What phenomenon is the action of a microwave oven based on? Microwave oven

Vishnyakov Vasily Nikolaevich 1360

The microwave oven has long taken its place in the kitchen of an apartment or private house, in the break room of a modern office and behind the bar of small cafes. Ease of use creates a deceptive impression of simplicity of design, and few people think about the operating principles of such a familiar household appliance.

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A little physics

From time immemorial, the ether has been permeated by dozens of types of electromagnetic radiation. The light of the sun and stars, the warmth coming from the fire and the mysterious ultraviolet light that gives the skin a bronze or chocolate tint are just different manifestations of the same physical process.

Different wavelengths have different effects on human senses; the existence of many can be guessed only by indirect signs. Visible light (wavelength from 380 to 780 nm) causes chemical reactions in the cells of the retina, forming a picture of the world around us. The warming heat of a fire (from 2.5 to 2000 microns) is invisible to the eye, but is absorbed by the surface of the skin, giving a feeling of comfort and peace.

Waves in the decimeter range, with wavelengths from 10 to 100 cm and frequencies from 300 MHz to 3 GHz, are best absorbed by polar water molecules. Once in the zone of action of the electromagnetic field, H2O molecules are arranged in ordered structures located along the lines of force. Since the field is variable, the molecules are constantly rearranging, colliding with each other and transmitting their vibrations to their “neighbors.” And what does warm-up have to do with it? And despite the fact that the temperature of any body, homogeneous or not, is directly proportional to the kinetic energy of its atoms and molecules. The more intense the oscillatory movements, the higher the temperature. This process of converting the energy of electromagnetic vibrations into thermal energy of a physical body is called “dipole shift”.

And since the most water - up to 98% of the mass - contains animal and plant organics, decimeter waves are most suitable for heating, and therefore cooking.

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How does a microwave work?

The heart of the entire structure is the decimeter wave emitter or magnetron. Essentially, it is a powerful vacuum tube supplemented with an external magnetic field source. Electrons, moving from the cathode to the anode, are deflected under the influence of a constant external magnetic field, moving along an increasingly curved orbit. The electron clouds formed in this way have defects or “wormholes” in their structure, the appearance and disappearance of which is accompanied by the generation of an electromagnetic wave. The magnetron of a household microwave oven emits a wave with a frequency of 2450 MHz. This frequency is most completely absorbed by H2O molecules, which was established experimentally.

A high-voltage transformer is responsible for providing energy to the magnetron - a device capable of converting the alternating current of a standard household network into high-voltage direct current. The radiation is output to the working chamber through the magnetron waveguide - a hole in the working chamber of the lamp, closed with a material transparent for a given wavelength.

The working chamber of the microwave oven is metal, equipped with a hermetically sealed metallized door. As a rule, it is also equipped with a rotating table designed for uniform heating of food.

There is also a control unit responsible for selecting the power and operating time of the magnetron. The adjustment of the furnace power is interesting. The magnetron produces a constant amount of energy per unit time. The change in power characteristics is achieved by a certain number of switches on and off of the emitter per minute. This method is called pulse width modulation. Depending on the model, the microwave oven can be equipped with a quartz or heating element grill and a blower fan to implement the convection cooking mode.

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A little history

The patent for the first magnetron was issued in 1924 to the Czech physicist A. Zacek. Shortly thereafter, operating models were created in the USSR and Japan. For a long time, magnetrons were used as sources of centimeter-wave radio waves for radar systems.

The patent for the first microwave oven was received by American physicist Percy Spencer. While working in the laboratory to improve the radar system, Spencer forgot his sandwich on the magnetron that was on. After some time, his attention was attracted by the appetizing smell of toasted bread, cheese and bacon.

In 1949, serial production of microwave ovens began for military orders. The first model was as tall as a man, weighed 340 kilograms and cost up to $3,000. With a power of 3 kW, it was used exclusively for quickly defrosting food.

In the USSR, the first microwave ovens appeared in the early 80s of the twentieth century. Production was established at the ZIL and Yuzhmash factories. Later the production was mastered by the Tambov Elektropribor and the Dneprovsky Machine-Building Plant.

