Composition of a microwave oven. Is a microwave oven harmful to health and how to check it. Control unit: microwave operating principle

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 of her 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 it for you visual video, which 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 choose different modes cooking. 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 different types 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.

Quartz a 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. Device in 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 household appliances appeared recently and became popular very quickly.

With even microwave distribution

The disadvantage of household microwave electrical appliances is uneven distribution 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 plan to only 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 even microwave distribution. 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 top row 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?

Microwave ovens have been part of our everyday life for a long time, but debates about their usefulness and safety are still ongoing. It is curious that, solving such issues on various forums and in personal meetings, the vast majority do not even approximately imagine the principle of operation of a microwave.

That is why, before asking yourself whether it is your friend or foe, it makes sense to find out what this amazing unit is, capable of boiling a glass of water or cooking a chicken without using a visible heat source. Almost everyone has seen a microwave in operation, but few people imagine how it does it.

Action and principle of operation

The principle of operation of a microwave oven is implied in its name - the effect on the body (in this case, food) of microwave radiation (microwave radiation or simply microwave). Under the influence of high-frequency electromagnetic oscillations, products are heated to high temperatures, which makes it possible to heat or even cook dishes without the use of classic thermal heaters. By the way, this same method is used not only for preparing food products, but also for heat treatment of technical products: annealing and hardening, say, drills, gears, knives, etc.

The main condition necessary for a microwave oven to operate is the presence of so-called polar molecules in the object. It is they who are affected by the electromagnetic field of the device. Fortunately, almost all food products (with the possible exception of completely dehydrated ones) contain water, which consists of such molecules. Once in a powerful alternating electromagnetic field, such molecules begin to quickly change their position, following the constantly changing direction of the magnetic field. During the process of rotation, these molecules literally rub against each other, and everyone knows what happens. Try quickly rubbing your palms against each other - do you feel the warmth?

Thanks to the alternating electromagnetic field, polar water molecules begin to rotate rapidly.

The main difference between the effect of microwave radiation on an object and ordinary friction or heating with an open flame is that not only the surface of the object is heated, but also its deep layers. This is due to the fact that microwave radiation acts not only on the surface of an object, but also penetrates deep into it, causing molecules to move and heat up.

The penetration depth depends on the radiation frequency. And for standard microwave ovens operating at a frequency of 2.4 GHz, it is 1.5–2.5 cm. It is not difficult to guess that, for example, a pie placed in a microwave oven will warm up completely and evenly both inside and outside. Moreover, he will do this in the shortest possible time, since the rate of heating of the body in the microwave field is 0.3-0.5 degrees per second. 10 seconds - +5 degrees. Minute - +30 degrees.

Advantages and disadvantages

So, it’s time to formulate the main differences between microwave heating and classical heating:

The only seemingly drawback inherent in microwave ovens is the impossibility of frying, but the designers solved this issue by equipping the device with conventional thermal electric heaters, like an electric oven. With their help you can easily fry the product. In addition, there are so-called Crusty plates, made of a special material that is safely heated by microwave currents. Place a chop on such a plate and the stove will not only cook it quickly, but also fry it, since this pan heats up to 200 degrees.

Microwave oven device

Now it's time to figure out how a microwave works. The heart of any such stove is a special generator that creates a high-frequency electromagnetic field of high intensity. It's called a magnetron. Next, the field created by it is directed to the product chamber using specially designed waveguides. He does this in such a way that the entire internal volume of the chamber is “filled” with the field evenly, ensuring high-quality heating of products of any volume. Additionally, this is facilitated by the rotating tray that most microwave ovens are equipped with.

The magnetron occupies the most honorable place under the lid of the device.

Controls the operation of the RF generator the electronic unit, assembled on a microprocessor. The microprograms built into the unit allow you to set the desired cooking mode, control the temperature in the chamber, humidity, and cooking time. They also monitor the safety of using the stove - whether the protective door is closed, whether there is an insulation breakdown, whether the temperature inside the chamber has risen above critical, etc. The controller is controlled from one type of remote control or another - push-button, touch, etc. And, of course , the furnace also has a power supply that supplies energy to all the electronics and the magnetron itself.

