A household induction stove can easily heat your home. In industry, these devices are used in smelting various metals. Additionally, they can participate in the heat treatment of parts, as well as their hardening. The main advantage of an induction oven is its ease of use. In addition, they are easy to maintain and do not require periodic inspections, which is very important.
There is absolutely no need to allocate a separate room to install this device. The performance of these devices is very good. This is largely due to the fact that the design does not contain parts that are subject to mechanical wear. In general, induction furnaces are safe for human health and do not pose any danger during operation.
How it works?
The operation of an induction furnace begins with the supply of alternating current to the generator. At the same time, it passes through a special inductor, which is located inside the structure. Next, the device uses a capacitor. Its main task is the formation of an oscillatory circuit. In this case, the entire system is tuned to the operating frequency. The inductor in the furnace creates an alternating magnetic field. At this time, the voltage in the device increases to 200 V.
To close the circuit, the system has a ferromagnetic core, but it is not installed in all models. Subsequently, the magnetic field interacts with the workpiece and creates a powerful flux. Next, the electrically conductive element is induced and a secondary voltage arises. In this case, an eddy current is formed in the capacitor. According to the Joule-Lenz law, it gives its energy to the inductor. As a result, the workpiece in the furnace heats up.
Homemade induction ovens
A do-it-yourself induction furnace is made strictly according to the drawings in compliance with safety rules. The device housing should be selected from aluminum alloy. A large platform should be provided at the top of the structure. Its thickness must be at least 10 mm. A steel template is most often used to fill the crucible. To drain the molten metal, you will need a lining cavity in the form of a spout. In this case, the structure must have a padding area.
For sections, an insulating stand is installed above the template. Directly below it will be a hinged support. In order to cool the inductor, the furnace must have a fitting. Voltage is supplied to the device through the bridge, which is located at the bottom of the device. To tilt the container, a self-made induction furnace must have a separate gearbox. In this case, it is best to make a handle so that you can drain the metal manually.
Furnaces of the Termolit company
Induction furnaces for melting metal of this type trademark have acceptable converter power. However, the capacity of the cameras in the models may vary greatly. The average metal melting rate is 0.4 t/h. In this case, the nominal voltage of the supply network fluctuates around 0.3 V. The water consumption in an induction furnace depends on the cooling system. Typically this parameter is 10 cubic meters/hour. Wherein specific consumption electricity is quite high.
Characteristics of the Termolit TM1 furnace
This melting furnace (induction) has a total capacity of 0.03 tons. At the same time, the converter power is only 50 kW, and the average melting speed is 0.04 tons per hour. The supply voltage must be at least 0.38 V. The water consumption for cooling in this model is insignificant. This is largely due to low power devices.
One of the disadvantages is the high energy consumption. On average, the furnace consumes approximately 650 kW per hour of operation. The frequency converter in this model is of the TFC-50 class. In general, Termolit TM1 is an economical equipment, but with poor performance.
Induction furnace "TG-2"
Induction melting furnaces of the "TG" series are produced with a chamber capacity of 0.6 tons. The rated power of the device is 100 kW. Moreover, in an hour of continuous operation it is possible to melt 0.16 tons of non-ferrous metals. This model is powered from a network with a voltage of 0.3 V.
The water consumption of the induction-type furnace "TG-2" is quite significant and on average up to 10 cubic meters of liquid are consumed per hour of operation. All this is due to the need for intensive cooling of the gearbox. On the positive side is moderate power consumption. Typically, up to 530 kW of electricity is consumed per hour of operation. The frequency converter in the TG-2 model is installed in the TFC-100 class.
Furnaces "Thermo Pro"
The main modifications of equipment from this company are induction melting furnaces "SAT 05", "SAK-1", and "SOT 05". Their average nominal melting point is 900 degrees. At the same time, the power of the devices fluctuates around 150 kW. Additionally, their good performance should be noted. In an hour of work, non-ferrous metals can be melted 80 kg. At the same time, many Thermo Pro models are manufactured for highly targeted use. Some are designed exclusively for working with aluminum, while others are designed to melt lead or tin.
Modification "SAT 05"
This induction furnace is designed to melt aluminum. The power of this device is exactly 20 kW. At the same time, up to 20 kg of metal can be passed through per hour of operation. The chamber capacity in the "SAT 05" model is 50 kg, and the frequency converter is of the "TFC" class.