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Legends and myths associated with the microwave

Like any widespread household appliance, the microwave oven has acquired not only supporters, but ardent opponents of any “devilishness”. In their mouths, an innocent piece of tin and a coil of wires acquired truly terrible properties that poor Percy Spencer had no idea about.

• A microwave oven will turn into a bomb if you place any iron object inside and press the power button. It’s not true, it’s just that beautiful, but absolutely safe sparks, provoked by Foucault’s stray currents, run in the working chamber.
• If you turn on the stove with the door open or not tightly closed, powerful microwave radiation will destroy all electronics within a radius of several meters. It’s not true, it’s not recommended to cook mobile phones in the microwave, and only because of the difficult-to-remove smell of burnt plastic.
• Eggs in their shells should not be boiled in the microwave. No, you can. True, it’s a little difficult to wash the working chamber afterwards. The steam generated from boiling the white and yolk will break the shell and scatter the contents throughout the oven.

And in conclusion

We hope that after reading this material the reader has a clearer understanding of the physical principles underlying the operation of a microwave oven. Which, in turn, will allow you to get rid of funny, but persistent fears and phobias of ordinary and extremely useful household appliances!

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Good day to all blog readers. Today let's talk about an indispensable assistant in the kitchen - a microwave oven. I am sure this electrical appliance helps many housewives. Do you know about all its useful functions? Let's look at whether a microwave oven can be dangerous and how the device operates. What types of models are there today?

Agree, but this device makes our life a lot easier. And its ease of use allows even children to operate it. The microwave is a great time saver. You can heat up a bowl of soup in a couple of minutes. And defrost the food in 5-30 minutes. Many people use the device exclusively for defrosting and heating. But in vain, you can cook very tasty dishes in it. And if the device has convection, even an oven. But more about this in the article “ what can you cook in the microwave».

The operating principle of the device is quite simple. The heart of any microwave oven is the magnetron. The frequency of microwaves for domestic purposes is 2450 MHz. The magnetron power in modern devices is 700–1000 W. To prevent the magnetron from overheating, a fan is often installed next to it. In addition to cooling the magnetron, it circulates air inside the furnace. This also helps food heat more evenly.

Microwaves are supplied to the oven through a waveguide. It is a channel with metal walls. They are the ones that reflect magnetic radiation. When exposed to microwaves, the molecules in food begin to move quickly. Friction arises between them, resulting in the release of heat - remember physics.

This is warm and serves to warm up the food. The peculiarity of microwaves is that they do not penetrate deeper than 3 cm. Simply put, the rest of the product is heated from the surface layer. Heat further penetrates through conduction. The product is placed on a rotating plate. Constant rotation is also meant to ensure even cooking. I found a visual video for you that demonstrates the principle of operation of a microwave oven.

The microwave door protects us from microwaves. In addition, it provides visibility. It has a special design - it consists of glass plates, between which there is a metal mesh. This mesh perfectly reflects microwaves into the oven. Small holes allow you to monitor cooking, but they do not allow microwaves to pass through.

There is a special seal around the perimeter of the door. It also protects us from microwaves. If the seal is damaged, the device cannot be used.

Since metal reflects microwaves, dishes made from it are generally not suitable for cooking in an oven. In general, I also learned a lot about the features of using various utensils. I described this in the article “”.

Who came up with this “miracle”?

Having disassembled the structure of the microwave and how it works, let's take a short historical excursion.

Housewives owe this device to the American engineer P. B. Spencer. It was he who patented the microwave oven in 1946. The discovery is believed to have happened by accident. Spencer made radar equipment. And one fine day, while conducting an experiment with a magnetron, I melted a chocolate bar in my pocket. This is how the unique property of the magnetron was discovered - to heat food.

For ordinary housewives in Europe, the microwave oven became available only in 1962. Then the Japanese company Sharp began producing household microwave ovens for heating food. In the Soviet Union, it came into use by ordinary housewives even later. Only in 1978 this device was released to the masses. However, not everyone could afford it. The first microwave ovens cost about 350 rubles. The average salary was only 200 rubles.

