Dual-purpose electromagnetic induction heating coil for pan with flat bottom and concave bottom and design method thereof

Abstract

The invention discloses a dual-purpose electromagnetic induction heating coil for a flat-bottom pot and a concave-bottom pot, which comprises a single spirally wound single-wire wound uniform heating inner coil, and a plurality of circles of rewinding magnetic field enhancing outer coils are sequentially and coaxially wound outside the single-wire wound uniform heating inner coil. The invention further discloses a design method of the dual-purpose electromagnetic induction heating coil for the flat-bottom pot and the concave-bottom pot. The problem that an existing electromagnetic heating coil cannot heat a pan and a concave bottom pan at the same time is solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of magnetic heat treatment, and relates to a flat and concave bottom pot dual-purpose electromagnetic induction heating coil, and also relates to a design method of the flat and concave bottom pot dual-purpose electromagnetic induction heating coil. BACKGROUND

[0002] At present, the induction heating technology is widely applied in the kitchen appliance field due to the advantages of fast heating response, high thermal efficiency, accurate temperature control, good safety and clean environmental protection. The electromagnetic induction heating coil is a core component for realizing energy conversion of the electromagnetic oven, and the structural design and electromagnetic characteristics of the electromagnetic induction heating coil have important influences on the heating efficiency and temperature distribution of the electromagnetic oven.

[0003] It will significantly increase the structural complexity and cost to respectively set special coils for the flat bottom pot and the concave bottom pot, and therefore it is a practical requirement in the electromagnetic field to develop a general induction heating coil capable of simultaneously adapting to the flat bottom pot and the concave bottom pot. When the flat bottom pot is heated by using the planar induction coil for the flat bottom pot, the distance between the side wall area of the concave bottom pot and the coil is increased, which leads to the obvious attenuation of the magnetic induction intensity of the side wall area, and there is a heating shortage in the side wall area. When the flat bottom pot is heated by using the three-dimensional enhanced induction coil for the concave bottom pot, the bottom surface of the flat bottom pot is a planar structure, which is not compatible with the three-dimensional structure of the concave coil, the magnetic field coupling between the coil and the flat bottom pot is low, which not only reduces the magnetic field utilization efficiency, but also causes the redundancy and waste of the coil material. In addition, during the heating process of the concave bottom pot, due to the difference in the radial distance between the pot wall and the coil, the magnetic induction intensity of the side wall area is insufficient, and thus the defect of insufficient temperature rise in the side wall area of the concave bottom pot occurs. Therefore, it is urgent to design a flat and concave bottom pot dual-purpose electromagnetic induction heating coil, and to improve the temperature of the side wall area of the concave bottom pot by designing the coil structure and the power supply mode. SUMMARY

[0004] The purpose of the present application is to provide a flat and concave bottom pot dual-purpose electromagnetic induction heating coil, which solves the problem that the existing electromagnetic heating coil cannot simultaneously heat the flat bottom pot and the concave bottom pot.

[0005] Another purpose of the present application is to provide a design method of the flat and concave bottom pot dual-purpose electromagnetic induction heating coil.

[0006] The first technical solution adopted by the present application is a flat and concave bottom pot dual-purpose electromagnetic induction heating coil, which comprises a single spiral winding circumferential uniform heating inner coil, and a plurality of turns of a return magnetic field enhancement outer coil are coaxially wound outside the circumferential uniform heating inner coil.

[0007] The second technical solution adopted by the present application is a design method of the flat and concave bottom pot dual-purpose electromagnetic induction heating coil, which comprises a single wire circumferential uniform heating inner coil inner diameter , a single wire circumferential uniform heating inner coil inner diameter The radius of cross-section of each layer of conductor in the coil Number of conductor strands N in the coil, and the cross-sectional radius of the coil. d s Single-wire winding for uniform heating, inner coil turn spacing The number of turns of the inner coil for uniform heating by a single wire m The radial distance *s* between the outermost turn of the inner coil for uniform heating with a single conductor and the innermost turn of the outer coil for enhancing the magnetic field; the inner diameter of the outer coil for enhancing the magnetic field. Outer diameter of the rewinding magnetic field enhancement outer coil Spacing between coils in the same group of outer coils for magnetic field enhancement Spacing between adjacent groups of coils in the outer coil of the rewinding magnetic field enhancement coil The resonant capacitance of each group of coils in the outer coil that enhances the magnetic field. The design process.