The batteries in the device are of the capacitor type. The manufacturer installed a special water-cooled cable in the lower part of the structure. This model has a control panel. Among other things, it is worth noting the large set of SAT 05 stove. It includes all installation accessories, as well as operational documents.
Parameters of the SAK-1 furnace
This induction furnace is most often used for smelting lead as well as tin. In some cases, it is allowed to use copper, but productivity drops significantly. The average melting point fluctuates around 1000 degrees, power this device has 250 kW. In an hour of continuous operation, it is possible to pass up to 400 kg of non-ferrous metals. At the same time, the capacity of the equipment allows loading up to 1000 kg of material. The supply voltage is 0.3 kV.
The water consumption for cooling the SAK-1 model is insignificant. The oven consumes approximately 10 cubic meters of liquid per hour. The specific electricity consumption is also small and amounts to 530 kW. The frequency converter in this design is of the TPCH-400 brand. In general, the SAK-1 model turned out to be economical and easy to use.
Review of the model "SAK 05"
Induction furnaces for metal melting "SAK 05" are distinguished by a large capacity - 0.5 tons. At the same time, the power of the supply converter is 400 kW. The operating melting speed in this furnace is quite high. The rated voltage of the device is 0.3 kV. During an hour of operation, approximately 11 cubic meters of water are consumed to cool the system. It should also be noted that the electricity consumption is considerable and amounts to 530 kW. The frequency converter in the device is of the TFC-400 class. At the same time, it is capable of increasing the maximum temperature to 800 degrees. The induction furnace "SAK 05" is intended exclusively for melting aluminum and bronze. The heat exchange cabinet was installed by the manufacturer of the "IM" brand. Another thing worth noting is the convenient remote control. There is an alarm system and a hydraulic station in the system.
Among other things, the standard kit includes a set of turbo tires and mounting accessories. In general, the “SAK 05” model turned out to be quite protected, and you can use it without risk to health. This was largely achieved through rods that are mounted on hydraulic cylinders. In this case, the metal practically does not splash. Direct frequency adjustment during operation occurs in automatic mode. Capacitors are used in this medium voltage model.
The plate is the key element household appliances, which is impossible to do without in any kitchen.
And if earlier housewives’ assistants were electric and, now induction stoves are gaining popularity. And this is justified, because they have a lot of undeniable advantages: fire safety, efficiency, high speed of heating and cooking.
Induction ovens - the most modern household appliances for the kitchen
Working principle of induction furnace
The induction oven appeared on the household appliances market in the 80s of the last century, but the invention was treated with distrust due to the high cost and unclear operating principle. Only after restaurateurs began to use induction hob and felt its advantages, housewives who wanted to simplify and speed up cooking took advantage of their example.
The operating principle of induction cookers is based on the use of magnetic field energy. A glass-ceramic copper coil underneath, when passing through the turns of which electricity converted to induction. When a cookware with a magnetic bottom is placed on a burner, the current acts on the electrons of its ferromagnetic material, causing them to move. As a result of this process, heat is released, due to which the cookware heats up and the contents in it enter the cooking stage.
To cook on an induction hob you need special cookware
Induction is fundamentally different from electric and gas in the following aspects:
- Heating the coating. In traditional stoves, the burner heats up first and then transfers the heat to the cookware sitting on it. Induction heating involves heating the bottom of a frying pan or pan directly. Glass ceramic panel At the same time, it heats up from the dishes, and after removing them cools down for 5 minutes.
- Efficiency. Induction electric stoves have an efficiency of 90% due to the fact that energy is not wasted on heating the burner, but acts on the bottom of the pan.
- Energy saving. The temperature adjustment of the induction furnace occurs almost instantly, which leads to rational energy consumption.
- Safety. When the stove is operating, the panel itself does not heat up, so you don’t have to worry about getting burned.
Features of cooking
Housewives often deliberately refuse to purchase electric induction stoves because they are afraid of difficulties when turning on and cooking. In fact, there is nothing difficult about turning on an induction cooker.
After connecting the device to the power source, a signal will sound notifying you that the hob can be turned on. Each zone has a power regulator and a customizable timer.
Unusual design induction cooker
How to cook on an induction hob is described in detail in the instructions for its use. There are marked temperature conditions and power parameters required for a specific cooking process of a particular dish. For example, boiling water occurs at levels 7-9, extinguishing - 5 or 6.
Types of slabs
The household appliances market offers ovens of varying functionality and cost. Users can purchase both inexpensive induction cookers for the kitchen and multifunctional systems installed in cafes and restaurants.
