From 65438 to 0946, Spencer was a researcher at Raytheon Company in the United States. By chance, he found that the microwave oven melted the candy. Facts have proved that microwave radiation can cause molecular vibration inside food, thus generating heat. 1947, the first microwave oven came out.
As the name implies, microwave ovens use microwaves to cook and cook. Microwave is an electromagnetic wave. The energy of this electromagnetic wave is not only much larger than that of ordinary radio waves, but also has "personality". As soon as the microwave touches the metal, it will reflect, and the metal can't absorb it or conduct it at all. Microwave can pass through insulating materials such as glass, ceramics and plastics, but it will not consume energy. For food containing water, microwave cannot penetrate, but its energy will be absorbed.
Microwave ovens are made by using these characteristics of microwaves. The shell of the microwave oven is made of metal materials such as stainless steel, which can prevent the microwave from escaping from the oven, so as not to affect people's health. Food containers are made of insulating materials. The heart of microwave oven is magnetron. This electron tube, called magnetron, is a microwave generator, which can generate microwaves with a vibration frequency of 2.45 billion times per second. This invisible microwave can penetrate the food to a depth of 5 cm and make the water molecules in the food move with it. Intense exercise produces a lot of heat energy, so the food is cooked. This is the principle of microwave heating. When cooking food with an ordinary stove, heat always gradually enters the food from the outside. When cooking in a microwave oven, the heat directly enters the food, so the cooking speed is 4 to 10 times faster than other stoves, and the thermal efficiency is as high as 80%. At present, the thermal efficiency of other stoves cannot be compared with it.
Because of the short cooking time, microwave oven can keep the vitamins and natural flavor of food well. For example, cooking green peas in a microwave oven can almost keep vitamin C from losing at all. In addition, microwave can also be used for disinfection and sterilization.
When using the microwave oven, be careful not to "burn" in the air, because the energy of the microwave cannot be absorbed when "burning" in the air, which is easy to damage the magnetron. In addition, human tissues contain a lot of water, so it is necessary to open the oven door to extract food after the magnetron stops working.
Basic structure of microwave oven
Basic shape and structure of microwave oven
(1) Safety interlock switch of oven door-ensure that the microwave oven can't work when the oven door is open and can work when the oven door is closed;
(2) Video window-a metal shielding layer, which can observe the cooking situation of food through the grid;
(3) Ventilation-ensure good ventilation during cooking;
(4) turntable support-driving the glass turntable to rotate;
(5) Glass turntable-the container for holding food is placed on the turntable, and the turntable rotates when heated, so that the food is cooked evenly;
⑥ Control panel-controls the cooking of each gear;
All landowners oven door switch-press this switch, the oven door opens.
principle of operation
(1) furnace. The furnace cavity is a microwave resonant cavity, which is a space for converting microwave energy into heat energy to heat food. In order to even the food in the heating furnace cavity, there is a special device in the cavity of the microwave oven. The original microwave oven was equipped with a metal fan at the top of the oven cavity, that is, a microwave agitator, to interfere with the propagation of microwaves in the oven cavity, thus making food heating more uniform. At present, a glass turntable driven by a micro-motor is installed at the bottom of the cavity of a microwave oven, and the heated food is placed on the turntable and rotates around the motor shaft together with the turntable, so that it moves relative to the high-frequency electromagnetic field in the oven, thus achieving the purpose of homogenizing the food in the heating furnace. Domestic original automatic lifting turntable, more uniform heating, better cooking effect.
(2) oven door: the oven door is the entrance and exit of food and an important part of the microwave oven cavity. The requirement is very high, that is, the food heating in the furnace cavity can be observed from the outside, and the microwave cannot be leaked. The oven door consists of a metal frame and a glass observation window. There is a metal microporous net in the glass interlayer of the observation window, which can not only see food through it, but also prevent microwave leakage. Because the mesh size of the metal mesh in the glass interlayer is precisely calculated, it can completely block the penetration of microwave.
In order to prevent microwave leakage, the switch system of microwave oven is composed of several safety interlock microswitch devices. If the oven door is not closed properly, the microwave oven won't work. If the microwave oven doesn't work, there will be no microwave leakage.