Danger and harm of microwave ovens

And now the most important question that worries almost every microwave owner: does the device pose any danger to others? There are many myths about the dangers of using microwaves. technologies in everyday life. The main ones:

1. Radiation hazard.
2. Electromagnetic radiation hazard.
3. Poor influence of microwaves on the quality of prepared products.
4. Possibility of physical damage by a microwave field.
5. Increased risk of injury electric shock high voltage.

Radiation damage

According to this myth, everyone who is near a microwave oven receives radiation exposure. Moreover, even when the stove is turned off, it “radiates” no worse than a Chernobyl tractor. But if you believe the basics of nuclear physics (everyone took it in school), the radiation that everyone is so afraid of and that really poses a danger is ionizing radiation.

Take a look at the list, which lists the types of electromagnetic radiation, arranged in descending order of their wavelength:

1. radio waves - 10 km - 0.1 mm;
2. infrared radiation- 1 mm - 780 nm;
3. visible radiation (light) - 780 - 380 nm;
4. ultraviolet radiation - 380 - 10 nm;
5. X-ray radiation - 10 - 5 pm;
6. hard (gamma) radiation - less than 5 pm.

Of the entire list, only the last two items are fully ionizing and partially ionizing - the third from the bottom (UV light). And only gamma radiation can leave behind induced radiation. Wavelength electromagnetic field microwave oven - 12 cm. It is much more logical to be afraid of the visible light emitted by the Ilyich light bulb, the ionizing ability of which is 3 orders of magnitude higher than the radiation of a microwave oven. But, despite the obvious, no one is afraid of light bulbs, almost everyone is afraid of microwave ovens.

Does high-frequency radiation change the properties of products.

There is an opinion that, after being in the microwave, products change their physical structure. Some connections are supposedly destroyed, others appear, the charge, pole, degree, memory changes - whatever. After all this disgrace, healthy foods turn into poison.

Microwave radiation, as mentioned above, affects polar molecules, which are water molecules. Today, science knows for certain that water is an amorphous body and has no structure at all unless it is in a frozen state. How can this very structure change if the amorphous body does not have it at all?

The birth of such a myth is most likely associated with the concept of “structured water”, which appeared thanks to all sorts of pseudosciences such as homeopathy and “businessmen” selling “charging” water trays and other technological wonders of parallel worlds.

Electric shock

How electrically safe is the device?.

The fear that a microwave oven is dangerous in terms of electric shock is, in principle, understandable. To operate the magnetron, a high voltage source is required - about 4 kV. If we add to this the power of a modern microwave, which can reach a kilowatt, then all the horror of a person who is far from electricians becomes understandable. Nevertheless, this same person quite calmly uses a one and a half kilowatt vacuum cleaner and a two kilowatt electric stove.

Remember the ordinary CRT TV, which has served us for decades and continues to serve us to this day. Accelerating anode voltage its kinescope reaches 30 kV. This is almost an order of magnitude higher than the voltage on the magnetron. If you open the microwave, you can get energized. But also on TV back cover with just four screws! Now think about it: how many of your friends have been electrocuted by an evil TV? Thus, in terms of electrical safety, a microwave oven is no different from any other household appliance.

Is microwave radiation harmful to the body?.

Yes, microwaves are harmful to humans. But a lot of modern devices operate at the same frequency: Wi-Fi modem, mobile phone, smartphone. Working with them is considered safe. Is microwave radiation harmful or harmless? Harmful, but only when exceeding a certain level. Your mobile phone emits radiation, but its transmitter power is low. Even though you keep it close to your temple, periodic conversations on the phone will not cause any particular harm to your health. Another thing is the microwave oven. The power of its “transmitter” reaches thousands of watts.