Gradually the prices for these products decreased. The design of the device has been improved. Microprocessors appeared that made it possible to select different cooking modes. The oven began to not only heat food. Or use it to defrost them, but also cook them. When microwave ovens began to be equipped with grills, this device became even more popular. The latest technology is convection ovens. In such a microwave you can cook the most complex dishes. Thanks to convection, the device becomes a full-fledged oven.

What types of microwave ovens are there?

Now let's talk about the different types of this device. This will help you make your choice if you want to buy yourself a microwave. Conventionally, all electrical appliances of this type can be divided into:

• with grill;
• with convection;
• with inverter;
• with uniform distribution of microwaves;
• mini microwaves.

Now let’s take a closer look at the features of each type.

Microwave with grill

This oven is equipped with a heating element. There are two types of such elements: PETN and quartz. The heating element heater can be installed in different places. It can be on top, on the side wall, located at an angle, etc. Ten is reliable and has a low cost.

The quartz heating element can only be installed in one position. It is placed at the top of the oven. It is more powerful than heating element, does not take up much space, and is easy to maintain. But it also has its drawbacks. A stove with it costs more, and it is less reliable.

A microwave with grill function allows you to cook meat with a golden brown crust. Make barbecue and hot sandwiches.

Convection microwave oven

The presence of this mode will be useful for those who love to bake. Convection in a microwave allows you to cook using hot air. It circulates around the dish. Thanks to this, it bakes more evenly. This is especially important for baking. The device in this case operates in microwave and convection mode. Food cooks faster, so vitamins are better preserved.

Microwave with inverter

In a conventional microwave, the power is regulated by periodically turning on/off microwave radiation. As a result, food often becomes dry. Inverter control allows you to smoothly regulate power. The built-in inverter is responsible for this. This continuous microwave exposure preserves the texture and all the beneficial substances of the products.

Inverter microwaves work almost like ovens. Food is cooked naturally, without overheating. This type of household appliance appeared recently and quickly became popular.

With even microwave distribution

The disadvantage of household microwave electrical appliances is the uneven distribution of microwaves. As a result, the food may be too hot in one part and lukewarm in another. This occurs due to the concentration of microwaves in one part of the dish. To eliminate this drawback, manufacturers began to use three radiation sources instead of one.

Due to this, microwaves are distributed in different directions. They are reflected from the walls of the oven and penetrate the product from all sides. I-wave technology is very popular today. It ensures the propagation of microwaves in a spiral. The heat penetrates both the edges of the dish and the center. Attention is also paid to the design of the inner wall of the microwave. It helps microwaves to be reflected throughout the interior of the device.

Mini microwaves

Usually these are solo ovens, which are designed for defrosting and heating food. You can cook only the simplest dishes in them. In general, they are not intended for this. The main advantage of such a micro-stove is its size. small microwaves don't even have a rotating plate.

This oven saves energy and does not take up much space in the kitchen. If you only plan to heat or defrost food in it, this is the best choice.

Built-in models of microwave ovens

Separately, I would like to highlight built-in models. They can be convection, grill, inverter or evenly distributed microwaves. The main advantage is the design. You can choose either a stylish or simply ergonomic model. It can fit perfectly into any kitchen and even become its highlight.

Most often, microwaves are located in wall cabinets. This is the top row of furniture above the work area. Although a microwave oven can be built underneath, it all depends on personal preference. It is very convenient to arrange built-in devices in a column, one above the other. Most models of built-in stoves have dimensions d/w - 60 cm by 35 cm. I wrote about them in more detail in the article “ built-in microwave».

For the most part, this technique is multifunctional. Built-in models have touch controls, several cooking and power modes. The doors in such devices can open either to the left or to the right. This is very convenient; you can choose the device for a specific place in the kitchen. So that opening doors do not interfere.

I hope my review will help you decide on purchasing a new assistant. As for harm, there is a lot of conflicting information about this. You can find articles saying that radiation causes cancer, etc. I ask you not to panic. Of course, microwaves can have an effect on our body. Therefore, it is better not to be near the microwave while cooking.

