How to choose a microwave oven (2018). How to choose a microwave oven? Which brand of microwave oven to choose
Microwave ovens (MW ovens) have long been the most common household appliance, with which you can quickly defrost food, reheat already cooked food or cook a dish according to original recipe, and even disinfect metal-free kitchen cleaning sponges and cloths.
The presence of a convenient, intuitive interface, as well as multi-level protection, allows even a child to cope with the management of such a complex and high-tech device as a microwave oven. Some dishes can be easily and quickly prepared using built-in programs. And possible malfunctions can be completely eliminated by doing.
The heating of products placed in the microwave chamber occurs due to the impact on them of a powerful electromagnetic radiation decimeter range. In household appliances, a frequency of 2450 MHz is used. Radio waves of such a high frequency penetrate deep into the products, and act on polar molecules (mostly water in products), forcing them to constantly shift and line up along the lines of force of the electromagnetic field.
Such movement raises the temperature of the products, and the heating goes not only from the outside, but also to the depth to which radio waves penetrate. In household microwave ovens, waves penetrate 2.5-3 cm deep, they heat the water, and that, in turn, the entire volume of products.
Magnetron device - the main component
2450 MHz radio waves are generated special device – magnetron, which is an electrovacuum 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 design is a rod cathode, inside of which there is a filament. The cathode serves to emit electrons. Powerful ring magnets are located along the ends of the magnetron, which creates a magnetic field inside the magnetron, which is 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 electric field high tension. The geometry of the resonator chambers and the anode voltage determine the generated frequency of the magnetron.
The energy is removed by means of a wire loop connected to the cathode and led out to the emitter-antenna. From the antenna, microwave radiation enters the waveguide, and from it into the microwave chamber. The standard output power of magnetrons used in domestic microwave ovens is 800 watts.
If less power is required for cooking, then 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 within a 10-second interval and turn it off for 5 seconds. In science it's called pulse width modulation.
The magnetron generates a large amount of heat during operation, so its case is placed in plate radiator, which during operation should always be blown by the 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 you need it
To protect the magnetron from overheating, as well as the grill, which some models of microwave ovens are equipped with, special devices are used, called thermal fuse or thermal relay. They are available in different temperature ratings indicated on their body.
The principle of operation of the thermostat is very simple. Its aluminum body is flanged to the place where the temperature needs to be controlled. This ensures reliable thermal contact. Inside the thermal fuse is a bimetallic plate that has settings for a certain temperature.
When the temperature threshold is exceeded, the plate bends and actuates the pusher, which opens the plates of the contact group. Microwave power is interrupted. After cooling, the geometry of the bimetallic plate is restored and the contacts are closed.
Purpose of microwave oven fans
The fan is the most important component of any microwave oven, without which its operation will be impossible. It performs a number of important functions:
- First, the fan blows main detail Microwave ovens - magnetron, ensuring its normal operation.
- Second, other components electronic circuit 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, in the chamber, the cooked products also emit 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, together with the heated water vapor, escapes through special ventilation openings.
In the microwave from one fan, which is located at rear wall housing and sucks in air from the 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 protection and locking system
Any microwave oven has inside a powerful radio-emitting device - a magnetron. Microwave radiation of such power can cause irreparable harm to human health and all living beings, so a number of protection measures must be taken.
The microwave has a fully shielded metal working chamber, which is additionally protected from the outside by a metal case that does not allow high-frequency radiation to penetrate outside.
The transparent glass in the door has a screen made of metal mesh with small cell, which does not let out the radiation of 2450 Hz, a wavelength of 12.2 cm, generated by the magnetron.
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 do optimal choice, you just need to understand the advantages and disadvantages of each type of such lamps.
Double switches in view of their features are widely used in the home. How to connect such switches correctly and what you need to know to prevent errors in this case can be read in.
Microwave door fits snugly into cabinet and it is very important that this gap retains its geometric dimensions. The distance between the metal case of the chamber and the special groove of the door should be equal to a quarter of the wavelength of microwave radiation: 12.2 cm/4=3.05 cm.
In this gap, a standing electromagnetic wave is formed, which has a zero amplitude value precisely at the place where the door touches the body, so the wave does not propagate outward. In such an elegant way, the issue of protection against microwave radiation is solved with the help of microwave waves themselves. This method of protection in science is called a microwave choke.