The main types of this equipment include:
- compact tabletop induction cookers with one or more burners;
- built-in appliances or separate hobs;
- combined stoves - combine elements operating on the principle of magnetic induction and electric heating burners.
Combined induction-gas stove
When choosing a stove based on magnetic field energy, you should pay attention to the power capabilities and the number of modes. Intensive heating function allows you to cook food faster .
Infrared sensors control the maximum heating of the bottom of the pan and prevent food from burning: in my opinion, this function is necessary in the device.
It’s also worth thinking about the shape of the burner: it can be flat or recessed. The possibility of using dishes with different bottoms will depend on this. Multifunctional devices, such as induction cookers with an oven and a large number of burners, will allow you to cook several dishes at the same time.
Specifications
Depending on the type and cost, electric induction furnaces have the following technical characteristics:
- maximum heating temperature is 60 degrees Celsius;
- power ranges from 50-3500 W;
- the number of adjustment modes varies from 12 to 20 depending on the type of device;
- devices are equipped with a touch panel;
- the heating element operates on the basis of induction;
- The device is equipped with a timer.
Like any equipment, this one is not immune to breakdowns, but finding spare parts for induction cookers is not difficult. In addition, people who understand the laws of physics can easily make an induction cooker with their own hands. However, remember that you should take on this business only if you have the necessary knowledge and experience.
Selecting cookware for an induction cooker
Many housewives are sure that they will have to buy all the cookware for the induction cooker again, since the existing one will not fit. This is not entirely true.
To put an induction hob into operation, you must use cookware that has ferromagnetic properties. Checking this is quite simple: you need to attach a magnet to the bottom. If it sticks, the pan is suitable for use on the stovetop.
Iron, enameled and cast iron pans have ferromagnetic properties. Glass, ceramic, porcelain and copper containers are not suitable for ovens that use magnetic field energy.
If there are no suitable pots and pans available, choosing cookware for induction cookers will not be difficult if you use a few tips:
- bottom induction cookware must have a diameter of at least 12 cm to ensure optimal area contact with the surface of the stove;
- the thickness of the bottom of a grill pan for an induction cooker or other container must be at least 2 and no more than 6 mm;
- the bottom surface should be smooth, without bends;
- The symbol on the cookware for induction cookers, which looks like a horizontal spiral and indicates the use of ferromagnetic material, can help in choosing the right container.
There are many companies producing pots, frying pans, stewpans, fryers and even Turks for induction cookers. Therefore, buying them will not be difficult.
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If it is not possible to purchase a full set of special cookware, you can use an adapter for an induction cooker. It is a disk 2-3 mm thick with different diameters depending on the size of the pots and pans. The principle of operation is as follows: the coil transfers heat to the adapter for the induction cooker, which, in turn, heats the cookware standing on it. When using such a device, it is not necessary to buy a special kettle for an induction cooker; you can easily use your favorite ceramic one.
Ancient potters firing ceramic products in forges, sometimes shiny hard pieces with unusual properties were found at their bottom. From the very moment when they began to think about what these wonderful substances were, how they appeared there, and also where they could be used usefully, metallurgy was born - the craft and art of metal processing.
And the main tool for extracting new ore from ore is extremely useful materials steel thermomelting forges. Their designs have come a long way in development: from primitive disposable clay domes heated with wood to modern electric furnaces with automatic control of the melting process.
Metal-smelting units are needed not only by the giants of the ferrous metallurgy industry, which use cupola furnaces, blast furnaces, open-hearth furnaces and regenerative converters with a production of several hundred tons per cycle.
Such values are typical for the smelting of iron and steel, which account for up to 90% of the industrial production of all metals.
In non-ferrous metallurgy and recycling, the volumes are much smaller. And the global turnover of production of rare earth metals is generally calculated at several kilograms per year.
But the need for melting metal products arises not only when mass production. A significant sector of the metalworking market is occupied by foundry production, which requires metal-smelting units of relatively small output - from several tons to tens of kilograms. And for piece craft, arts and crafts production and jewelry making, melting machines with a production capacity of several kilograms are used.
All types of metal smelting devices can be divided according to the type of energy source for them:
- Thermal. The coolant is flue gas or highly heated air.
- Electrical. Various thermal effects of electric current are used:
- Muffle. Heating of materials placed in a thermally insulated housing with a spiral heating element.
- Resistance. Heating a sample by passing a large current through it.