The main thing is that you should not dry your beloved cat in it... :) This is an assistant that is indispensable when you need to cook quickly. A microwave oven is just an addition to the main stove and oven. But very useful and necessary. What do you think?

History of invention.

The invention of the microwave oven is an invention in a completely new way cooking.

In the 30s of the 20th century, work was carried out simultaneously in different countries to obtain powerful radio waves microwave range. These radio waves were primarily used in radars. Quite by accident, in 1932, employees of a laboratory in the United States fried two sausages without fire, placing them near a powerful microwave generator.

In 1945, the American engineer Spencer experimented with a magnetron - a radio tube that generates radio waves in the microwave range. Spencer took several grains of corn and placed them near the magnetron, after a few minutes the grains turned out to be popcorn. He did the same with a raw egg.

A raw egg, left cold on the outside, boiled almost instantly in the middle under the influence of electromagnetic waves.

In October 1945, the company where Spencer worked received a patent for the microwave oven and began producing devices called "radar ovens" - large cabinets filled with radio tubes, transformers and cooling fans. The space where the food had to be placed was no larger than a regular kitchen oven. We used these microwave ovens to defrost strategic food stocks.

In 1952, the Japanese bought a patent and started producing microwave ovens for the home.

And fifteen years later, our domestic microwave ovens appeared in stores.

Gradually, microwave ovens became combined and were equipped grill, convector, “crisp” and other additional functions, with the help of which cooking has been simplified, and the taste is equal to dishes prepared in the traditional way.. A microwave can cook food in five different ways: simple microwaves; grill radiation; microwave and grill at the same time; grill using convection; Microwave with convection.

Where do microwaves come from?

Household microwave ovens use microwaves with a frequency of 2450 MHz. This frequency is established for microwave ovens by special international agreements, so as not to cause interference operation of radars and other devices using microwaves.

The radiation source is a high voltage vacuum device - magnetron. A high voltage must be applied to the magnetron filament - about 3–4 kV. The mains supply voltage (220 V) is not enough for the magnetron, and it is powered through a special high voltage transformer.

The magnetron power is approximately 700–850 W. To cool the magnetron, there is a fan next to it that continuously blows air over it. The fan provides forced convection of air in the oven cavity while simultaneously heating it, which promotes uniform baking of products.

Microwaves from the magnetron enter the furnace through a waveguide - a channel with metal walls that reflect microwave radiation.

Complex design has a microwave door. It should provide visibility (what is happening inside) and prevent microwaves from escaping outside. This is a multilayer “pie” made of glass or plastic plates.

Between the plates there must be a mesh of perforated metal sheet. The metal reflects microwaves back into the oven cavity, and small perforation holes (less than 3mm) do not allow microwave radiation to pass through. A seal made of dielectric material is mounted around the perimeter of the door.

For microwave cooking completely unsuitable metal utensils. Microwave do not penetrate metal, they are reflected from it. This may cause electric discharge (arc) and cause damage to the oven. Besides, reflected microwaves can pass through glass doors, which is unsafe for health

How do microwaves heat food?

To heat food using microwaves, it must be present dipole molecules, that is, those that have a positive electrical charge at one end and a negative one at the other. There are many such molecules in food - these are molecules of fats, sugars and water. In an electric field, they line up strictly in the direction of the field lines, “plus” in one direction, “minus” in the other. As soon as the field changes direction to the opposite direction, the molecules immediately turn over at 180°. The wave field in which these molecules are located changes polarity 4,900,000,000 times per second!

Under the influence of microwave radiation, molecules rotate at a frantic frequency and rub against each other. The heat released during this process is what causes the food to warm up. Heating of products occurs due to the heating of the surface layer by microwaves and further penetration of heat into the depths of the food due to thermal conductivity.

Water boils in the microwave not like in a teapot, where heat is supplied to the water only from below. Microwave heating comes from all sides. In the microwave, the water will reach boiling temperature, but there will be no bubbles. But when you take the glass out of the oven, shaking it at the same time, the water in the glass will belatedly begin to boil, and the boiling water can scald your hands.

If you want to bring water to a boil in a glass or other tall, narrow vessel, be sure to drop a teaspoon into it before placing the glass in the oven.