[0008] The second technical solution of the present invention is further characterized by:

[0009] Single wire surrounds the inner diameter of the uniform heating coil The design process is as follows: Considering the distribution of the magnetic field at the center of the inner coil for uniform heating by a single conductor Generating eddy current density inside the cookware This determines the temperature distribution between the center and edge areas of the cookware bottom. A single wire is wound around the inner diameter of the uniformly heated inner coil. The design formula is: (1) in, The permeability of free space, The operating frequency of the induction cooker. The magnetic permeability of the cookware material. The electrical conductivity of the cookware material. Density of cookware material Specific heat capacity of the cookware material; The single-wire coil is used to uniformly heat the inner diameter of the inner coil. The design process is as follows: Based on the equivalent mathematical model of cookware size The magnetic field distribution of the inner coil, which is uniformly heated by a single conductor, is designed to be equivalent to elliptical contour lines. A single wire is used to uniformly heat the inner coil. The design formula is as follows: (2) in, h The height of the concave-bottomed pot. k This is the ratio of the height of the bottom of the pot to the total height of the pot.

[0010] Cross-sectional radius of each layer of wire of the coil The design process is as follows: Cross-sectional radius of each layer of wire of the coil The same, The design formula is as follows: (3) Wherein, The material resistivity of the single-wire loop uniformly heated inner coil and the magnetic field enhanced outer coil, z The number of wire strands of the first z layer; The design process of the number of wire strands N of the coil is as follows: Since there are N strands of wire in the single-wire loop uniformly heated inner coil and the magnetic field enhanced outer coil, the design formula of the number of wire strands N is as follows: (4) Wherein, I The designed working current of the electromagnetic oven, The natural heat exchange coefficient of the coil and air; Cross-sectional radius of the coil d s The design process is as follows: Cross-sectional radius of the coil d s The same, d s The design formula is as follows: (5) Wherein, x The number of wire layers of the coil.

[0011] Turn spacing of the single-wire loop uniformly heated inner coil The design is as follows: The functional relationship between the turn spacing of the nth turn of the coil and the voltage distribution is established, and the turn spacing of the single-wire loop uniformly heated inner coil The design formula is as follows: (6) Wherein, n is the numerical value of the nth turn of the coil, and C is Euler's constant; The design process of the number of turns of the single-wire loop uniformly heated inner coil m The design process is as follows: Based on the inductance energy storage mechanism And the equivalent inductance expression of the coil Under the constraint of the correspondence between output power and coil current, a functional relationship between the number of turns m and the power parameter is established, and the number of turns of the inner coil is uniformly heated by a single wire. m The design formula is as follows: (7) in, denoted as the permeability of the coil material.

[0012] The design process for the radial distance s between the outermost turn of the inner coil for uniform heating with a single conductor and the innermost turn of the outer coil for enhancing the magnetic field is as follows: Since there is a potential difference between the outermost turn of the uniformly heated inner coil and the innermost turn of the magnetically enhanced outer coil, based on the relationship between the potential difference between the two coils and the air breakdown voltage, and under the constraint that the working voltage difference does not exceed the allowable electric field strength of the air breakdown voltage, the design formula for the radial distance s between the outermost turn of the uniformly heated inner coil and the innermost turn of the magnetically enhanced outer coil is as follows: (8) Inner diameter of the outer coil for enhancing the magnetic field The design process is as follows: The inner diameter of the outer coil for enhancing the magnetic field is determined by introducing the coil turn spacing based on the outer diameter of the outer coil for enhancing the magnetic field. The design formula is as follows: (9) Outer diameter of the rewinding magnetic field enhancement outer coil The design process is as follows: The magnetic field distribution within the heating region is equivalent to a hyperbolic model. Establish a rewinding magnetic field to enhance the outer diameter of the outer coil r oo The functional relationship between voltage parameters and cookware dimensions, and the outer diameter of the rewinding magnetic field enhancement coil. r oo The design process is as follows: (10) in, R This refers to the diameter of the pot's opening.

[0013] Spacing between coils in the same group of outer coils for magnetic field enhancement The design process is as follows: taking a single conductor at a vertical height of... The maximum value of the alternating magnetic field generated at that location As a reference, a magnetic field maintenance coefficient is introduced to maintain the magnitude of the magnetic field between the two conductors. To ensure that the midpoint of two adjacent wires is directly above The magnetic field generated at that location is equal to , magnetic induction intensity is Therefore, the design formula of the spacing between adjacent groups of coils of the return magnetic field enhanced outer coil is as follows: (11) Wherein, the magnetic field maintenance coefficient is