- Arc. Use high temperature electric arc.
- Induction. Melting of metal raw materials by internal heat from the action of eddy currents.
- Streaming. Exotic plasma and electron beam devices.
Flow electron beam melting furnace Thermal open hearth furnace Electric arc furnace
For small production volumes, the most expedient and economical is the use of electric ones, especially induction melting furnaces(IPP).
Construction of induction electric furnaces
In short, their action is based on the phenomenon of Foucault currents - eddy induction currents in a conductor. In most cases, electrical engineers deal with them as a harmful phenomenon.
For example, it is because of them that transformer cores are made of steel plates or tape: in a solid piece of metal, these currents can reach significant values, leading to useless energy losses for heating it. 
In an induction melting electric furnace, this phenomenon is used to advantage. In essence, it is a kind of transformer in which the role of a short-circuited secondary winding, and in some cases the core, is played by a molten metal sample. It is metallic - only materials that conduct electricity can be heated in it, while dielectrics will remain cold. The role of the inductor - the primary winding of the transformer is performed by several turns of a thick coil rolled up into a coil. copper tube, through which coolant circulates.
By the way, the kitchen appliances that have become extremely popular operate on the same principle. hobs with induction high frequency heating. A piece of ice placed on them will not even melt, but placed metal utensils will heat up almost instantly.
Design features of induction thermal furnaces
There are two main types of PPIs:
For both types of metal-smelting units there are no fundamental differences in the type of working raw materials: they successfully melt both ferrous and non-ferrous metals. It is only necessary to select the appropriate operating mode and crucible type.
Selection options
Thus, the main criteria for choosing one or another type of thermal furnace are volumes and continuity of production. For a small foundry, for example, in most cases, a crucible electric furnace is suitable, and a channel furnace is suitable for a recycling plant.
In addition, one of the main parameters of a crucible hot furnace is the volume of one melt, based on which a specific model should be selected. Important characteristics are also the maximum operating power and the type of current: single-phase or three-phase.
Choosing a location for installation
The location of the induction furnace in a workshop or workshop should provide free access to it for the safe execution of all technological operations during the melting process:
- loading of raw materials;
- manipulations during the working cycle;
- unloading the finished melt.
The installation site must be provided with the necessary electrical networks with the required operating voltage and number of phases, protective grounding with the possibility of quick emergency shutdown of the unit. The installation must also be provided with a water supply for cooling.
Tabletop structures of small dimensions must nevertheless be installed on strong and reliable individual bases not intended for other operations. Floor-standing units also need to be provided with a solid, reinforced foundation.
It is prohibited to place fire and explosive materials in the melt unloading area. A fire shield with extinguishing agents must be hung near the location of the stove.
Installation instructions
Industrial thermomelting units are devices with high energy consumption. Their installation and electrical installation must be carried out by qualified specialists. Small units with a load of up to 150 kg can be connected by a qualified electrician, following normal electrical installation rules.
For example, an IPP-35 furnace with a power of 35 kW with a production volume of 12 kg of ferrous metals and up to 40 non-ferrous metals has a mass of 140 kg. Accordingly, its installation will consist of the following steps:
- Selecting a suitable location with a solid base for the thermomelting unit and high-voltage water-cooled induction unit with capacitor bank. The location of the unit must comply with all operational requirements and electrical and fire safety regulations.
- Providing the installation with a water cooling line. The described electric melting furnace is not supplied with cooling equipment, which must be purchased additionally. The best solution it will have a double-circuit closed-cycle cooling tower.
- Connection of protective grounding.
The operation of any electric melting furnaces without grounding is strictly prohibited.
- Supplying a separate electrical line with a cable whose cross-section provides the appropriate load. The power shield must also provide the required load with a power reserve
For small workshops and home use mini-furnaces are produced, for example, UPI-60-2, with a power of 2 kW with a crucible volume of 60 cm³ for melting non-ferrous metals: copper, brass, bronze ~ 0.6 kg, silver ~ 0.9 kg, gold ~ 1.2 kg . The weight of the installation itself is 11 kg, dimensions are 40x25x25 cm. Its installation consists of placing it on metal workbench, connecting flow water cooling and plugging it into a power outlet.
Technology of use
Before starting work with a crucible electric furnace, you should definitely check the condition of the crucibles and lining - the internal protective thermal insulation. If it is designed to use two types of crucibles: ceramic and graphite, you must select the appropriate material for the loaded material according to the instructions.