What should you not do?

You cannot turn on an empty oven, without a single object that would absorb microwaves. Without encountering any obstacles on their way, microwaves will be reflected repeatedly from the inner walls of the oven cavity, and the concentrated radiation energy can disable the oven. As a minimum load, you need to put at least a glass of water in it.

Are microwaves dangerous?

Microwaves do not have any radioactive effect on biological tissues or food.

Microwave cooking requires very little fat, so microwaved food healthier and does not pose any danger to humans.

The design of the furnace includes strict measures to prevent radiation from escaping outside. Although direct exposure to microwaves can cause burns, there is a risk when using a working microwave properly completely absent.

Microwaves decay very quickly in the atmosphere. And already at a distance of half a meter from the microwave, the radiation becomes 100 times weaker. It is enough to move away from the stove at arm's length, and you can feel in complete safety.

Bon Appetit everyone!

Magazine "Science and Life"

The main part in any microwave oven is the magnetron. A magnetron is a special vacuum tube that creates microwave radiation. Microwave radiation has a very interesting effect on ordinary water, which is found in any food.

When irradiated with electromagnetic waves with a frequency of 2.45 GHz, water molecules begin to vibrate. As a result of these vibrations, friction occurs. Yes, normal friction between molecules. Friction generates heat. It heats the food from the inside. This is how you can briefly explain the principle of operation of a microwave oven.

Microwave design.

Structurally, a microwave oven consists of a metal chamber in which food is cooked. The chamber is equipped with a door that prevents radiation from escaping. To heat food evenly, a rotating table is installed inside the chamber, which is driven by a gearbox (motor), which is called T.T.Motor (Turntable motor).

Microwave radiation is generated by a magnetron and fed into the chamber through a rectangular waveguide. A fan is used to cool the magnetron during operation. F.M. (Fan motor), which forces cold air through the magnetron. Next, heated air from the magnetron is directed through the air duct into the chamber and is also used to heat food. Through special non-radiating holes, part of the heated air and water vapor is discharged outside.

Some models of microwave ovens use a dissector, which is installed in the upper part of the microwave chamber, to create uniform heating of food. Externally, the dissector resembles a fan, but it is designed to create a certain type of microwave wave in the chamber so that food is evenly heated.

Electrical diagram of a microwave oven.

Let's take a look at a simplified electrical diagram of a typical microwave (click to enlarge).

As you can see, the circuit consists of a control part and an executive part. The control part, as a rule, consists of a microcontroller, display, push-button or touch panel, electromagnetic relays, and buzzer. These are the "brains" of the microwave. In the diagram, all this is shown as a separate board with the inscription Power and Control Curcuit Board . A small step-down transformer is used to power the control part of the microwave. In the diagram it is marked as L.V.Transformer (only the primary winding is shown).

The microcontroller controls electromagnetic relays through buffer elements (transistors): RELAY1, RELAY2, RELAY3. They turn on/off the actuating elements of the microwave oven in accordance with a given operating algorithm.

The actuators and circuits are a magnetron (Magnetron), a table motor reducer T.T.Motor (Turntable motor), a cooling fan F.M ( Fan Motor), grill heating element ( Grill Heater), backlight lamp O.L ( Oven Lamp).

We especially note the executive circuit, which is a microwave radiation generator.

This circuit begins with a high-voltage transformer ( H.V.Transformer ). It's the healthiest in the microwave. Actually, this is not surprising, because through it you need to pump the power of 1500 - 2000 W (1.5 - 2 kW) required for the magnetron. The output (useful) power of the magnetron is 500 - 850 W.

An alternating voltage of 220V is supplied to the primary winding of the transformer. An alternating filament voltage of 3.15V is removed from one of the secondary windings. It is connected to the filament winding of the magnetron. The filament winding is necessary for the generation (emission) of electrons. It is worth noting that the current consumed by this winding can reach 10A.

Another secondary winding of the high voltage transformer, as well as a voltage doubling circuit on the high voltage capacitor ( H.V.Capacitor ) and diode ( H.V. Diode ) creates a constant voltage in 4kV to power the magnetron anode. The anode current is small and amounts to about 300 mA (0.3A).