But, firstly, unlike a mobile phone, the magnetron radiation is not directed in all directions, but into the working chamber. Secondly, and this is the main thing, the chamber, like its door, has a special coating that prevents radiation from escaping beyond the working area. Of course, the coating does not block microwaves 100%, but this is not necessary. You don’t hold the microwave to your temple like a telephone, and you don’t use it with your nose buried in the door for hours. In addition, the microwave intensity decreases in proportion to the square of the distance.

What do the numbers say about this? We open medical documents that standardize the maximum permissible microwave radiation that is safe for humans and read: no more than 10 μW/cm2. Is it a lot or a little? It's time to look at the picture below:

Near the microwave oven door itself, the electromagnetic field strength is quite high - 5 mW/cm2. But already at a distance of half a meter it weakens by two orders of magnitude, and at a distance of one and a half meters it is twice as low as the maximum permissible level. Thus, if you don’t literally hug the microwave on and don’t use it around the clock, then you don’t have to worry about your health. But can the door be opened? It is possible, but the magnetron will immediately turn off, since it has foolproof protection. The same protection will not allow you to put your hand in(and for some, even the head) into a working device in order to check its serviceability “by touch”.

As soon as you open the door, the automation will remove power from the magnetron.

Thus, a working microwave oven, subject to elementary rules operation, described in detail in the attached instructions, is absolutely safe for humans.

Microwave ovens (microwave ovens) have long become the most common household appliance, with the help of which you can very quickly defrost food, reheat already cooked food or prepare a dish according to an original recipe, and even disinfect kitchen cleaning sponges and rags that do not contain metal.

Having a convenient, intuitive clear interface, as well as multi-level protection, allow even a child to cope with the control of such a complex and high-tech device as a microwave oven. Some dishes can be easily and quickly prepared using built-in programs. A possible malfunctions can be completely eliminated by doing .

Heating of products placed in the microwave chamber occurs due to exposure to powerful electromagnetic radiation in the decimeter range. In household appliances, a frequency of 2450 MHz is used. Radio waves like this high frequency penetrate deep into the products and affect polar molecules (in products it is mainly water), causing them to constantly shift and line up along the electromagnetic field lines.

This movement increases the temperature of the food, and heating occurs not only from the outside, but also to the depth to which radio waves penetrate. In household microwave ovens, the waves penetrate 2.5-3 cm deep, they heat the water, which, in turn, heats the entire volume of food.

The magnetron device is the main component

Radio waves with a frequency of 2450 MHz are generated by a special device - magnetron, which is an electric vacuum diode. It has a massive copper cylindrical anode, round in cross-section and divided into 10 sectors with the same copper walls.

In the center of this structure there is a rod cathode, inside of which there is a filament. The cathode serves to emit electrons. At the ends of the magnetron there are powerful ring magnets, which create a magnetic field inside the magnetron necessary for generating microwave radiation.

A voltage of 4000 Volts is applied to the anode, and 3 Volts to the filament. There is an intense emission of electrons, which are picked up by a high-intensity electric field. The geometry of the resonator chambers and the anode voltage determine the generated frequency of the magnetron.

Energy is collected using a wire loop connected to the cathode and led into the emitter-antenna. From the antenna, microwave radiation enters the waveguide, and from it into the microwave chamber. Standard output power magnetrons used in household microwaves is 800 W.

If less power is required for cooking, this is achieved by turning on the magnetron for certain periods of time, followed by a pause.

To obtain a power of 400 W (or 50% of the output power), you can turn on the magnetron for 5 seconds and turn it off for 5 seconds during a 10-second interval. In science it's called pulse width modulation.

The magnetron emits during operation a large number of heat, so its body is placed in a plate radiator, which during operation should always be blown by an air flow from the fan built into the microwave. When overheated, the magnetron very often fails, so it is equipped with protection - a thermal fuse.

Thermal fuse and why it is needed

To protect the magnetron from overheating, as well as the grill, which is equipped with some models of microwave ovens, special devices called thermal fuse or thermostat. They are available in different temperature ratings, indicated on their body.