Typically, ceramic crucibles are used for ferrous metals, graphite crucibles for non-ferrous ones.
Operating procedure:
- Insert the crucible inside the inductor and, after loading it with the working material, cover it with a heat-insulating lid.
- Turn on water cooling. Many models of electric melting units will not start if not required pressure water.
- The melting process in a crucible IPP begins with its switching on and entering the operating mode. If there is a power regulator, set it to the minimum position before turning it on.
- Smoothly increase the power to operating power corresponding to the loaded material.
- After melting the metal, reduce the power to a quarter of the working power to maintain the material in a molten state.
- Before spilling, turn the regulator down to minimum.
- Upon completion of melting, turn off the power to the installation. Turn off water cooling after it has cooled down.
The unit must be under supervision throughout the melting process. Any manipulations with crucibles must be done using tongs and wearing protective gloves. In the event of a fire, the installation should be immediately de-energized and the flames should be knocked out with a tarpaulin or extinguished with any fire extinguisher other than acid. Filling with water is strictly prohibited.
Advantages of induction furnaces
- High purity of the resulting melt. In other types of metal-smelting thermal furnaces, there is usually direct contact of the coolant with the material, and, as a result, contamination of the latter. In IPP, heating is produced by the absorption of the electromagnetic field of the inductor by the internal structure of the conductive materials. Therefore, such furnaces are ideal for jewelry production.
For thermal furnaces, the main problem is reducing the content of phosphorus and sulfur in ferrous metal melts, which deteriorate their quality.
- High efficiency of induction melting devices, reaching up to 98%.
- High melting speed due to heating of the sample from the inside and, as a consequence, high performance IPP, especially for small working volumes up to 200 kg.
Warming up muffle electric furnace with a load of 5 kg occurs within several hours, IPP - no more than an hour.
- Devices with a loading capacity of up to 200 kg are easy to place, install and operate.
The main disadvantage of electric melting devices, and induction ones are no exception, is the relative high cost of electricity as a coolant. But despite this, the high efficiency and good performance of IPPs largely pay for them during operation.
The video shows an induction oven in operation.
Metal smelting by induction is widely used in various industries: metallurgy, mechanical engineering, jewelry. You can assemble a simple induction furnace for melting metal at home with your own hands.
Heating and melting of metals in induction furnaces occur due to internal heating and changes crystal lattice metal when high-frequency eddy currents pass through them. This process is based on the phenomenon of resonance, in which eddy currents have a maximum value.
To cause the flow of eddy currents through the molten metal, it is placed in the zone of action of the electromagnetic field of the inductor - the coil. It can be in the shape of a spiral, figure eight or trefoil. The shape of the inductor depends on the size and shape of the heated workpiece.
The inductor coil is connected to the source alternating current. In industrial melting furnaces, industrial frequency currents of 50 Hz are used; for melting small volumes of metals in jewelry, high-frequency generators are used as they are more efficient.
Kinds
Eddy currents are closed along a circuit limited by the magnetic field of the inductor. Therefore, heating of the conductive elements is possible both inside the coil and on its outside.
- Therefore, induction furnaces come in two types:
- channel, in which the container for melting metals is channels located around the inductor, and a core is located inside it;
- crucible, they use a special container - a crucible made of heat-resistant material, usually removable.
Channel furnace too large and designed for industrial volumes of metal smelting. It is used in the smelting of cast iron, aluminum and other non-ferrous metals.
Crucible furnace It is quite compact, it is used by jewelers and radio amateurs; such a stove can be assembled with your own hands and used at home.
Device
- A homemade furnace for melting metals has a fairly simple design and consists of three main blocks placed in a common body:
- high frequency alternating current generator;
- inductor - a spiral winding made of copper wire or tube, made by hand;
- crucible.
The crucible is placed in an inductor, the ends of the winding are connected to a current source. When current flows through the winding, an electromagnetic field with a variable vector appears around it. In a magnetic field, eddy currents arise, directed perpendicular to its vector and passing along closed loop inside the winding. They pass through the metal placed in the crucible, heating it to the melting point.
Advantages of an induction furnace:
- fast and uniform heating of the metal immediately after turning on the installation;
- direction of heating - only the metal is heated, and not the entire installation;
- high melting speed and melt homogeneity;
- there is no evaporation of metal alloying components;
- The installation is environmentally friendly and safe.