To prevent the microwave oven from turning on with an open chamber 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 positioned and configured so that they only operate when the oven chamber is closed.
Microswitches on the door are also often referred to as limit switches.
The control unit is the brain of the device
Any control unit microwave oven and it performs two main functions:
- Maintaining the set power of the microwave oven.
- Turn off the oven after the set operating time has elapsed.
On older models of electric furnaces, the control unit was represented by two electromechanical switches, one of which just set the power, and the other the time interval. 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 (button or touch).
- Cooking or defrosting food using special programs "hardwired" into the memory of the control unit. In this case, weight is taken into account, and the oven will select the required power itself.
- Signaling the end of the program by the selected soundtrack.
In addition, at modern models there are upper and lower grills, a convection function, which are also “managed” by the control unit.
The control unit has its own power supply, which ensures the operation of the unit in both standby and operating modes. An important component is a relay unit that switches on commands the power circuits of the magnetron and the grill, as well as the circuits of the fan, the built-in lamp and the convector. The control unit is connected by loops to the keyboard and display panel.
An entertaining video with a story about the principle of operation of microwave ovens
See how simply explains what makes this amazing device work.
If the question of how a microwave oven works comes to your mind, then it will not be difficult to answer it, because this device has been on the home appliance market for a long time and its characteristics have been studied up and down. The principle of operation of a microwave oven is based on the effect of microwaves on the product placed inside the device. Details about what a microwave oven and microwave are will be discussed below.
The operation of devices of this type is based on the transformation of the so-called electromagnetic microwave fields. A similar field is transformed in thermal energy and warms up the food in the chamber. The principle of operation of a microwave oven differs from other devices for cooking: ovens (both gas and electric, where heating occurs due to the elementary heating of the contact surface and the surrounding space in the chamber) and stoves.
The principle of operation of the microwave oven allows you to heat only the object itself, placed inside. Therefore, the process of heating food is quite fast. At one time, it was this advantage that allowed the microwave oven to gain popularity and confidently take a leading position in the market. kitchen appliances. To defrost or reheat a cooked dish, it was no longer necessary to expend extra energy (for heating the entire chamber). In a few minutes, the electric wave action raised the temperature to the required level. For example, a piece of frozen meat was ready for cutting and further cooking without a long wait.
Traditional types of thermal exposure work a little differently. Heat is supplied to the surface heated object, as a result of which quite often one can observe such a picture when outer side The defrosted dish has already crusted and started to burn, but inside it remains frozen. This is due to the fact that the heating occurs unevenly, the heat is distributed vertically: from the upper layer to the inner one. This method is much less efficient than the operation of a microwave oven, moreover, it requires certain skill and culinary skills from the owner, while cooking in a microwave oven is enough just press a couple of buttons and expect results.
The electrical circuit of the microwave oven has remained unchanged since the launch of the device in mass production. For the sake of current requirements, the appearance has changed, the devices have become more aesthetically attractive. A lot of hardware functions have been added, more comfortable methods of control, regulation of the power of exposure, but the principle itself has remained the same as 50 years ago. This is due not only to the well-known saying “why change what works so well”, but the principle itself does not imply any radical changes.
By the way, when it comes to microwave and microwave ovens, it should be remembered that these concepts are identical, these devices are not different types devices, as it may seem to someone at first glance.
A couple of decades ago, a microwave oven was a luxury item and was more likely to be present in the kitchen as an element of decor, rather than being a subject for everyday use. Of course, over time, manufacturing techniques became more accessible to the mass market, which led to the wide availability of microwaves and their ubiquity. So, from a luxury item and a rare technological curiosity, the microwave oven turned into indispensable assistant in the kitchen, able to prepare simple meals in a matter of moments.
A few words about heating
The microwave oven device includes the so-called. This definition should be familiar to anyone who knows how radar works and works.
microwave like mechanical device, is able to quickly heat food precisely thanks to the magnetron.
If we consider the electrical circuit of a microwave oven (for example, Samsung) from the inside, it becomes clear that these developments have migrated to the segment of household appliances from heavy industry. Different kinds devices differ only externally. So, for example, the LG microwave circuit will not differ much from the Daewoo brand microwave circuit.