The operating principle of a thermal relay is very simple. Its aluminum body is attached using a flange connection to the place where it is necessary to control the temperature. This ensures reliable thermal contact. Inside the thermal fuse there is a bimetallic strip that has settings for a certain temperature.

When the temperature threshold is exceeded, the plate bends and actuates a pusher, which opens the plates contact group. The power supply to the microwave oven is interrupted. After cooling, the geometry of the bimetallic plate is restored and the contacts close.

Purpose of microwave oven fans

The fan is the most important component of any microwave, without which its operation would be impossible. It performs a number of important functions:

• Firstly, the fan blows main detail Microwave ovens use a magnetron, ensuring its normal operation.
• Secondly, other components electronic circuit They also generate heat and require ventilation.
• Thirdly, some microwave ovens are equipped with a grill that is necessarily ventilated and protected by a thermostat.
• And finally, the food being cooked in the chamber also generates a large amount of heat and water vapor. The fan creates a slight excess pressure in the chamber, as a result of which the air from the chamber along with heated water vapor comes out through special ventilation holes.

In the microwave, from one fan, which is located at the rear wall of the case and sucks in air from outside, a ventilation system is organized using air ducts, directing the air flow to the magnetron plates and then into the chamber. The fan motor is a simple single phase AC motor.

Microwave oven protection and locking system

Any microwave oven has a powerful radio-emitting device inside - a magnetron. Microwave radiation of such power can cause irreparable harm to the health of humans and all living beings, so it is necessary to take a number of protective measures.

The microwave has a completely shielded metal cooking chamber, which is additionally protected from the outside metal body, preventing high-frequency radiation from penetrating outside.

The transparent glass in the door has a screen made of a metal mesh with a fine mesh, which does not allow radiation of 2450 Hz, wavelength 12.2 cm, generated by the magnetron, to pass out.

The issue of saving energy consumption has always been relevant. one of the types lighting fixtures, which will greatly help reduce household electricity consumption, are. To make the best choice, you just need to understand the advantages and disadvantages of each type of such lamps.

Due to their features, double switches are widely used at home. How to properly connect such switches and what you need to know to prevent errors in this case can be read in.

The microwave door fits tightly to the cabinet and it is very important that this gap maintains its geometric dimensions. The distance between the metal body of the camera and the special groove in the door should be equal to a quarter of the wavelength of microwave radiation: 12.2 cm/4 = 3.05 cm.

A standing electromagnetic wave is formed in this gap, which has a zero amplitude value exactly where the door adjoins the body, so the wave does not propagate outward. This is an elegant way to solve the issue of protection from microwave radiation using the microwave waves themselves. This method of protection in science is called a microwave choke.

To prevent the microwave oven from turning on with the chamber open There is a system of microswitches that control the position of the door. Usually there are at least three such switches: one turns off the magnetron, the other turns on the backlight even when the magnetron is not working, and the third serves to “inform” the control unit about the position of the door.

The microswitches are located and configured so that they operate only when the microwave working chamber is closed.

Microswitches on the door are also often called limit switches.

The control unit is the brain of the device

Any microwave oven has a control unit and it performs two main functions:

• Maintaining the set microwave power.
• Turning off the oven after the set operating time has expired.

On older models of electric furnaces, the control unit consisted of two electromechanical switches, one of which set the power, and the other set the time period. With the development of digital technologies, electronic control units began to be used, and now microprocessor ones, which, in addition to performing two main functions, can also include many necessary and unnecessary service ones.

• Built-in clock, which can certainly be useful.
• Power level indication.
• Changing the power level using the keyboard (push-button or touch).
• Cooking or defrosting food using special programs “hardwired” into the memory of the control unit. In this case, the weight is taken into account, and the stove itself will select the required power.
• Signaling the end of the program with the selected sound.

In addition, modern models have upper and lower grills and a convection function, which are also controlled by the control unit.

The control unit has its own power source, which ensures operation of the unit in both standby and operating modes. An important component is the relay unit, which switches the power circuits of the magnetron and grill, as well as the fan, built-in lamp and convector circuits according to commands. The control unit is connected by cables to the keyboard and display panel.