As a result, electrons emitted by the filament winding begin to move in a vacuum.

The special trajectory of electrons inside the magnetron creates microwave radiation, which is what we need to heat food. Microwave radiation is removed from the magnetron using an antenna and enters the chamber through a section of a rectangular waveguide.

This simple, but very sophisticated circuit is a kind of microwave heater. Do not forget that the microwave oven chamber itself is an element of this microwave heater, since it is, in fact, a resonator in which electromagnetic radiation occurs.

In addition to these elements, the microwave oven circuit has many protective elements (see KSD thermal switches and similar ones). For example, a thermal switch controls the temperature of the magnetron. Its standard operating temperature is somewhere between 80 0 - 100 0 C. This thermal switch is mounted on the magnetron. By default it is not shown in the simplified diagram.

Other protective thermal switches are labeled on the diagram as OVEN THERMAL CUT-OUT(installed on the air duct), GRILL THERMAL CUT-OUT(controls grill temperature).

If there is an emergency and the magnetron overheats, the thermal switch opens the circuit and the magnetron stops working. In this case, the thermal switch is selected with a small margin - for a shutdown temperature of 120 - 145 0 C.

Very important elements of the microwave oven are three switches, which are built into the right end of the microwave oven chamber. When the front door is closed, two switches close their contacts ( PRIMARY SWITCH- main switch, SECONDARY SWITCH- secondary switch). Third - MONITOR SWITCH(control switch) - opens its contacts when the door is closed.

A malfunction of at least one of these switches will result in the microwave not working and the fuse (Fuse) tripping.

To reduce the interference that enters the electrical network when the microwave oven is running, there is a surge filter - NOISE FILTER.

Additional microwave elements.

In addition to the basic design elements, the microwave can be equipped with a grill and a convector. The grill can be made in the form of a heating element (heating element) or infrared quartz lamps. These microwave elements are very reliable and rarely fail.

Grill heating elements: metal-ceramic (left) and infrared (right).

The infrared heater consists of 2 infrared quartz lamps connected in series at 115V (500 - 600W).

Unlike microwave heating, which occurs from the inside, a grill creates radiant heat that heats the food from the outside in. The grill heats up food more slowly, but without it you can't cook crispy chicken.

A convector is nothing more than a fan inside the chamber, which works in tandem with a heater (heating element). The rotation of the fan ensures the circulation of hot air in the chamber, which contributes to uniform heating of food.

About the fuse diode, high-voltage capacitor and diode.

The elements in the magnetron power circuit have interesting properties that need to be taken into account when repairing a microwave oven.

For those who want to understand the structure of microwave ovens in more detail, an archive with service instructions for microwave ovens (Daewoo, SANYO, Samsung, LG) has been prepared. The instructions contain schematic diagrams, disassembly diagrams, recommendations for checking elements, and a list of components.

A microwave oven is one of the indispensable appliances in the kitchen, without which housewives today find it difficult. Everyone knows perfectly well how to use it: place the dish, press 1-2 buttons and wait 2-3 minutes, after which all that remains is to take out the already heated food. However, few people understand the principle of operation of a microwave, that is, how its main elements work. Let's try to understand this issue.

How does a microwave oven work?

All microwave ovens operate on the same principle, and the main element is a magnetron - a special device capable of emitting short waves with a frequency of 2450 MHz. In modern devices its power is 700-1000 W. Note that during operation it gets very hot, so a fan is installed near it, which performs several functions at once: first of all, it removes heat from the magnetron, and secondly, it ensures air circulation in the microwave oven chamber. In turn, this ensures even heating of the food.

Actually, the entire principle of operation of a microwave is based on this: the magnetron delivers short waves with a high frequency, which affect the food and heat it up. Of course, such an explanation is primitive, but it also makes it possible to understand the essence of the process.

More detailed explanation

Microwaves emitted by the magnetron pass into the oven chamber through a special waveguide - a channel with metal walls that reflect magnetic radiation. Once these waves enter the chamber, they affect the food, or more precisely, the water molecules that are contained in any food product. As a result, dipoles (molecules) under the influence of microwaves begin to move quickly and rub against each other, which contributes to the release of thermal energy. This is how food is heated.

