how induction stove works

[Abstract】Induction cooker is a kind of induction stove commonly used in our daily life to cook food. This paper mainly introduces the principle of induction and the working principle of induction type induction cooker.

【Key words】Electromagnetic induction; eddy current; induction cooker


0 Introduction

An induction cooker applies the electromagnetic induction principle for healing work, an advanced electronic cooker for modern home cooking. It is an advanced electronic cooking appliance for modern home cooking. It is very convenient and can be used for cooking, frying, pan-frying, steaming, stir-frying, and others. It can use to cook, fry, pan-fry, steam, stir fry and other cooking operations. Features: fast temperature rise, high thermal efficiency, no open flame, no smoke, no harmful gas, no heat radiation to the surrounding environment, compact size, good safety and beautiful appearance, etc. point, can complete most of the cooking tasks of the family, is to realize the modernization of the kitchen indispensable The new electronic stove is indispensable for modernizing the kitchen.


1 Faraday's principle of electromagnetic induction

The British physicist Faraday discovered electromagnetic induction, also known as magneto-electric induction, in which a conductor placed in a changing magnetic flux generates an electric potential. This electric potential is called the induced or induced electric potential. If the conductor is closed into a circuit, the electric potential will drive the flow of electrons, forming an induced current (induced current).


It represents the induced electric potential along a closed-loop equal to the rate of change of the magnetic flux passing through the area enclosed by the closed-loop. For maintaining a current in a closed-loop conductor, the electric field must exist within the conductor. The induced potential electricity can be defined in terms of the intensity of the induced electric field within the conductor.


2 Common heating methods

There are usually two methods of heating using high-frequency voltage or current: dielectric heating and induction heating.

Dielectric heating is the use of high-frequency voltage heating, usually used to heat non-conductive materials. When the high-frequency voltage is applied to the two-pole plate layer, it will produce an alternating electric field between the two poles. The medium to be heated is in the alternating electric field. The polar molecules or ions in the medium will do the same frequency rotation or vibration with the electric field, thus generating heat and achieving the heating effect. For example, microwave oven heating.

Induction heating is the use of high-frequency current heating through the electronic circuit board components to generate the alternating magnetic field, when the bottom of the pot with iron pots and pans placed on the stove surface, pots and pans that cut the alternating magnetic lines and pots and pans in the bottom of the metal part of the alternating current, eddy current so that the pot iron molecules high-speed irregular motion, molecules collide with each other, friction and generate heat (so: the heat source of induction cooking from the bottom of the pot and pans rather than Induction cooker heat conduction to the pot itself, so the thermal efficiency than all cookware efficiency are nearly one times higher) so that the appliance itself high-speed heat, used to heat and cook food, to achieve the purpose of cooking, this is the principle of induction heating, induction cooker is the use of this principle to work.


3 Principle of Induction Cooker

3.1 Generation of eddy currents

The movement of a conductor in a magnetic field or a conductor at rest but with a time-varying magnetic field can cause the magnetic lines of force to cut relative to the conductor. As shown in Figure 2, a coil is wound around the outside of a conductor, and the coil is allowed to pass an alternating current, then the coil produces an alternating magnetic field. The conductor in the middle of the coil is equivalent to the closed-circuit in the circumferential direction. The magnetic flux in the closed-circuit is constantly changing, leading to the induced electric potential. The induced current will generate in the circumferential direction of the conductor. The direction of the current turns around like a vortex in the circumferential direction of the conductor.

Therefore, this phenomenon of electromagnetic induction inside the whole conductor and the generation of the induced current is called the eddy current phenomenon. The eddy current inside the conductor generates heat, and if the resistivity of the conductor is small, the eddy current is powerful, and the heat generated is immense.


图 2 电涡流原理图绝缘栅双极型晶体管


3.2 Principle of Induction Cooker

The current voltage is converted into direct current by rectifier, and the direct current is changed into a high-frequency alternating current over audio by a high-frequency power conversion device. The high-frequency alternating current is added to the flat hollow spiral induction heating coil, which generates a high-frequency alternating magnetic field. The magnetic lines of force penetrate the ceramic table of the cooktop and act on the metal pot. The pots and pans cut the alternating magnetic lines and produce eddy currents in the metal part of the bottom of the pots and pans so that the iron molecules of the pots and pans move at high speed and irregularly. The molecules collide and rub against each other to produce heat energy, which is used to heat and cook food for achieving cooking.




3.3 Main circuit diagram of induction cooker

Figure 3 shows the primary circuit of the induction cooker. 220V, 50Hz AC power is rectified by a high power full-bridge, and the rectified DC power is pulsating, and the pulsating DC power is smoothed and filtered by the choke L1 and C1. The relatively smooth DC power is supplied to the lower induction coil L2. The L2 coil and C2 oscillation capacitor form the L2C2 oscillation circuit to generate an alternating magnetic field on the coil. IGBT is the abbreviation of Insulated Gate Bipolar Transistor, composed of BJT (bipolar triode) and MOS (insulated gate field effect tube).

(Insulated Gate Field Effect Transistor) is a compound fully controlled voltage-driven power semiconductor device with the advantages of the high input impedance of MOSFET and low on-state voltage drop of GTR?


There are three electrodes, called gate G, collector C and emitter E. The rear stage of the electromagnetic coil is the high-voltage protection diode VD, which prevents the reverse high voltage from breaking through the IGBT. When the C-pole voltage of the IGBT is 0V, the IGBT is on, and the excitation coil is storing energy at this time. As the IGBT turns off, the inductor can only charge the capacitor C2, which causes the voltage of the C-pole to rise, and the voltage of the C-pole is highest when the charging current becomes more minors until zero. From this point on, capacitor C2 starts to discharge through the coil, and the C-pole voltage decreases.

When the C-pole voltage drops to 0V, the control circuit detects this value, and the IBGT turns on again, thus creating an oscillation.




4 Conclusion

With the continuous progress of science and technology and the continuous improvement of living standards, induction cookers have gone into thousands of households. It breaks the traditional open fire cooking method using magnetic field induction current (also known as eddy current) heating principle to heat and cook food, known as the "green stove." The working principle of the magnetic stove is straightforward, and we expect newer electronic products can enter our We expect that more and newer electronic products will come into our homes to serve our work and life better.

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