An entertaining video about the operating principle of microwave ovens

Look how simple it is to explain why this amazing device works.

The microwave oven is currently very popular and is the most popular kitchen appliance. Using a microwave oven, you can not only heat or cook food, but also defrost food and even disinfect some kitchen utensils that do not contain metal. This device has become completely commonplace today.

A microwave oven is a household electrical appliance that is primarily intended for cooking or heating food in fast mode. Microwaves are also used in some industries where necessary materials need to be heated.

Unlike conventional ovens, heating of various products in this device occurs quite quickly, since radio waves are able to penetrate deep inside the products. This radically reduces the heating of any product and helps preserve all the nutrients in it.

The design of all microwave ovens consists, as a rule, of the same components. The design of microwave ovens has main and auxiliary elements. The appearance of these devices can be very diverse. Sizes, colors and functions may vary for each individual oven, they may be different.

Structure of a microwave oven:

• A chamber equipped with a rotating stage;
• The magnetron is the main element - a microwave emitter;
• Transformer;
• Metal case with a door that is locked when the device is operating;
• Management and communications scheme;
• Waveguide.

The microwave must also be equipped with a fan inside. Its purpose is very great, since without it the device itself will not work. This device ensures excellent operation of the magnetron and cools the electronic circuits.

How a microwave oven works: its types

The operation of a microwave oven is very simple, it is based on microwave radiation. The heart of every microwave oven is an element called a magnetron. It is the source of radiation. The frequency of microwaves is approximately 2450 MHz, and the power of modern microwave ovens can be 700 - 1000 W. This stove runs on electricity.

To ensure that the magnetron works well and does not overheat, a fan is installed next to it. It also circulates air inside the oven itself and promotes uniform heating of food or products.

Microwaves enter the oven through a waveguide, and then the walls, which are made of metal, reflect the magnetic radiation itself. Radiation, penetrating deep into products, causes their molecules to move very quickly. These actions promote friction, as a result of which heat is released (physics is present). This is warm and will warm up the food.

Types of electrical appliances:

• With grill;
• Convection oven;
• Inverter controlled device;
• A device with microwaves that are distributed evenly;
• Mini microwave.

The main advantage of all microwave ovens is their design. The market provides huge selection devices, you can choose either a stylish or ergonomic model. The description of these models will allow you to choose the model you like, which will become not just a decoration for the kitchen, but also its highlight. An example would be a Samsung microwave oven.

Control unit: microwave operating principle

Every microwave oven has such an important element as a control unit. It, in turn, performs two main functions: maintains the set power and turns off the device when the set time has expired. To date, technologies have developed the new kind this element is electronic.

Today, an electronic unit can support not only its basic functions, but also some additional ones. Some of them are necessary, while others are not needed at all. Many modern models have a grill, which is also controlled by a control unit.

Today, the command block is equipped with various microprocessors, which, in turn, support the functionality of other programs. Therefore, the power supply can be responsible for the operation additional functions.

Additional service functions:

• Built-in clock;
• Power indicator;
• Automatic defrost;
• An audible signal that indicates a completed operation.

The electronic unit is closely connected with the indicator panel and keyboard. The most important part of such a block is the relay block. It is responsible for the operation of the fan, convector, built-in lamp and even magnetron.

Microwave frequency: magnetron and its components

The principle of operation of a microwave oven is that when the microwave oven is turned on, the magnetron begins to release energy, and then it is converted into heat. This heat is used to heat food. Magnetron is translated as an electric vacuum diode, which consists of a copper anode. This is the most expensive part of the stove.

Heating of food that is inside the microwave occurs under the influence of electromagnetic radiation, that is, ultra-high frequency radio waves. Due to the fact that radio waves penetrate deeply into the heated product, it is heated very quickly and efficiently.

Decoding a magnetron is a device that produces great amount heat due to the frequency of radiation. The radiation frequency is 2.4 GHz. The efficiency of the magnetron is 80%, and the power consumption of this type of furnace during radiation can be 1100 W.

