inverter. It can be usedfrom the welding machine, it is inexpensive and will need high frequency. You can make it yourself. But this is a time-consuming activity.
- Heater housing (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.
- Grid to hold the wire inside the inductor.
- An induction coil can be created from copper wire (it must be enameled).
- Pump (to supply water to the inductor).
Rules for making equipment yourself
In order for the induction heating unit to work correctly, the current for such a product must correspond to the power (it must be at least 15 amperes, if required, then more).
- The wire must 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 design is closed, an adapter is placed.
- Then a coil is constructed from this pipe. To do this, wrap it alreadyprepared 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 pump is being installed.
- The temperature controller 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 higher than the inductor itself.
About hobs
Another application in household use, in addition to the heating system, this type of heating found in stove hobs.
This surface looks like 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 food in it.
Heat will only be released when dishes are placed on the surface of the hob.
If it is missing, no action occurs. The induction cooking zone will match the diameter of the cookware placed on it.
For such stoves, special dishes are needed. Most ferromagneticmetals 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 only turn on when suitable cookware is placed 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, economy. The surface of the panel should never be burned.
So, we found out where this type of heating (induction) is used.