The peculiarity of microwaves is that they can penetrate up to 3 centimeters deep. The remaining volume of the product is heated from the top layer. This principle of operation of the magnetron in a microwave explains why, after heating, food can be hot on top and at the same time cold inside. Heat penetrates deeper due to natural thermal conductivity.

If you have used a similar device before, you could not help but notice that it rotates during the heating process. This is necessary to ensure that the microwaves reach all areas of the food being heated.

Microwave protection

Considering the principle of operation of a microwave oven, it is logical to think about its harm to human health. Of course, microwaves emitted by a magnetron are harmful to humans. However, after opening the door, the magnetron stops working, so a person physically cannot feel their influence. And to ensure that they do not go beyond the heating chamber, special protection is provided. All its walls are made of metal, which reflects waves, and they cannot leave the device. As for the glass door (it simply must be so that the user can see the heating or cooking process), it is covered with a special mesh that reflects microwaves. If this grid is removed, then the waves can leave the chamber space, and this can really harm a person. It is unacceptable to use the microwave oven if there is damage, for example, to the door seal or its mesh.

By the way, given the fact that metal reflects microwaves, it is unacceptable to use metal utensils.

Device design

All microwave ovens work the same way, therefore, they have the same composition of parts. In particular, the following structural elements can be distinguished:

1. Magnetron is the main unit that is the source of microwaves.
2. A chamber with a rotating podium and metal walls that reflect radio waves.
3. Transformer for increasing voltage.
4. Door with protective mesh and transparent glass.
5. Communications and control circuit.
6. Waveguide.
7. Fan for cooling the magnetron.

All these elements take part in one way or another in the operation of the furnace.

Magnetron operation

As already mentioned, the magnetron is the heart of the microwave oven. It is an electric vacuum diode made of a large cylindrical anode. The anode itself is copper; it combines 10 sectors of the copper wall.

In the center of the device there is a rod cathode, inside the channel of which there is a filament. It is designed to emit electrons. In order for the device to generate microwaves, a magnetic field must be created in the cavity. For this, high-power ring magnets are used - they are located at the ends of the part. And to create emission, a voltage of four thousand volts is applied to the anode. To achieve this voltage, a transformer in the microwave comes into play. The operating principle of any model presupposes its presence.

There are also wire loops inside the device that connect to the cathode, which is connected to the radiating antenna. It is from this element that the microwaves enter directly into the waveguide itself, from where they exit and enter the chamber with food.

Power control

If less power is needed to cook food, the magnetron can be cycled on or off. In science, this technology is called pulse width modulation.

In order for a 400 W device to produce half of it within 20 seconds, it is activated for 10 seconds, after which the power is turned off for the same 10 seconds. Of course, all this happens with full automation.

Magnetron cooling

Note that during operation the device generates a large amount of heat, therefore, it needs to be cooled. To do this, the device itself is installed in a plate radiator, and a cooler is placed next to it. It blows on the radiator and removes heat from the magnetron. If the fan does not work, the device may simply overheat during operation and simply fail. But to prevent this from happening, it is additionally equipped with a special thermal fuse - a protective device.

Purpose of the fuse

To prevent the grill and magnetron from overheating, some models install special thermal fuses (thermal relays). They may be different. Specifically, the main difference is the amount of heat they are able to withstand.

This device is quite simple in terms of its operation. It is made of aluminum alloy and is attached using a flange connection, ensuring reliable contact with the area where the temperature is measured. There is a bimetallic plate installed inside the case, which can resist a certain temperature. And if the temperature value goes beyond a certain limit, then the plate compresses and activates the pusher, and it opens the circuit of the contact group. The supply of electricity to the unit then stops, the magnetron turns off and gradually cools down, the plate returns to its original position as the magnetron cools. After a certain time, the contacts close again.

This is the simple principle of operation of a microwave oven, in particular the overheating fuse. Note that in cheap models this element may be absent, since it is completely unnecessary for the normal functioning of the device. This is only a protection element that increases the reliability and service life of the furnace, nothing more.

