An inductive heater works by the interaction of eddy currents generated by the electromagnetic field of the inductor with a metal surface. There are several schemes for making an induction heater with your own hands. The most affordable of them are structures made of polypropylene pipes and a welding inverter.
The principle of operation of the induction heater
When an alternating electric current flows along the coil of the inductor, an electromagnetic field is formed around it. When a metal core with magnetic properties is placed in the middle of the coil, its temperature rises. This induction heating is a phenomenon caused by eddy currents. It is observed only when the choke is supplied with an alternating electric current, which has a sufficient frequency of changes in sign and direction. When a DC current is applied to an inductive part, there is no change in core temperature.
The operation of the inductor for heating the workpieces is based on this principle. The main component of the unit in most cases is a spiral configuration made of metal. In cooking hobs, this role is played by a flattened element located at a short distance from the hob. In a heating boiler, the role of an inductor is played by a steel tube filled with a coolant (its function is performed by a liquid).
The important components of the unit under consideration are the alternator and the heating element. The first is used to obtain power supply of a sufficiently high frequency from a typical residential electrical network of 50 Hz. The second is a metal structure capable of absorbing heat while in field space. The generator sends an electric current adjusted to the required parameters to the inductor (spiral element). In this case, a stream of charged particles passes through the coil, creating a field. The metal placed in the zone of its action is heated by the action of Fouquet currents without direct contact with the inductor. To heat water in such a unit, it must be in contact with the heating element. The simplest example of such a design would be a metal pipe through which a stream of water passes. In the process, the liquid cools the walls, which prolongs the life of the structure.
Advantages and disadvantages of the device
Induction heating can provide a number of benefits that the use of electrode attachments cannot provide. Since the heating of the liquid is carried out by a metal element that does not take part in electrochemical reactions, the durability of the device depends only on the coil. The duration of its operation is determined by the duration of the operation of the device. Some inductors remain operational for more than 10 years. This is also related to the compatibility of the unit with different types of heat transfer fluids. In addition to plain water, machine oils and anti-freeze compositions are suitable for this role.
The internal parts of the unit are not covered with limescale accumulations during use.Due to constant contact with liquid, the possibility of overheating of parts is reduced, which also contributes to an extension of the service life. Convection in the device usually reaches a sufficient level that it is not necessary to install a circulation pump. There is no need for soundproofing measures - the device works quite quietly.
However, the induction heater also has weaknesses:
- The device requires electrical energy to function. In a room where there is no electricity or there is no way to provide access to it, the boiler will not be able to work. In places with regular network interruptions, it will not work efficiently.
- When the temperature rises too much, the heat-transferring liquid turns into a gaseous state. This provokes a strong increase in pressure in the structure, as a result of which pipe rupture can occur. To prevent this from happening, it will be necessary to equip the installation with pressure and temperature control devices. It can be a pressure gauge, a temperature sensor, an emergency shutdown device when the parameters are outside the specified range.
The need for additional tooling can contribute to a significant increase in equipment costs for a homemade induction heater.
The device is considered to be almost completely silent, but in practice this is not always the case. This applies to industrial models and installations designed at home.
Homemade device options
There are several ways to make a heater at home. The most affordable option is to make a device from a kitchen electric stove and a polypropylene pipe. The inverter device is difficult to execute, but powerful enough.
Pipe heating element
This development involves dismantling a spiral inductor installed in an electric stove and placing a new design in its place. For its manufacture, you will need a polypropylene tube 0.5 m long and 4 cm in diameter, a magnetic element, 5 textolite rods, taps for connection to the heating network. You will also need to purchase a coil of conductor with a cross-section of 2 mm² coated with glass insulation (such a cable is often used in welding transformer devices) and metal scouring pads for washing dishes.
The sequence of actions in the manufacture of the device:
- A magnet is placed in the tube and filled with washcloths (instead of them, chopped wire is acceptable).
- The bends are fitted with threads.
- Rods are glued along the body, on which a wire covered with glass insulation is wound.
- The hob is disassembled and the factory inductor, made in the form of a flat spiral, is removed from it. A prepared structure is installed in its place.
The heater in this apparatus is a metal washcloth placed in the alternating field of the coil. When starting the panel in maximum mode with parallel passing of water, it will turn out to be heated by 15-20 ° C. Considering that the tiles used for the construction usually have a power of no more than 2000 W, the resulting unit is suitable for heating residential premises with an area of up to 25 m².