This is how a microwave oven works: the magnetron begins to release energy during operation, which is converted into heat and used as targeted heating. This type of device is powered by an anode-filament stabilizer transformer. At first, this particular part was the most expensive in the production of microwaves. But over time, its cost fell to an acceptable level, which made it possible to mass-produce devices.
Considering internal organization microwave, it is worth considering the design in more detail shunt magnetic circuit. This unit allows you to change the voltage increase within an error of 2% within a 10% power grid fluctuation. Main Feature The transformer is a high-strength inductive leakage magnetic core. It may be that in words the description of the principle of operation of a microwave oven looks somewhat complicated, but in practice the device is quite simple.
At the time of the start of the design, design engineers were faced with increased level noise during microwave operation. In general, it is worth mentioning that high level Noise is a problem with many devices based on a heat dissipation or cooling unit. Subsequently, this problem, of course, was solved, and rather interesting way. To eliminate increased vibration, some parts began to be connected by welding.
The microwave device begins first of all with the case. In most cases, it is box rectangular shape . This was done not because designers suffer from a lack of imagination, the point here is in the specifics of operation.
When the microwave is turned on, the waves are not only directed towards the object being heated, they are also reflected from interior decoration housing, which significantly increases the thermal effect.
Also, the rotating part - the saucer - allows you to optimize the heating process. As it rotates, the waves are distributed evenly over the entire surface of the heated object. A wave entering a tank with products always has different shape - this is another specific feature microwave ovens. Some waves are nodal, others are formed in the form of beams, so the impact is chaotic in nature, but optimization measures make it possible to level this process.
Throughout the history of the existence of this type of device, the process of their manufacture, thermal exposure and its optimization have been perfected by manufacturers to an ideal state. To date, a microwave oven is a complete device, completely ready for use, reliable and safe, which is confirmed by many certificates from international monitoring consortiums that regulate the harmful effects of technology on the human body.
An important function of the microwave oven door
No less attention during production is given to the door. In microwave ovens, the door is not only decorative element, but also serves as a kind of fuse. The principle is very simple: if you open the door, the lock is activated and the operation of the units stops. Despite the apparent simplicity, the device of the door is quite difficult, because it is connected with safe operation the entire apparatus.
So, let's take a closer look at how the microwave oven door works:
- Firstly, the manufacturer needs to ensure that the door and body of the device fit perfectly with each other with a minimum angle. Large gaps prevent the device from being used. The reason is simple, the door serves a kind shield from microwave radiation , and if the gap is large enough, the radiation may penetrate outside the cooking chamber. It has long been known what radiation is and what its danger is.
- Secondly, the perimeter of the door is equipped with a high frequency throttle. This device serves to reduce radiation to an acceptable level.
- Thirdly, at the time of casting the door body, a lot of additives are added, with the help of which a high percentage of radiation absorption is achieved. Of course, one cannot be completely sure of 100% absorption of radiation, but there is no doubt that the residual waves do not pose a danger and significant harm to human health.
In the entire history of the existence of the device, this part of the microwave has not undergone any major changes. In general, it is always two handles, one of which is responsible for the temperature, and the other for the cooking time. Of course, today you can find many differences in modifications: from simple "wheels" to control units, which will have many different functions. That's just the essence of them, often comes down to an old and proven principle, nothing new in the device microwave ovens for all the time of their existence is not invented. The fundamental difference can only be in the concept of controlling the device.
Now many manufacturers (for example, Samsung) are betting on the innovative component and integrating touch control panels into their microwave ovens.
A little about the dangers of microwaves
Disputes about do not subside from the moment they are launched into mass production. To date, there is no reliable information confirming the harm from using this type of device.
Do not forget that the microwave does not emit radioactive waves. On the contrary, the microwave oven allows you to cook food without losing it. useful properties. Food is healthier because it retains up to 80% of vitamins and minerals.
Traditional ovens and stoves cannot boast of such a result. If you operate the device clearly according to the rules, then there is no danger from its operation. This conclusion is also confirmed by the way the microwave oven is arranged, as mentioned above.
Unhealthy food cooked in a microwave oven (the so-called fast food) can bring harm, and thermal microwave exposure has nothing to do with it. The harm of pies (and other flour products) lies not in the fact that they are cooked in the oven, but in their high calorie content and slow absorption by the body.