The magnetron device consists of the following parts:

• The cylindrical anode is its base, consisting of 10 sectors, each of them made of copper;
• In the center is a cathode with an incandescent filament;
• The end parts are occupied by magnets, they create the magnetic field necessary for radiation;
• A wire loop connected to the antenna, which emits energy.

With the help of an emitter antenna, the energy first enters the waveguide and then into the furnace chamber. The voltage supplied to the anode is 4 thousand W, the filament is 3 thousand W. The magnetron housing is located in a plastic radiator, where a built-in fan blows air over it, and a special fuse is responsible for its overheating.

Design and principle of operation of a microwave oven (video)

In English, this statement Microwave oven can be deciphered as a microwave oven. This design is a household appliance that runs on electricity and is distinguished by the fact that it defrosts or heats food very quickly. This happens due to microwave radiation.

Which in most cases simplifies daily life most people, especially those who do not like to tinker in the kitchen for a long time, and love comfort in all its details, namely - microwave oven, or as people say - microwave. In this article you will learn: what is microwave, what types of microwave ovens are there, how to choose a microwave oven, and other nuances that relate to this technique. So…

Microwave . orMicrowave ( English Microwave oven ) - a household electrical appliance designed for quick cooking or quick heating or cooking, defrosting food, and also used in production purposes for heating certain materials, for example glue.

Unlike classic ovens (for example, an oven or a Russian oven), food is heated in a microwave oven not from the surface, but throughout the entire volume of the product containing polar molecules (for example, water), since radio waves penetrate deep enough into almost all food products . This reduces the heating time of the product.

The history of the discovery of the microwave oven

Like many other discoveries that have had a significant impact on people's daily lives, the discovery of the thermal effects of microwaves happened by accident. In 1942, American physicist Percy Spencer worked in the laboratory of the Raytheon company with a device that emitted ultra-high-frequency waves. Different sources describe differently the events that happened that day in the laboratory. According to one version, Spencer put his sandwich on the device, and after removing it a few minutes later, he discovered that the sandwich had warmed up to the middle. According to another version, the chocolate that Spencer had in his pocket when he was working near his installation warmed up and melted, and, struck by a lucky guess, the inventor rushed to the buffet for raw corn kernels. The popcorn brought to the installation soon began to burst with a bang...

One way or another, the effect was discovered. In 1945, Spencer received a patent for the use of microwaves for cooking, and in 1947, the first devices for cooking using microwaves appeared in the kitchens of hospitals and military canteens, where the requirements for food quality were not so high. These Raytheon products, as tall as a man, weighed 340 kg and cost $3,000 apiece.

It took a decade and a half to perfect the oven, in which food is cooked using invisible waves. In 1962, the Japanese company Sharp launched the first mass-produced microwave oven, which, however, did not initially cause a consumer stir. The same company developed a rotating table in 1966, and used it for the first time in 1979. microprocessor system oven control, and in 1999 the first microwave oven with Internet access was developed.

The experience of using millions of microwave ovens in many countries over the past decades has proven the undeniable convenience of this method of cooking - speed, efficiency, ease of use. The very mechanism of cooking food using microwaves, which we will introduce you to below, determines the preservation of the molecular structure, and therefore the taste of the products.

The principle of operation of a microwave oven, or how food is heated using a microwave

Food contains many substances: mineral salts, fats, sugar, water. To heat food using microwaves, it requires the presence of dipole molecules, that is, those with a positive end at one end. electric charge, and on the other - negative. Fortunately, there are plenty of such molecules in food - these are molecules of fats and sugars, but the main thing is that the dipole is a molecule of water - the most common substance in nature.

Every piece of vegetables, meat, fish, and fruit contains millions of dipole molecules. In the absence of an electric field, the molecules are arranged randomly. 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, i.e. change polarity, as the molecules immediately turn over 180 o.

