Electric cooking stoves are kitchen appliances that use electric heating elements to heat food.At the beginning of the 20th century, GA. Hughes made the world's first electric cooker, called the electrified gas cooker.In the 1930s, timing and temperature control were improved.Self cleaning electric cooker appeared in 1963.In the same yearGlassware and CeramicsThe electric stove of.
The principle of electric cooker is to use the heat emitted when the current passes through the resistance wire (tungsten wire, the same as the material in the incandescent lamp) with great resistance to heat.
Electromagnetic stoveIt is to generate alternating magnetic field through electronic circuit board components. When the bottom of the iron containing cooker is placed on the furnace surface, the cooker cuts the alternating magnetic line of force and generates alternating current (i.e. eddy current) on the metal part at the bottom of the cooker. The eddy current makes the iron molecules of the cooker move irregularly at high speed, and the particles collide with each otherHeat energy is generated by friction (therefore, the heat source of the induction cooker cooking comes from the bottom of the cooker rather than from the induction cooker itself, so the heat efficiency is nearly 1 times higher than that of all cookware), which makes the appliance itself heat at high speed to heat and cook food, so as to achieve the purpose of cooking.
Electric cookers can be divided into free placement type and built-in type (embedded in the kitchen counter) according to the installation mode;According to the type of stove heater, it can be divided into full electric type and electric gas dual-use type (exceptElectric heaterIn addition, there are 1-2 gas heaters).
The electric cooker is composed of a shell, an electric heating element and a temperature control and timing system: ① The shell: including the box, the control panel and the door, all made of thin steel plate.All surfaces subject to high temperature shall be coated with enamel.The box has two layers, which can be filled with thermal insulation materials or air interlayer.The box door is equipped withHeat-resistant glassAt the same time, it is also equipped with an interlocking mechanism, which can automatically cut off the power supply when opening the door. ②Electric heating elements: there are two types of heating elements: stove heating elements and hearth heating elements.The heating element of the stove is installed on the table top of the stove, which can heat all kinds of pots and pans.Its typical form is a metal tube type electric heating element bent into a disc, with adjustable or fixed power.The heating element of the hearth is installed inside the hearth for baking food.It is usually composed of upper baking element and lower baking element, usually metal tube type. ③Temperature control and timing system: the temperature control and timing of the electric cooker are mainly used for the hearth.Temperature control adoptsBimetallic sheetType or temperature sensing package type temperature controller, clockwork type, electric type or electronic type timer is used for timing.The total power of electric cookers is relatively large, generally more than 2kW, and some can reach more than 10kW. Pay special attention to overload safety when installing and using.
Installation mode
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Electric cookers can be divided into free placement type and built-in type (embedded in the kitchen counter) according to the installation mode;According to the type of stove heater, it can be divided into full electric type and electric gas dual-use type (in addition to electric heater, there are also 1-2 gas heaters).
system composition
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The electric cooker is composed of shell, electric heating element and temperature control timing system:
① Housing.The box, control panel and door are all made of thin steel plate.
② Electric heating element.There are two types of heating elements: stove heating element and hearth heating element.The heating element of the stove is installed on the table top of the stove, which can heat all kinds of pots and pans.Its typical form is a metal tube type electric heating element bent into a disc, with adjustable or fixed power.The heating element of the hearth is installed inside the hearth for baking food.It is usually composed of upper baking element and lower baking element, and the common one is metal tube type.
③ Temperature control and timing system.The temperature control and timing of the electric cooker are mainly used for the hearth.The bimetallic chip type or temperature sensing package type temperature controller is used for temperature control, and the clockwork type, electric type or electronic type timer is used for timing.
Ordinary electric cooker
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Ordinary electric cooker is composed of enclosed typeelectric furnaceAnd an electric oven.The tubular heating element of the closed electric furnace is buried in the heating plate on the furnace surface of cast iron or aluminum alloy, isolated from the air, which can prevent oxidation, and the thermal efficiency is 10% higher than that of the open electric furnace, which can reach more than 65%.The diameter and power of enclosed electric furnaces are different to meet the use requirements of different sizes of pots and tools.
Microwave oven
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Microwave cooker A new type of electric cooker that uses microwave energy to cook food.It is composed of power transformer, rectifier, microwave generator (magnetron), transmission waveguide, agitator (fan), box, oven door, controller, etc. (see the internal structure of microwave oven in the figure).The main structural parts are waveguide, furnace chamber and door.