In order to prevent the microwave from leaking from the gap between the oven door and the oven cavity after the oven door is closed, an anti-flow groove structure is installed around the oven door of the microwave oven, or a door seal made of silicone rubber can absorb a small amount of microwave that may leak. The backflow preventer is a special-shaped groove structure arranged on the door, which has the function of guiding microwave inversion. At the entrance of the surge tank, the microwave will be cancelled by its backward reflection wave, so that the microwave will not leak.
Because the door seal is easy to be damaged or aged, the leakage-proof effect is reduced. Therefore, most microwave ovens now adopt the structure of anti-chute to prevent microwave leakage, and rarely use silicone rubber door seals. According to the principle of microwave radiation, the chute structure is a stable and feasible method to prevent microwave leakage. Galanz microwave oven produced by Guangdong Galanz Enterprise (Group) Co., Ltd. adopts the world's most advanced structure and production technology of anti-leakage tank, and its multiple anti-microwave leakage technologies make the microwave leakage control technology reach the international advanced level.
(3) Electrical circuit: The electrical circuit is divided into three parts: high-voltage circuit, control circuit and low-voltage circuit.
(a) High-voltage circuit: The circuit behind the secondary winding of high-voltage transformer is a high-voltage circuit, which mainly includes magnetron, high-voltage capacitor, high-voltage transformer and high-voltage diode.
(2) Magnetron: Magnetron is the heart of microwave oven, from which microwave energy is generated and emitted. Magnetron needs a high pulsating DC anode voltage and a cathode voltage of about 3 ~ 4 V when it works. A voltage doubler rectifier circuit consisting of a high voltage transformer, a high voltage capacitor and a high voltage diode provides the magnetron with a working voltage that meets the above requirements.
(c) Low-voltage circuit: The circuit between the primary winding of the high-voltage transformer and the power inlet of the microwave oven is a low-voltage circuit, including the control circuit. It mainly includes fuse, thermal circuit breaker protection switch, interlocking microswitch, lighting lamp, timer and power distribution switch, turntable motor, fan motor, etc.
(4) timer. Microwave ovens generally have two timing methods, mechanical timing and computer timing. The basic function is to select and set working hours. After the set time, the timer automatically cuts off the main circuit of the microwave oven.
(5) Power distributor. The power distributor is used to adjust the average working time of the magnetron (that is, the ratio of "on" and "off" time when the magnetron works intermittently), thus adjusting the average output power of the microwave oven. Generally, the mechanical control type has 3 ~ 6 calibration files, and the computer-controlled microwave oven can have 10 adjustment files.
(6) Interlocking microswitch. Interlocking microswitch is an important safety device of microwave oven. It has multiple interlocking functions, all controlled by oven door opening button or oven door handle. When the oven door is not closed or opened correctly, disconnect the circuit to stop the microwave oven.
(7) Thermal circuit breaker. Thermal circuit breaker is an element used to monitor the working temperature of magnetron or furnace cavity. When the working temperature exceeds a certain limit, the thermal circuit breaker will immediately cut off the power supply and stop the microwave oven.
Taboos in use and maintenance
(1) The microwave oven should be placed in a ventilated place, and there should be no magnetic substances nearby, so as not to interfere with the uniform state of the magnetic field in the furnace cavity and reduce the working efficiency. Keep a certain distance from TV and radio, otherwise it will affect the visual and auditory effects.
[2] When cooking food, don't put it in the oven and don't work with electricity. Don't let the microwave oven run with no load, or it will damage the magnetron. In order to prevent careless no-load operation, a glass filled with water can be built in the furnace cavity.
[3] All heat-resistant containers such as metal tableware, bamboo, plastic and lacquerware, and concave-convex glass products are not suitable for use in microwave ovens. Porcelain dishes can't be inlaid with honeysuckle. Containers for food must be placed in special plates for microwave ovens, not directly in the oven cavity.