The frequency of your microwave, which is also mentioned when it comes to harm, also does not play any significant role. It (frequency) can change as much as you like, but this (contrary to popular belief) will not lead to an increase or decrease in radiation, the background remains the same.
Conclusion
The conclusion that suggests itself: a microwave oven is a very simple, but at the same time indispensable device in the kitchen, which makes our life easier every day. It is convenient and unpretentious in use and maintenance, easy to clean, takes up little space and consumes very little energy. The microwave device, as discussed above, remained unchanged: a magnetron, an I/O transformer, an I/O capacitor, a cooler, and a cooking chamber. The reliability of this technique has been proven in practice for several decades.
If earlier microwave ovens were used only for heating food, then modern models provide wide opportunities for complete cooking. As multifunctional devices, they boil, fry and bake, and do it faster than traditional kitchen appliances.
The principle of operation of the microwave oven
Heating of food in the microwave occurs under the influence of microwave frequencies. They act on the liquid molecules that are present in every product. Under the influence of electromagnetic oscillations, water molecules begin to move faster, colliding with each other. This raises the temperature of the food and heats up the food quickly (up to a maximum of 100°C).Low Maximum temperature does not allow you to achieve a golden crust when cooking meat and baking, however, manufacturers have found a way out by equipping modern microwave ovens with grills. This option allowed microwave ovens to catch up in functionality with ovens, ahead of them in cooking speed, however, the price of such devices has become higher.
Despite the convenience and efficiency of microwaves, many users are in no hurry to acquire this useful tool doubting its safety. In fact, microwave ovens are harmless to humans. This is facilitated by several degrees of protection:
- tight fit of the door;
- a screen with a protective grid that captures electromagnetic waves;
- blocking the door of the operating device or automatically turning off the oven when opened.
The uniqueness of microwave devices
The main advantage of microwave ovens over other kitchen appliances is speed. According to this parameter, modern pressure cookers can compete with them, in which products are cooked under pressure. However, microwaves have an undeniable “plus”: they can be opened during operation, while cooking under high pressure implies tightness.The difference in speed is explained by the fact that ultra-high frequencies instantly penetrate inside to a depth of up to 5 cm and simultaneously heat up all the water molecules, and hence the entire product. When heated by fire or electricity, the molecules of the outer shells are first dispersed, while the heating of the inner layers occurs later.
In addition to speed, microwave ovens have the following advantages over traditional kitchen appliances:
- compact dimensions;
- ease of care;
- lack of smells of the prepared products;
- high efficiency: energy is spent on heating food, not the surrounding space;
- preservation of vitamins in foods.
Selection Options
Volume
The dimensions of the chamber are calculated based on the number of family members and the desired functionality, the higher these parameters, the higher the cost of the microwave.
- The unit with a volume of 12-15 liters is optimal for 1 person. You can heat sandwiches, bake potatoes or defrost food in it.
- The oven with a capacity of 16-20 liters is sufficient for 2 people. There you can cook soup in a small pot or bake chicken.
- Apparatuses from 20 to 30 l are designed for an average family of 3-4 people and cooking the most different dishes: from borscht to pies.
- A device with a volume of more than 30 liters is able to satisfy the appetites of 5-6 eaters. A goose or a turkey can fit entirely in such a chamber, you can bake cake layers in it and cook a large number of soups and side dishes at a time. But remember that such a microwave oven will cost many times more than models for 1-2 people.
Design features
The design and price of a microwave oven largely depend on its size and functionality. The more “advanced” the model is, the larger its pallet will be, and the control system will be more convenient and pleasant.When choosing a microwave device, pay attention to the following points.
Pallet diameter. Depending on the volume of the chamber, the pallet can be small or large. Non-standard pallet with original form finding a seat for sale is quite difficult. The most popular are pallets with a diameter of 245-270 mm and a seat in the form of a cross or shamrock.
Door opening type. Both a button and a handle can be provided to open the device. Both options are equally reliable: the user can only choose the method that is convenient for him personally.
Control method. There are 3 types of control: mechanical (rotary), clock and touch. The first option is cheaper, it is the simplest and most reliable: power and time are set using round knobs. The disadvantage of this method is the impossibility of setting the exact time to the second. The push-button and touch mechanisms have a display on which you can program the time and method of cooking. Touchpads are more hygienic, but sometimes less reliable than pushbuttons.