The role of the cooler

When talking about how a microwave oven works, the principle of operation must be explained taking into account all the structural elements that can be used in it. Cooler is one of them. Of course, this is an important component of the system, without which the device and operation of the microwave will not be complete.

His tasks:

1. Magnetron cooling. This is the most important task, without which the magnetron would burn out on the very first day of using the furnace.
2. Cooling other components that generate heat during operation. In particular, we are talking about microcircuits.
3. In models with a grill, the cooler cools the thermostat.
4. Creating excess pressure in the chamber where the food is located. Because of this, vapors and air are removed through the ventilation ducts.

Most often, just one fan is enough to perform all these functions. Due to the presence of air duct holes in the chamber, the air itself is distributed evenly.

Camera device

In principle, the physics of how a microwave operates is not complicated, because it has been known since school that strong electromagnetic radiation is dangerous for humans. It is this that comes from the magnetron and enters the chamber with food, so this device requires a strong multi-level protection system.

The entire working chamber inside is covered with enamel, which blocks electromagnetic radiation. There is a metal casing on top that prevents waves from penetrating into the room. And to protect the glass door, a steel mesh with small cells is provided - it blocks radiation with a frequency of up to 2450 Hz and a wavelength of up to 12 cm.

Note that the door is the weakest point through which microwaves can leak, so it should fit as tightly as possible to the cabinet and have no gaps. If there is a gap, the operation of the device is prohibited. In this case, it is necessary to adjust the door hinges and return it to its original position.

In addition, the microwave operating algorithm provides for the use of a special protective device to prevent it from being turned on with the door open. Such a system can be implemented in different ways, most often microswitches are used to control the position of the door. These switches can turn off the magnetron and transmit information about the door position to the control unit.

Control Panel

It is available on any model. In older devices, the control panel is represented by just two (or even one) mechanical switches. One sets the operating mode (heating, defrosting, etc.), the other sets the time. The scheme is primitive, but working and simple.

However, modern models are equipped with a large touch panel. Such control panels provide the user with great functionality and even the ability to program the mode. For example, you can set a specific start time for heating food, the duration of the process, you can even specify the food or dishes that will be heated. And although it seems that such devices are more advanced, in technical terms there are few differences. The electronic control panel does not change how the microwave operates.

Control block

There is a command device in every device (not only in microwave ovens), where at a certain moment one or another action must be performed. Thanks to it, various functions are provided. In particular, the device can use it to maintain a given temperature, turn the oven on or off after a given operation.

In older microwave ovens, this device is presented in the form of two electromechanical switches - they are responsible for the functions described above and play an important role in the overall structure of the microwave. Of course, over time, electronics have evolved, resulting in fully electronic control units. Nowadays, microwave ovens (and not only them) use microprocessors and special programs, according to which the device can perform one or another function:

1. Built-in clock.
2. Defrosting food.
3. Sound signal when defrosting, cooking or heating food is complete.

Conclusion

Now you have a better understanding of how a microwave works. The operating principle of this device is relatively simple. It is based on the elementary laws of physics.

Let's consolidate what we have learned: the magnetron (the main element of a microwave oven) emits very short radio waves with a high frequency. They affect water molecules, causing them to begin to actively move. This process is accompanied by the release of heat. Considering the fact that the waves penetrate shallowly into the food, only the surface of the food is heated, and then, due to natural thermal conductivity, the heat moves deeper.

This is the basic principle of operation of a microwave oven. We also reviewed the device and main elements in this article. All of them are classic and are used in absolutely all models from any manufacturer. At the moment, the working scheme described above is the only one, although different manufacturers may use modules that differ in some parameters. For example, one model may use a more powerful magnetron, which can heat food much faster. In other compact models, this element may have low power, which allows you to create a small device. There are hundreds of similar differences, but the principle of operation does not change at all. Of course, a stronger magnetron determines how long the microwave operates to heat food of the same volume. Therefore, if you don’t like to wait, then it is better to choose a more powerful model.

That's all. We have completely disassembled the structure of this piece of household appliance and answered most of the questions related to it.