[4] The heating time of microwave oven depends on the material and dosage, and it is also related to the freshness and water content of food. Because the heating time of various foods is different, it should be shorter when the heating time required for food is uncertain, and the heating time can be increased according to the raw and cooked degree of food after heating. Otherwise, if the time is too long, the food will harden and lose its fragrance, color and taste. Adjust the timing and power (temperature) knob according to the food type and cooking requirements, so that you can read the instructions carefully and understand them.
[5] Eggs with shells and sealed food cannot be cooked directly. In case of explosion.
[6] Ensure that the oven door is closed, and ensure that the interlock switch and safety switch are closed. After the microwave oven is turned off, it is not appropriate to take out the food immediately, so there is still residual heat in the oven and the food can continue to cook. /kloc-it's better to take it out after 0/minute.
7] The furnace should always be kept clean. After disconnecting the power supply, wipe it with a damp cloth and neutral detergent. Do not rinse or let water flow into the electric appliances in the furnace.
(8) Check the oven door and door lock regularly. If it is damaged or poorly closed, please stop using it to prevent microwave leakage. It is not advisable to put your face near the observation window of the microwave oven, so as not to hurt your eyes by microwave radiation. It is also inappropriate to be exposed to microwaves for a long time, so as not to cause dizziness, dizziness, fatigue, emaciation, hair loss and other symptoms, which will cause damage to the human body.
Nine taboos of using microwave oven
1. Avoid using ordinary plastic containers: first, hot food will deform plastic containers; second, ordinary plastics will release toxic substances, pollute food and endanger human health. Use a special microwave oven to hold food and put it in the microwave oven for heating.
2. Avoid using metal utensils: As the utensils such as iron, aluminum, stainless steel and enamel are put into the furnace, electric sparks will be generated when the microwave oven is heated, which will not only damage the furnace body, but also heat uncooked food.
3. Avoid using closed containers: use wide-mouth containers when heating liquids, because the heat generated by food heating in closed containers is not easy to dissipate, which makes the pressure in the containers too high and easily leads to blasting accidents. Even if you cook food with shells, you should pierce the shells with needles or chopsticks in advance to avoid bursting after heating, splashing out to pollute the furnace wall or hurting people.
4. Avoid overtime heating: food is thawed or heated in the microwave oven. If you forget to take it out, throw it away after more than 2 hours to avoid food poisoning.
5. Don't heat the meat until it is half-cooked, and then put it in the microwave oven for heating: because the half-cooked food will still breed bacteria, it is impossible to kill all the bacteria when it is put in the microwave oven for the second time because the time is too short. Frozen meat must be thawed in the microwave oven before it is heated and cooked.
6. Avoid freezing the meat thawed in the microwave oven again: Because the meat thawed in the microwave oven has actually heated the outer layer at a low temperature, and bacteria can reproduce at this temperature. Although freezing can prevent its reproduction, it can't kill the living bacteria. If the meat thawed in the microwave oven is frozen in the refrigerator again, it must be heated until it is fully cooked.
7. Avoid fried food: high-temperature oil will splash and cause fire. In case of accidental fire in the furnace, don't open the door, turn off the power first, and then open the door to cool down after the fire is extinguished.
8. Avoid putting the oven in the bedroom, and be careful not to cover the cooling window grille on the microwave oven with objects.
9. Avoid working in front of the microwave oven for a long time: After turning on the microwave oven, people should stay away from the microwave oven or at least 1 m away from the microwave oven.
How to remove stubborn dirt from microwave oven
If the microwave oven is not wiped immediately after use, it is easy to form oil dirt inside, so we should use special tricks to remove the dirt: put a container filled with hot water in the microwave oven, heat it for two or three minutes, and let the microwave oven be filled with steam, so as to soften the stubborn dirt, because it is full of water and easy to remove.
When cleaning, first wipe it with diluted water of neutral detergent, and then clean it with clean water-washed rags and dry rags respectively. If you still can't remove stubborn dirt, you can scrape it off with something like a plastic card, and never scrape it with a metal sheet to avoid hurting the inside. Finally, don't forget to open the door of the microwave oven and let it dry thoroughly.