The efficiency of the device can be increased by connecting it to a welding machine, but this work is fraught with a number of difficulties. Firstly, the device will need to be disassembled and looked for places on the diagram that have not yet been rectified. This is due to the fact that a direct current is created in it, and an alternating current is required for the heater to function. Secondly, you will need to use thicker wiring (for example, copper with a diameter of 1.5 mm, covered with an enamel compound) and calculate the required number of turns.Finally, a cooling mechanism will need to be incorporated into the installation.
Assembling an induction boiler
This solution does not involve disassembling the tiles. Instead, the master will need to weld the boiler tank according to its dimensions. A profile tube made of steel with a thickness of 2 mm and a hole size of 2 by 4 cm is taken. It will be necessary to make blank elements from it along the width of the panel. Pipes are welded lengthwise, matching the smaller sides. Up and down to the end parts, you need to hermetically weld iron tires. Holes are made in them and threaded pipes are installed. You also need to weld a couple of corners that form a shelf for the oven.
The apparatus should be painted with a temperature-resistant enamel composition. After it has dried and fixed, the boiler is mounted on the wall and embedded in the heating system. The hob fits into a nest with corners and is connected to the electrical network. Then you need to fill the installation with a coolant, bleed air masses and start heating the inductor element.
A homemade heater is not powerful enough to heat large living spaces. In a frosty winter, he will be able to heat two small rooms. During the transitional seasons, when the outside air temperature is around zero, the unit will be able to serve large areas - up to 40 m2.
From a welding inverter
When intending to use the welding machine, it must be borne in mind that it is strictly forbidden to connect the inductor to its terminals directly. Violation of this requirement is fraught with the loss of performance of all elements of the installation. To combine an inductive heater with a welding machine, the latter will have to carry out a number of complex manipulations that require the experience of the master and a detailed understanding of the unit's device. The primary winding must be connected after the converter of high-frequency signals of the inverter mechanism instead of its built-in inductive choke. In addition, it is necessary to solder the condensation unit and dismantle the diode bridge.
How to make a powerful induction heater
The considered devices have a power consumption in the region of 2.5 kW. To make a device with a higher rate (4 kW), a master needs serious knowledge in the field of radio electronics. It is not safe for an inexperienced radio amateur to take on this work.
One of the options may be a construction of a power supply unit with two pairs of windings, a transformer, driver and control boards. The value of the frequency at which the unit operates is inferior to the resonant one. Two coils are used to supply the drivers, one is for the control board, and the other is the power one. It powers the relay starter, fan and chiller pump.
Safety Tips
Plants of this type are widely used not only for space heating, but also for carrying out smelting works. The main problem with home-made induction devices is the lack of components that provide temperature and pressure control and explosion protection. Therefore, when operating such units, care and caution must be exercised.
Before starting the boiler, it is necessary to check the filling of the cavity with the coolant. The case, made of polymers, will begin to melt without regular cooling with liquid. This entails deformation changes and complete failure of the installation. Also, the danger can be represented by the fallout of the heated metal from the melting body. In such an incident, it will be necessary to replace a number of unit assemblies.
The device is connected to electricity through a separate wire that runs from the shield. The contacts must be covered with insulating material.If a welding machine is involved in the structure, its inverter must be grounded. The wire used for this operation should be 4-6 mm across. To prevent excessive heating of the installation in the absence of water, it is advisable to install an overpressure valve in the inlet.
Conclusions and recommendations
There is a reason to take on the independent manufacture of the device if the household already has an induction panel. The cost of purchasing it is quite high and comparable to the price of an electrode heater. The power of some of these models reaches 10 kW, while making an installation with an indicator above 2.5 kW at home can only be done by a master with the proper level of competence (at least, you need to be able to assemble a frequency converter circuit). Also, before installation, it is necessary to make sure that there are no cracks and holes through which liquid from the heat generator can leak out: such an incident can cause a fire.
An induction heater of a simple design, designed to serve a small area of \ u200b \ u200bthe room, is easy to make without special training. More powerful and efficient options, for example with a welding machine or two boards, require the assembler to be competent in the field of electronics. The structural features of these installations necessitate the purchase of additional controls to ensure safety.
