microwave ovens or so-called microwaves have become devices that are located in the kitchen of almost every person. With their help, you can easily heat the already cooked products, or defrost them. Some craftsmen have learned to cook in a microwave oven a huge number of dishes or to disinfect a sponge or cloth. If you are interested in the principle of operation and the device of the microwave oven, then we will try to answer it in this article.
In order to make it convenient for the user to control the device, an intuitive interface has been included in its design, which is equipped with a child protection system and quick-cooking programs. In case of any faults, you can, in most cases, fix them yourself.
The principle of operation of the
microwave oven In order to heat up the food, you need to place the dishes with the products in the microwave oven and select the program, if fast heating is used, you need to set the time. Products are heated by exposure to powerful electromagnetic radiation. The frequency of the microwave, which is installed in the kitchen, is 2450 MHz. How does food heat occur: High-frequency waves penetrate deep into products and begin to affect polar molecules( most often water), leading them to cyclical motion along the lines of force of electromagnetic fields.
Thanks to the application of this method, food is heated not only outside, but also inside the food. In most models used in the kitchen, this figure ranges from 2.5 to 3 centimeters.
How are these waves generated?
A special device called a magnetron, which is an electrovacuum diode consisting of a large cylindrical anode made of copper, which combines 10 wall sectors, is used to generate radio waves of this frequency, and they are also made of copper.
At the center of the device is a core cathode with a thread inside the channel. The cathode is designed for the emission of electrodes. In order for the unit to generate microwave radiation, it is necessary to create a magnetic field in the cavity of the magnetron. To do this, use powerful ring magnets, which are located on the ends of the part.
To create an emission, it is necessary to apply four thousand volts to the anode, and only three to the channel filament.
For the removal of energy, the structure of the device provides wire loops that are connected to the cathode, and that in turn is brought into the so-called "radiant antenna".From this device, the generated radiation goes directly into the waveguide, which distributes it throughout the main chamber. Often the standard power of this element, which is installed in most models of microwaves, is about 810 watts.
If less power is needed for heating or cooking, the magnetron simply cycles on and off.
In science, this phenomenon is called pulse-width modulation. In order for the device to produce 400 W, namely half of its output power during a 20-second interval, it is necessary to de-energize the magnetron for 10 seconds and then supply electricity for the same 10 seconds.
The device generates a large amount of heat during operation, so to cool it, the element is installed in a plate radiator, so that it is constantly blown by the air flow, thanks to a small cooler built into the microwave. In case of overheating, this structural element can simply simply fail, therefore it is equipped with a protective device, namely a thermal fuse.
Purpose of the
thermal fuse In order to protect the magnetron and the grill, which is installed in some models of microwaves, from overheating, the installation includes a thermal switch, or as they are also called thermal fuses. They are separated according to their ability to withstand different amounts of heat, in order to find out what kind of heat you have, you need to find a sticker on the device case with information or look in the technical data sheet of the device.
In fact, the device is quite simple in principle understanding its operation. The body of the product is made of aluminum alloy. The device is fastened by means of a flange connection, which is able to ensure a tight fit with the area where the temperature will be measured directly. Inside the case is a bimetallic plate, which is made with the expectation of resistance to certain temperatures.
In case of exceeding a predetermined threshold, the plate is simply compressed and thereby actuates the pusher, which is designed to open the contact group. The power supply is interrupted and the furnace stops functioning. Gradually cooling down, the plate returns to its original shape and re-closes the contacts.
Purpose of the cooler in the microwave oven
The cooler is one of the most important components of the microwave oven, without it there will be full operation of the device. Thanks to it, the following functional tasks are carried out:
- Cooling the magnetron to ensure its proper operation.
- Cooling of other system components that can also generate heat, such as electronic circuits.
- Some models of microwaves are equipped with a grill function and install a cooler for cooling the thermal switch.
- To create excess pressure in the cavity where food is placed. Due to this, air and vapor are removed, which are removed through specialized ventilation ducts.
In microwave ovens, cooling is carried out with the help of a single fan, which distributes the air through the chamber with the help of special air vents that direct air to the parts to cool them.
How to protect against microwave radiation
Since the magnetron emits strong electromagnetic radiation that can harm the human body and pets, a multi-level protection system is used in the device.
The working chamber of the device is enameled to block the radiation, and from above it is covered with a metal casing, which completely stops its exit to the outside.
To protect the glass window in the door of the device, use a grid with small cells, which is made of steel, and it blocks radiation up to 2450 Hz, with waves up to 12 cm.
The door must fit well to the body and have no gaps. In the case when the gap between them increases, you need to check the loop and return it to its original state.
Permanent electromagnetic waves can form between them, which are located directly at the point of contact between the door and the device case, and have a zero amplitude value, which is why the emitted waves cannot propagate outside the case. This method in science was named as “microwave choke”.
The device is protected from switching on with an open chamber a system of microswitches that control and fix the position of the door in it. Most often, the device is provided from three similar switches:
- Switching magnetron.
- Control backlight bulb.
- A switch that controls the position of the door and informs the control unit about its position.
The control unit of the device
The control unit is installed in each device produced at the moment, it provides the implementation of two functions:
- Maintaining the specified power of the device.
- Turns off the device after performing the specified operation.
In older models, the device is made of two electromechanical switches, which were responsible for the above functions. Over time, technology has evolved and electric control units have been invented. At the moment, microprocessors are installed in the devices, which can be equipped with additional programs to simplify use, with some functions: automatic defrosting of food and preparation of certain dishes, built-in clock, indicators showing the power, sound signals about the completion of the process.
The command control panel is equipped with a personal power supply that feeds it offline during the operation of the microwave.
Conclusion
In this article, we reviewed the principle of operation and the device of a microwave oven, familiarized with its internal component and the possible use of the device in the home space. Undoubtedly, it can make life easier for anyone in the kitchen and save a lot of time.