All microwave ovens are divided into 2 categories: built-in and freestanding. The first type is best for small kitchens, however, its price is higher. Separately standing devices more affordable, but take a lot kitchen space, therefore, before buying, it is advisable to think in advance about where the new acquisition will stand.
Power
The maximum power of microwave ovens can range from 450 to 1700 watts. The larger the device, the more power it needs, and the faster the dishes will be cooked, which is why the price of such microwaves is usually higher. A large number of the electricity spent on this is compensated by a decrease in the time of its consumption, so it is not known whether it will be possible to save money by buying a low-power device.During the cooking process, the power, and hence the amount of energy consumed, can be adjusted. There is an opinion that when baking meat in the microwave, it turns out to be tougher than with traditional cooking. This only happens if you only set the cooking time. The default is maximum power, because of which the dish acquires excessive rigidity.
When using a microwave oven for each product, you need to set your own cooking parameters:
- 100% power is best set for quick warm-up;
- 70% for roasting meat and poultry;
- 50-60% for the preparation of fish and semi-finished products;
- 20-30% for brewing herbs;
- 10% for dough proofing.
Functions
The functions of the simplest cheap microwave ovens include simple heating and defrosting of food. More advanced models allow you to cook recipes. This is convenient, instead of remembering the optimal power and cooking time for a dish, just press the button with the name of the dish and indicate its weight. In some ovens, you can not only use the standard modes, but also program your favorite recipes.
If you want to make complex culinary masterpieces and do not plan to save on purchases, you can purchase equipment with a number of additional functions.
Double emission. Appliances with this function allow you to heat food more evenly, while consuming less energy.
. With it, you can get a golden crust on meat or bread, make toast or fry sausages. The grill can be quartz or heating element. The first option is more expensive, but it is economical, quick and easy to maintain. Teng takes more space in the oven chamber, but the user can change its location, achieving maximum heating of the products in the right place.
. Devices with this function are equipped with a fan that provides continuous circulation of air heated up to 240-250 ºС. Thus, the food receives uniform heating, and an appetizing crust forms on its surface. In the absence of an oven in the kitchen, a convection microwave can be a good way out. Sometimes such devices are also equipped with a grill, so that users can choose the best combination of three modes for themselves. Convection devices have 2 disadvantages: high price and high power consumption.
Removing odors. Devices with an odor removal function are good for intensive use of ovens. In them, you can alternately cook foods with sharp flavors and not be afraid that sweet pies will smell like meat or garlic.
Automatic weighing. In order not to set the weight of the products every time, you can purchase a design with built-in digital scales. The oven itself will determine the weight and cook the dish in accordance with this parameter.
In addition to these features, manufacturers are building bread makers, steamers, and toasters into microwave ovens. Many models are equipped with additional useful devices: so, on a metal “Krusty plate” you can fry foods like in a pan, and a multi-level grill will allow you to simultaneously heat up food in several plates at once; automatic heating will allow you not to remember the required power and time for each product, the system will determine these parameters automatically.
It is worth remembering that multifunctional units are not only more expensive, but also quite bulky and volumetric structures, so they are unlikely to be appropriate in small kitchens.
Camera inner lining
The ease of maintenance and the service life of the entire structure depend on what material the camera is covered with.Enamel. The enamel layer is typical for simple and cheap models. He just washes, but does not stand too much high temperatures.
Stainless steel . The coating is able to withstand any temperature and operating conditions, but it is quite difficult to clean it from contamination.
(antibacterial coating). Chambers trimmed with similar materials durable, resistant to thermal effects, they are easy to clean, but the cost of such furnaces is quite high. The bioceramic coating is quite fragile and may break if handled carelessly.
Thus, if the microwave oven is used only for heating sandwiches and defrosting, the enamelled coating of the chamber is sufficient. But the chambers of ovens purchased as the main kitchen appliances must be covered with steel or bioceramics.
The cost of microwave ovens
Prices for different models of microwave ovens can vary greatly. The cost depends not so much on the popularity of the brand, but on the characteristics of the equipment. So, a simple mechanically controlled device with a volume of 15-20 liters can be bought for
The main part in any microwave oven is the magnetron. A magnetron is such a special vacuum lamp that creates microwave radiation. Microwave radiation has a very interesting effect on ordinary water, which is contained in any food.