A welding inverter can be used as a generator for an induction furnace for melting metal. You can also assemble a generator using the diagrams below with your own hands.
Furnace for melting metal using a welding inverter
This design is simple and safe, since all inverters are equipped with internal overload protection. The entire assembly of the furnace in this case comes down to making an inductor with your own hands.
It is usually performed in the form of a spiral from a thin-walled copper tube with a diameter of 8-10 mm. It is bent according to a template required diameter, placing the turns at a distance of 5-8 mm. The number of turns is from 7 to 12, depending on the diameter and characteristics of the inverter. The total resistance of the inductor must be such as not to cause overcurrent in the inverter, otherwise it will be turned off by the internal protection.
The inductor can be fixed in a housing made of graphite or textolite and a crucible can be installed inside. You can simply place the inductor on a heat-resistant surface. The housing must not conduct current, otherwise eddy currents will pass through it and the power of the installation will decrease. For the same reason, it is not recommended to place foreign objects in the melting zone.
When working from welding inverter its body must be grounded! The outlet and wiring must be rated for the current drawn by the inverter. 
The heating system of a private home is based on the operation of a stove or boiler, the high performance and long uninterrupted service life of which depends on both the brand and installation itself heating devices, and from correct installation chimney.
You will find recommendations for choosing a solid fuel boiler, and in the next section you will get acquainted with the types and rules:
Induction furnace with transistors: diagram
There are many different ways to collect induction heater with your own hands. A fairly simple and proven diagram of a furnace for melting metal is shown in the figure:
- To assemble the installation yourself, you will need the following parts and materials:
- two field-effect transistors type IRFZ44V;
- two UF4007 diodes (UF4001 can also be used);
- resistor 470 Ohm, 1 W (you can take two 0.5 W connected in series);
- film capacitors for 250 V: 3 pieces with a capacity of 1 μF; 4 pieces - 220 nF; 1 piece - 470 nF; 1 piece - 330 nF;
- copper winding wire in enamel insulation Ø1.2 mm;
- copper winding wire in enamel insulation Ø2 mm;
- two rings from inductors removed from the computer power supply.
DIY assembly sequence:
- Field effect transistors are installed on radiators. Since the circuit gets very hot during operation, the radiator must be large enough. You can install them on one radiator, but then you need to isolate the transistors from the metal using gaskets and washers made of rubber and plastic. The pinout of field-effect transistors is shown in the figure.
- It is necessary to make two chokes. To make them, copper wire with a diameter of 1.2 mm is wound around rings removed from the power supply of any computer. These rings are made of powdered ferromagnetic iron. It is necessary to wind from 7 to 15 turns of wire on them, trying to maintain the distance between the turns.
- The capacitors listed above are assembled into a battery with a total capacity of 4.7 μF. The connection of capacitors is parallel.
- The inductor winding is made of copper wire with a diameter of 2 mm. Wrap 7-8 turns of winding around a cylindrical object suitable for the diameter of the crucible, leaving the ends long enough to connect to the circuit.
- Connect the elements on the board in accordance with the diagram. A 12 V, 7.2 A/h battery is used as a power source. The current consumption in operating mode is about 10 A, the battery capacity in this case will last for about 40 minutes. If necessary, the furnace body is made from a heat-resistant material, for example, textolite. The power of the device can be changed by changing the number of turns of the inductor winding and their diameter.
Induction heater for metal melting: video
Induction furnace with lamps
You can assemble a more powerful induction furnace for melting metals with your own hands using electronic tubes. The device diagram is shown in the figure. 
To generate high-frequency current, 4 beam lamps connected in parallel are used. A copper tube with a diameter of 10 mm is used as an inductor. The installation is equipped with a tuning capacitor to regulate power. The output frequency is 27.12 MHz.
To assemble the circuit you need:
- 4 electron tubes - tetrodes, you can use 6L6, 6P3 or G807;
- 4 chokes at 100...1000 µH;
- 4 capacitors at 0.01 µF;
- neon indicator lamp;
- trimmer capacitor.
Assembling the device yourself:
- An inductor is made from a copper tube by bending it into a spiral shape. The diameter of the turns is 8-15 cm, the distance between the turns is at least 5 mm. The ends are tinned for soldering to the circuit. The diameter of the inductor should be 10 mm larger than the diameter of the crucible placed inside.
- The inductor is placed in the housing. It can be made from a heat-resistant, non-conducting material, or from metal, providing thermal and electrical insulation from the circuit elements.