The waveguide is a rectangular metal tube used to transmit microwave emitted by magnetron.One end of the waveguide is connected to the antenna of the magnetron, and the other end is fed from the upper part of the box.The waveguide also defines the waveform of the electromagnetic field.The furnace chamber is mostly a metal box composed of aluminum, stainless steel and other metals.When the microwave in the oven cavity that is not absorbed by food reaches the oven wall, it can be reflected back to penetrate the food and be absorbed.The furnace door is mainly composed of a metal frame and a glass observation window, which is closely connected with the furnace cavity.
When in use, the mains power is boosted by the power transformer, then transformed into DC power to supply the magnetron after being rectified and filtered by the current stabilizer and capacitor, and 2450MHz microwave is generated in the magnetron.Microwave energy is transmitted through the waveguide, and then reflected to the furnace cavity by the stirrer, which is continuously absorbed by food.The molecules in the food oscillate back and forth under the action of the alternating electric field (the number of oscillations reaches hundreds of millions to billions of times per second), that is, the food molecules produce very high oscillations, molecular motion and friction between molecules, so that the food generates enough heat in a very short time, and the food temperature rises rapidly.The power consumption of microwave cooker is only about 20% of that of the same power cooker.
There are two kinds of electric control modes of microwave ovens: universal control and computer control.The universal microwave cooker is equipped with a timing device, and the cooking time and appropriate heating power can be selected according to different foods during use.The computer controlled microwave cooker is equipped with a microcomputer, which can make the microwave cooker defrost, heat and keep warm the food according to the pre selected program.
When microwave oven is in use, it cannot be burned empty, otherwise, the magnetron will be damaged because there is no place for microwave absorption;The utensils for storing food in the oven cavity must be non-metallic materials, such as glass, ceramics and high temperature resistant materials. If metal utensils are used, they will reflect microwave and interfere with the normal operation of the oven cavity, or even cause high-frequency short circuit, which will damage the microwave range;magnetic material Don't get close to the microwave oven to avoid interfering with the microwave magnetic field;Regularly check the microwave leakage;The power must be cut off when repairing the microwave oven.
Electromagnetic stove
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The electromagnetic cooker is a new type of electric cooker made of the principle of electromagnetic induction heating.It is composed of high-frequency induction heating coil (i.e. excitation coil), high-frequency power conversion device, controller, ferromagnetic material pot bottom cooker and other parts.The high-frequency induction heating coil is a circular heating coil placed horizontally under the panel of the heating part. Under the heating coil framework, three bar magnets are regularly placed to form a magnetic circuit with the bottom of the pot.
When in use, the heating coil is connected with alternating current, and an alternating magnetic field is generated around the coil.When the electromagnetic cooker panel is not placedFerromagnetic materialWhen cooking utensils at the bottom of the pot, the magnetic circuit of this alternating magnetic field is basically an air magnetic circuit, with a large magnetic resistance, so the heating coil only consumes no-load current.When the cooker is put on, most of the magnetic force lines of the alternating magnetic field pass through the metal pan body, generating a large number of eddy currents in the bottom of the pan, thus generating the heat required for cooking.The heat generated by the electromagnetic cooker is only in the pot itself, and its panel (usually made of hard plastic or impact resistant ceramic plate) does not generate heat, that is, there is no open fire during the heating process, so it is safe, clean and sanitary.
Electromagnetic cookers can be divided into low frequency (i.e. power frequency, 50Hz or 60Hz) and high frequency (above 15kHz) according to the frequency of induction heating current.High frequency electromagnetic cookers have high heating efficiency and low vibration noise. Most of the electromagnetic cookers used are high-frequency electromagnetic cookers.
Control system
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The control system includes high-frequency conversion circuit, output power adjustment circuit, power (status) display circuit and safety protection circuit.The function of the high-frequency conversion circuit is to convert the DC output from the rectifier circuit into high-frequency current and supply it to the high-frequency induction heating coil.Different foods have different cooking requirements, that is, different temperatures. This can change the output power through the output power adjustment circuit and be displayed on the power (status) display.The safety protection circuit has a load detection device, a component heating prevention device, an overheating protection device, a safety device, and an electromagnetic cooker panel fracture detection device.
matters needing attention
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When using the electric cooker, do not close to other high temperature heat sources or damp places to avoid excessive temperature rise or moisture in the cooker;There are many charged bodies in the electromagnetic cooker. Do not poke the air inlet and air outlet with a metal rod or needle to avoid accidents;Cooking utensils shall be pig iron, wrought iron and magnetic stainless steel pan;Do not exceed the specified continuous startup time during use;The voltage of the electromagnetic cooker must be consistent with the grid voltage, or high or low voltage will damage the electromagnetic cooker. If necessary, a voltage regulator should be used to ensure that the voltage of both is consistent.