When irradiated with electromagnetic waves with a frequency of 2.45 GHz, water molecules begin to oscillate. As a result of these vibrations, friction occurs. Yes, the usual friction between molecules. Heat is generated due to friction. It warms up the food from the inside. This is how a microwave oven works in a nutshell.
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 the radiation from escaping. For uniform heating of food, a rotating table is installed inside the chamber, which is driven by a motor-reducer (motor), which is abbreviated as 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 drives cold air through the magnetron. Further, the heated air from the magnetron through the air duct is sent to the chamber and is also used to heat food. Through special non-radiating holes, part of the heated air and water vapor is removed to the outside.
In some models of microwave ovens, a dissector is used to form uniform heating of food, which is installed at the top of the microwave chamber. 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.
Electric circuit of the microwave oven.
Let's take a look at the simplified wiring diagram ordinary 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, a display, a button or touch panel, electromagnetic relays, and a buzzer. These are the brains of the microwave. In the diagram, all this is depicted by 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 through buffer elements (transistors) controls electromagnetic relays: RELAY1, RELAY2, RELAY3. They turn on / off the actuating elements of the microwave oven in accordance with the specified operation algorithm.
Actuators and circuits are a magnetron (Magnetron), a motor-reducer of a table T.T.Motor (Turntable motor), a cooling fan F.M ( fan motor), grill heater ( Grill Heater), backlight O.L ( Oven Lamp).
We especially note the executive circuit, which is a generator of microwave radiation.
This circuit begins with a high voltage transformer ( H.V. Transformer ). He is the healthiest in the microwave. Actually, this is not surprising, because through it you need to pump power of 1500 - 2000 W (1.5 - 2 kW), necessary for the magnetron. The output (useful) power of the magnetron is 500 - 850 watts.
AC voltage 220V is supplied to the primary winding of the transformer. An alternating voltage of 3.15V is removed from one of the secondary windings. It is fed 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.
Other secondary winding high-voltage transformer, as well as a voltage doubling circuit on a 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 is somewhere around 300 mA (0.3A).
As a result, the electrons emitted by the filament winding begin their movement in vacuum.
The special trajectory of the movement 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.
Here is such a 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, there are many protective elements in the microwave oven circuit (see KSD thermal switches and analogues.). So, for example, a thermal switch controls the temperature of the magnetron. Its nominal temperature during operation is somewhere around 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 signed on the diagram as OVEN THERMAL CUT-OUT(installed on the air duct), GRILL THERMAL CUT-OUT(controls grill temperature).
In the presence of an emergency situation and overheating of the magnetron, 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 С.
Very important elements of the microwave oven are three switches that are built into the right end of the microwave oven chamber. When the front door is closed, the two switches close their contacts ( PRIMARY SWITCH- main switch, SECONDARY SWITCH- secondary switch). The third - MONITOR SWITCH(control switch) - opens its contacts when the door is closed.
Failure of any of these switches will render the microwave inoperable and blow the fuse (Fuse).
To reduce the interference that enters the power grid when the microwave oven is running, there is a power filter - NOISE FILTER.
Microwave accessories.
In addition to the basic structural elements, a microwave oven can be equipped with a grill and a convector. The grill can be made in the form heating element(TEN "a) or infrared quartz lamps. These microwave oven elements are very reliable and rarely fail.
Grill heating elements: metal-ceramic (left) and infrared (right).
The infrared heater consists of 2 infrared heaters connected in series. quartz lamps at 115V (500 - 600W).
Unlike microwave heating, which occurs from the inside, the grill creates radiant heat that heats food from the outside in. The grill heats food more slowly, but without it it is impossible to cook fried chicken.
A convector is nothing more than a fan inside the chamber, which works in tandem with a heater (heater). The rotation of the fan circulates 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 must be considered when repairing a microwave oven.
For those who wish to understand in more detail the structure of microwave ovens, an archive has been prepared with service instructions microwave ovens (Daewoo, SANYO, Samsung, LG). The instructions provide circuit diagrams, disassembly diagrams, recommendations for checking elements, a list of components.
The working principle of a microwave oven: 6 main elements
Thanks to the microwave oven, you can easily and quickly heat up any dish. Microwave oven (MW) is currently very popular, it is the most popular kitchen appliance. With the help of a microwave oven, you can not only heat or cook food, but also defrost food and even disinfect some kitchen utensils containing no metal. This device has become quite commonplace today.