- Cascades of lamps are assembled according to a circuit with capacitors and chokes. The cascades are connected in parallel.
- Connect a neon indicator lamp - it will signal that the circuit is ready for operation. The lamp is brought out to the installation body.
- The circuit includes a tuning capacitor variable capacity, its handle is also brought out onto the body.
For all lovers of delicacies prepared using the cold smoking method, we suggest you learn how to quickly and easily make a smokehouse with your own hands, and get acquainted with the photo and video instructions for making a smoke generator for cold smoking.
Circuit cooling
Industrial smelting plants are equipped with a forced cooling system using water or antifreeze. Carrying out water cooling at home will require additional costs comparable in price to the cost of the metal melting installation itself.
Execute air cooling using a fan is possible, provided the fan is located sufficiently remotely. Otherwise, the metal winding and other elements of the fan will serve as an additional circuit for closing eddy currents, which will reduce the efficiency of the installation.
Elements of electronic and lamp circuits can also actively heat up. To cool them, heat sinks are provided.Safety precautions when working
- The main danger during work is the risk of burns from heated elements of the installation and molten metal.
- The lamp circuit includes high-voltage elements, so it must be placed in a closed housing to prevent accidental contact with the elements.
- The electromagnetic field can affect objects located outside the device body. Therefore, before work, it is better to put on clothes without metal elements, remove complex devices from the coverage area: phones, digital cameras.
A furnace for melting metals at home can also be used to quickly heat metal elements, for example, when tinning or forming them. The operating 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 generating sets - this way you can achieve their maximum efficiency.
Induction melting is a widely used process in ferrous and non-ferrous metallurgy. Induction smelting is often superior to fuel-fired smelting in terms of energy efficiency, product quality and production flexibility. These pre-
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properties are determined by the specific physical characteristics of induction furnaces.
During induction melting, a solid material is converted into a liquid phase under the influence of an electromagnetic field. As in the case of induction heating, heat is released in the melted material due to the Joule effect from induced eddy currents. The primary current passing through the inductor creates an electromagnetic field. Regardless of whether the electromagnetic field is concentrated by magnetic cores or not, the coupled inductor-load system can be represented as a transformer with a magnetic core or as an air transformer. The electrical efficiency of the system is highly dependent on the field-influencing characteristics of the ferromagnetic components.
Along with electromagnetic and thermal phenomena, electrodynamic forces play an important role in the induction melting process. These forces must be taken into account, especially in the case of melting in powerful induction furnaces. The interaction of induced electric currents in the melt with the resulting magnetic field causes a mechanical force (Lorentz force)
Pressure Melt flows
Rice. 7.21. Action of electromagnetic forces
For example, the turbulent movement of the melt caused by forces has a very great importance both for good heat transfer and for mixing and adhesion of non-conducting particles in the melt.
There are two main types of induction furnaces: induction crucible furnaces (IFC) and induction channel furnaces (ICF). In ITP, the molten material is usually loaded in pieces into a crucible (Fig. 7.22). The inductor covers the crucible and the melted material. Due to the absence of a concentrating field of the magnetic circuit, the electromagnetic connection between
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inductor and loading strongly depends on the wall thickness of the ceramic crucible. To ensure high electrical efficiency, the insulation must be as thin as possible. On the other hand, the lining must be thick enough to withstand thermal stresses and
metal movement. Therefore, a compromise should be sought between electrical and strength criteria.
Important characteristics of induction melting in ITP are the movement of the melt and the meniscus as a result of the influence of electromagnetic forces. The movement of the melt ensures both uniform temperature distribution and homogeneous chemical composition. The mixing effect at the surface of the melt reduces material losses during additional loading of small-sized charge and additives. Despite the use of cheap material, the reproduction of a melt of constant composition ensures high quality casting
Depending on the size, type of material being melted and the field of application, ITPs operate at industrial frequency (50 Hz) or medium frequency.
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at frequencies up to 1000 Hz. The latter are becoming increasingly important thanks to high efficiency when melting cast iron and aluminum. Since the melt motion at constant power is weakened with increasing frequency, higher power densities and consequently greater productivity become available at higher frequencies. Due to the higher power, the melting time is reduced, which leads to increasing efficiency process (compared to furnaces operating at industrial frequency). Taking into account other technological advantages, such as flexibility in changing melted materials, mid-frequency ITPs are designed as the high-power melting plants that currently dominate the iron foundry industry. Modern powerful mid-frequency ITS for cast iron melting have a capacity of up to 12 tons and a power of up to 10 MW. Industrial-frequency ITPs are developed for larger capacities than medium-frequency ones, up to 150 tons for cast iron melting. Intensive mixing of the bath is of particular importance when smelting homogeneous alloys, such as brass, therefore, industrial frequency ITPs are widely used in this area. Along with the use of crucible furnaces for smelting, they are currently also used for holding liquid metal before casting.