So, the microwave frequency that almost all microwave ovens use is 2450 MHz. One hertz is one vibration per second, a megahertz is one million vibrations per second. During one wave period, the field changes its direction twice: it was “plus”, became “minus”, and the original “plus” returned again. This means that the field in which our molecules are located changes polarity 4,900,000,000 times per second! Under the influence of microwave radiation, molecules tumble at a frantic frequency and literally rub against each other during revolutions. The heat released during this process is what causes the food to warm up.

Microwaves heat up food in much the same way that our palms heat up when we quickly rub them together. There is one more similarity: when we rub the skin of one hand against the skin of the other, heat penetrates deep into the muscle tissue. So are microwaves: they work only in a relatively small surface layer of food, without penetrating deeper than 1-3 cm. Therefore, heating of food occurs due to two physical mechanisms— heating the surface layer by microwaves and subsequent penetration of heat into the depth of the product due to thermal conductivity.

This immediately follows a recommendation: if you need to cook, for example, a large piece of meat in the microwave, it is better not to turn on the oven at full power, but to work at medium power, but increase the time the piece remains in the oven. Then the heat from the outer layer will have time to penetrate deep into the meat and cook the inside of the piece well, and the outside of the piece will not burn.

For the same reasons, it is better to stir liquid foods, such as soups, periodically, removing the pan from the oven from time to time. This will help the heat penetrate deep into the soup container.

I would like to note that the radiation frequency in some industrial microwave ovens (the so-called variable frequency microwave, VFM) may vary and may not be 2450 MHz

Microwave oven device

Main components of magnetron microwave oven:

— a metal chamber with a metallized door (in which ultrahigh-frequency (microwave) radiation is concentrated), where the heated products are placed;
— transformer - source of high-voltage power supply for the magnetron;
— control and switching circuits;
- direct microwave emitter - magnetron;
— a waveguide for transmitting radiation from the magnetron to the camera;

Auxiliary elements:

— rotating table - necessary for uniform heating of the product from all sides;
— circuits and circuits that provide control (timer) and safety (mode locking) of the device;
- a fan that cools the magnetron and ventilates the chamber.

Harm from a microwave oven

Actually, this is a broad question, but everyone should have their own opinion on this matter. I found a bunch of information on the Internet, both “Pros” and “Cons” of using microwave ovens. But personally, I am still inclined to believe that a microwave oven is no more dangerous, and perhaps less dangerous, than a CRT TV. Therefore, I didn’t decide to write another hundred lines. At the end of the article, you can read a couple more lines on this topic in “Myths about Microwave Ovens.”

The only thing I noticed, and that basically two “camps” of supporters and opponents agree, is that you can’t heat breast milk in a microwave oven and then feed it to a baby, because. to some extent the formula of this milk changes slightly.

By the way, on this occasion, I found a photo that shows the range of the harmful influence of a microwave oven. It shows how safe it is to have a microwave in the house.

Precautionary measures

— Microwave radiation cannot penetrate metal objects, so it is impossible to cook food in metal utensils. Metal utensils and metal utensils (spoons, forks) placed in the oven during the heating process can damage it.

— Liquids in hermetically sealed containers and whole bird eggs cannot be heated in a microwave oven - due to the strong evaporation of water, high pressure is created inside them and, as a result, they can explode. For the same reasons, it is undesirable to overheat sausage products covered with plastic film.

— When heating water in the microwave, you should also be careful - water can overheat, that is, heat above the boiling point. A superheated liquid can boil almost instantly from careless movement. This applies not only to distilled water, but also to any water that contains few suspended particles. The smoother and more uniform the inner surface of the water container, the higher the risk. If the vessel has a narrow neck, then there is a high probability that when it starts boiling, superheated water will spill out and burn your hands.

— It is undesirable to place dishes with a metal coating (“golden border”) in a microwave oven - even this thin layer of metal is strongly heated by eddy currents and this can destroy the dishes in the area of ​​the metal coating.

Now let's turn our attention to the microwave characteristics that you need to take into account when choosing a microwave oven.

Microwave types standard features, have additional ones - grill, convection, and many more additional modes and others technical solutions cooking.