Microwave device: basic structural elements
The microwave oven is a household electrical appliance, which is intended mainly for cooking or heating food in fast mode. Microwaves are also used in some industries where you need to heat the necessary materials.
Microwave despite small size, consists of many parts
Unlike conventional ovens, heating different foods in this device happens quite quickly, since radio waves are able to penetrate deep into the products. This drastically reduces the heating of any product and helps to preserve all the useful substances in it.
The device of all microwave ovens consists, as a rule, of the same components. The design of microwave ovens has the 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.
The structure of the microwave oven:
- Camera equipped with a rotating podium;
- Magnetron, is the main element - a microwave emitter;
- Transformer;
- Metal case with a door that is blocked when the device is in operation;
- Scheme of management and communications;
- Waveguide.
Also inside the microwave oven must be equipped with a fan. Its purpose is very large, since without it the device itself will not work. Such a device ensures excellent operation of the magnetron and cools the electronic circuits.
How a microwave oven works: its varieties
The operation of a microwave oven is very simple, it is based on microwave radiation. The heart of every microwave oven is an element such as a magnetron. He is the source of radiation. The frequency of microwaves is approximately 2450 MHz, and the power of modern microwaves can be 700 - 1000 watts. This oven is powered by electricity.
The microwave oven heats the dish evenly from all sides
In order for the magnetron to work well and not overheat, a fan is installed next to it. It also circulates air inside the oven itself and contributes to 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 the products, makes their molecules move very quickly. These actions contribute to friction, as a result of which heat is released (there is physics). This is warm and will reheat food.
Types of electrical appliances:
- With grill;
- Convection oven;
- Inverter controlled device;
- An appliance with microwaves that are distributed evenly;
- Mini microwave.
The main advantage of all microwaves is the design. The market provides a huge selection of devices, you can choose both a stylish and ergonomic model. The description of these models will allow you to choose the model you like, which will become not just a decoration of the kitchen, but also its highlight. An example would be a Samsung microwave oven.
Control unit: the principle of operation of the microwave
Every microwave has one important element like a control unit. It, in turn, performs two main functions: it maintains the set power and turns off the device when the set time has elapsed. To date, technology has developed the new kind this element is electronic.
Today, the 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, it is also controlled by a control unit.
Among the advantages of a microwave oven, it is worth noting the low price and long service life.
For today, command block equipped with different microprocessors, which, in turn, support the functionality of other programs. Therefore, the power supply may be responsible for the operation of additional functions.
Additional service functions:
- Built-in clock;
- Power indicator;
- Automatic defrosting;
- A sound signal that indicates the completed operation.
The electronic unit is closely connected with the display panel and keyboard. The most important detail such a block is a relay block. He is responsible for the operation of the fan, convector, built-in lamp and even the magnetron.
Microwave frequency: magnetron and its components
The principle of operation of the microwave oven is that the magnetron, when the microwave oven is turned on, begins to release energy, and then it is converted into heat. This is heat is coming for heating food. Magnetron is translated as an electrovacuum diode, which consists of a copper anode. This is the most expensive part of the furnace.
The heating of food that is inside the microwave occurs under the influence of electromagnetic radiation, that is, microwave radio waves. Due to the fact that radio waves penetrate deep into the heated product, it is heated very quickly and efficiently.
If the magnetron breaks down, then without the appropriate experience it is quite difficult to fix it yourself
Magnetron decoding is a device that produces great amount heat, due to the frequency of radiation. The radiation frequency is 2.4 GHz. Coefficient useful action(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 is made of copper;
- In the center is a cathode with a filament;
- The end parts are occupied by magnets, they create the magnetic field necessary for radiation;
- Leaded to the antenna, which radiates energy, a wire loop.
With the help of the antenna-emitter, the energy first enters the waveguide, and then into the furnace chamber. The voltage supplied to the anode is 4 thousand watts, the filament is 3 thousand watts. 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 overheating it.
The device and principle of operation of the microwave oven (video)
From English, such a statement Microwave oven can be deciphered as a microwave oven. This design represents household appliance, which is powered by electricity and differs in that it defrosts or reheats food very quickly. This happens due to microwave radiation.