Introduction to Microwave Oven Microwave Oven, as its name implies, is to use microwave to cook and cook. Microwave oven is a modern cooking stove that uses microwaves to heat food. 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 refers to the radio wave with the wavelength of 0.0 1 ~ 1 m, and its corresponding frequency is 30000 MHz ~ 300 MHz. In order not to interfere with communication systems such as radar, the working frequency of microwave ovens is mostly 9 15 MHz or 2450 MHz. The microwave oven consists of power supply, magnetron, control circuit and cooking cavity. The power supply provides a high voltage of about 4000 volts to the magnetron. Under the excitation of the power supply, the magnetron continuously generates microwaves, which are coupled into the cooking cavity through the waveguide system. There is a rotatable agitator near the entrance of the cooking cavity. Because the agitator is a fan-shaped metal, it can reflect microwave in all directions after rotation, so the microwave energy can be evenly distributed in the cooking cavity. The power range of microwave oven is generally 500 ~ 1000 watt. Basic structure ① Safety interlock switch of oven door-ensure that the oven door is open and the microwave oven can't work, and the microwave oven can only work when the oven door is closed; ② Video window-with metal shielding layer, which can observe the cooking situation of food through the grid; (3) ventilation-ensure good ventilation when cooking; ④ turntable support-driving the glass turntable to rotate; ⑤ Glass turntable-the container for holding food is placed on the turntable, and when heated, the turntable rotates to make the food cooked evenly; ⑥ Control panel-controls the cooking in all files; ⑦ Door switch-Press this switch to open the door. Working principle (1) furnace cavity. 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 waterproof groove structure is a stable and reliable 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 working time to stopping time when the magnetron works intermittently), so as to adjust 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. The principle of microwave heating The principle of microwave heating is simply that when microwave is radiated to food, food always contains a certain amount of water, and water is composed of polar molecules (even if there is no external electric field, the positive and negative charge centers of molecules do not coincide), and the orientation of this polar molecule will change with the change of microwave field. Due to the movement of polar water molecules in food. As well as the interaction between adjacent molecules, it produces a phenomenon similar to friction, which makes the water temperature rise, so the temperature of food also rises. The food heated by microwave is heated at the same time, so that the whole object is heated evenly and the heating speed is fast. The method of cooking food by microwave was first thought of by Percy Spencer, who once made magnetron for Raytheon Company. One day, while he was studying an activated radar device, he suddenly found that the chocolate he had put in his pocket had melted. After Percy Spencer's thinking and research, it was found that his chocolate was melted by microwave. Do not use microwave oven 1. Avoid using ordinary plastic containers: first, hot food will deform plastic containers, and second, ordinary plastics will release toxic substances, pollute food and endanger human health. Use special microwave utensils to hold food and put it in the microwave oven for heating. 2. Avoid using metal utensils: Because the utensils such as iron, aluminum, stainless steel and enamel put into the oven will generate electric sparks when heated in the microwave oven, reflecting microwaves, 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 use shells to cook food, you should pierce the shells with needles or chopsticks in advance to avoid bursting after heating, splashing out to pollute the furnace wall or injuring 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. Cleaning the microwave oven If the microwave oven is not wiped immediately after use, it is easy to form oil dirt inside, so we have to use special tricks to remove the dirt: put the container full of hot water in the microwave oven for two or three minutes to make the microwave oven full of steam, which will make the stubborn dirt soft and easy to remove, because it is full of water. 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. 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. Advantages and disadvantages of microwave oven Because of the short cooking time, microwave oven can well retain vitamins and natural flavor in food. 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. Although the microwave oven is fast, its harm is little known. As early as 196 1, American scientist Gordon found that the microwave of microwave oven caused acetylcholine (a hormone substance) to accumulate along nerve fibers in human body, even if the microwave emission of microwave oven was extremely weak, it would cause many diseases. Not long after, this discovery was confirmed by Dalda Hong, a researcher at the French Curie Foundation. The electromagnetic leakage of microwave oven (which is very small due to safety measures) will lead to burns that will never heal. The microwave oven can destroy the magnetic field structure with a radius of 3-5 meters, and the magnetic field generated by human cell oscillation will be disturbed near the microwave oven. According to the experiments of American researchers, staying near the microwave oven for a long time will lead to a slow heartbeat. After a day's work, you will feel pain all over, sleep will be disturbed, and your memory will change. In addition, the damage of microwave oven to food is terrible. Foods that have been "cooked" or thawed only once will no longer have any active vitamins, leaving only some calories in the stomach. Therefore, people can't often use microwave ovens for convenience. In addition, people who use microwave ovens should eat more diets containing vitamins (lettuce, coarse grains, etc.). ) to maintain the energy needed by the human body.