In accordance with the energy balance of IHP (Fig. 7.23), the level of electrical efficiency for almost all types of furnaces is about 0.8. Approximately 20% of the initial energy is lost in the inductor in the form of Joe heat. The ratio of heat losses through the crucible walls to the electrical energy induced in the melt reaches 10%, so the total efficiency of the furnace is about 0.7.
The second widely used type of induction furnace is the IKP. They are used for casting, aging and, especially, melting in ferrous and non-ferrous metallurgy. The ICP generally consists of a ceramic bath and one or more induction units (Fig. 7.24). IN
In principle, the induction unit can be represented as a transform
The operating principle of the IKP requires the presence of a constantly closed secondary loop, so these furnaces operate with a liquid residue of the melt. Useful heat is generated mainly in the channel, which has a small cross-section. The circulation of the melt under the influence of electromagnetic and thermal forces ensures sufficient heat transfer into the bulk of the melt located in the bath. Until now, ICPs have been designed for industrial frequency, however research papers are also carried out for higher frequencies. Thanks to the furnace's compact design and very good electromagnetic coupling, its electrical efficiency reaches 95%, and its overall efficiency reaches 80% and even 90%, depending on the material being melted.
According to the technological conditions in different fields of application, ICPs are required various designs induction channels. Single-channel furnaces are mainly used for aging and casting,
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steel melting is less common at installed capacities of up to 3 MW. For melting and holding non-ferrous metals, two-channel designs are preferable, providing best use energy. In aluminum melting plants, the channels are made straight for ease of cleaning.
The production of aluminum, copper, brass and their alloys is the main area of application of IKP. Today, the most powerful ICPs with a capacity
up to 70 tons and a power of up to 3 MW are used for aluminum smelting. Along with high electrical efficiency, low melt losses are very important in aluminum production, which predetermines the choice of ICP.
Promising applications of induction melting technology include the production of high-purity metals such as titanium and its alloys in cold crucible induction furnaces and the melting of ceramics such as zirconium silicate and zirconium oxide.
When melting in induction furnaces, the advantages of induction heating are clearly manifested, such as high density energy and productivity, melt homogenization due to stirring, precise
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energy and temperature control, as well as ease of automatic process control, ease manual control and greater flexibility. High electrical and thermal efficiencies combined with low melt losses and, therefore, savings in raw materials result in low specific energy consumption and environmental competitiveness.
The superiority of induction melting devices over fuel ones is constantly increasing due to practical research, supported by numerical methods for solving electromagnetic and hydrodynamic problems. As an example, we can note the internal coating of the IKP steel casing with copper strips for copper smelting. Reducing eddy current losses increased the efficiency of the furnace by 8%, and it reached 92%.
Further improvement of the economic performance of induction melting is possible through the use of modern technologies controls such as tandem or dual power control. Two tandem ITPs have one power source, and while melting is underway in one, the molten metal is held in the other for casting. Switching the power source from one furnace to another increases its utilization. A further development of this principle is dual power control (Fig. 7.25), which ensures long-term simultaneous operation of furnaces without switching using special automatic process control. It should also be noted that an integral part of the economics of smelting is the compensation of total reactive power.
In conclusion, to demonstrate the advantages of energy- and material-saving induction technology, we can compare fuel and electrothermal methods for melting aluminum. Rice. 7.26 shows a significant reduction in energy consumption per ton of aluminum when melting in
Chapter 7. Energy-saving capabilities of modern electrical technologies
□ metal loss; Shch melting
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induction channel furnace with a capacity of 50 tons. The final energy consumption is reduced by approximately 60%, and the primary energy by 20%. At the same time, CO2 emissions are significantly reduced. (All calculations are based on typical German energy conversion and CO2 emission coefficients for mixed power plants). The results obtained highlight the special influence of metal losses during melting associated with its oxidation. Their compensation requires a large additional expenditure of energy. It is noteworthy that in copper production, metal losses during smelting are also large and must be taken into account when choosing a particular smelting technology.