[0014] The design process of the spacing between adjacent groups of coils of the return magnetic field enhanced outer coil is as follows: taking the minimum value of the alternating magnetic field generated by a single wire at a distance of the vertical height of the wire as the reference, in order to ensure that the magnetic field between the two wires is greater than the reference value, the magnetic field superposition coefficient is introduced, and in order to ensure that the magnetic field generated at the midpoint directly above the two adjacent wires is equal to , the magnetic induction intensity is Therefore, the design formula of the spacing between adjacent groups of coils of the return magnetic field enhanced outer coil is as follows: (12) Wherein, the magnetic field superposition coefficient is , and the phase angle of the current flowing through the return magnetic field enhanced outer coil is

[0015] The design process of the resonant capacitance of each group of coils of the return magnetic field enhanced outer coil is as follows: based on the coil-pan coupling model and the resonant equivalent impedance model , the design formula of the resonant capacitance of each group of coils of the return magnetic field enhanced outer coil is as follows: (13) Wherein, the number of the i-th group of single-turn return magnetic field enhanced outer coils is i , the pan shape coefficient is k , and the corresponding inductive heating coil resistance is obtained by the following formula: R i (14) The beneficial effects of the present application are that the same electromagnetic induction heating coil can efficiently heat flat-bottomed pots and concave-bottomed pots by designing the coil structure parameters, reducing the complexity of the structure and the manufacturing cost; at the same time, by adopting the power supply mode of opposite current for adjacent groups of coils of the single-turn return magnetic field enhanced outer coil, the magnetic field is superimposed in the pot wall area, which significantly improves the temperature of the side wall of the concave-bottomed pot. BRIEF DESCRIPTION OF DRAWINGS ​​​​​​​​​

[0016] Figure 1 Structure diagram of the electromagnetic induction heating coil for the dual-purpose flat-bottomed and concave-bottomed pot of the present application; Figure 2 Method diagram of the connection between the electromagnetic induction heating coil for the dual-purpose flat-bottomed and concave-bottomed pot of the present application and the induction heating power supply; Figure 3 Layout diagram of the electromagnetic induction heating coil for the dual-purpose flat-bottomed and concave-bottomed pot of the present application and the heating pot; Figure 4 Design diagram of the current flow direction of the induction heating power supply of the port of the electromagnetic induction heating coil for the dual-purpose flat-bottomed and concave-bottomed pot of the present application; Figure 5 Design and laying scheme diagram of the internal single wire of the multi-strand wire used by the electromagnetic induction heating coil for the dual-purpose flat-bottomed and concave-bottomed pot of the present application; Figure 6 Mechanism diagram of the magnetic field enhancement of the external single-turn return magnetic field enhancement coil of the electromagnetic induction heating coil for the dual-purpose flat-bottomed and concave-bottomed pot of the present application; Figure 7 Induction eddy current distribution diagram of the concave-bottomed pot in the heating process of the electromagnetic induction heating coil for the dual-purpose flat-bottomed and concave-bottomed pot of the present application; Figure 8 Temperature field distribution of the concave-bottomed pot heated by the electromagnetic induction heating coil for the dual-purpose flat-bottomed and concave-bottomed pot of the present application; Figure 9 Temperature field distribution of the flat-bottomed pot heated by the electromagnetic induction heating coil for the dual-purpose flat-bottomed and concave-bottomed pot of the present application. DETAILED DESCRIPTION

[0017] The present application will be described in detail below with reference to specific embodiments.

[0018] Embodiment 1 The electromagnetic induction heating coil for the dual-purpose flat-bottomed and concave-bottomed pot of the present application, as shown in the figure, mainly includes the following parameters: Figure 1 The inner diameter of the single-wire ringed and uniformly heated inner coil The outer diameter of the single-wire ringed and uniformly heated inner coil The turn spacing of the single-wire ringed and uniformly heated inner coil The number of turns of the single-wire ringed and uniformly heated inner coil m， The radial distance s between the outermost turn of the single-wire ringed and uniformly heated inner coil and the innermost turn of the return magnetic field enhancement outer coil The inner diameter of the single-turn return magnetic field enhancement outer coil The spacing between the coils in the same group of the single-turn return magnetic field enhancement outer coil group The spacing between the coils in adjacent groups of the single-turn return magnetic field enhancement outer coil group .

[0019] Embodiment 2 The present invention relates to a method for connecting an electromagnetic induction heating coil and an induction heating power supply for both flat and concave bottom pans, as follows: Figure 2 As shown, the system mainly includes a power supply module, a rectifier module, a filter module, an inverter module 1, an inverter module 2, and an electromagnetic induction heating coil suitable for both flat and concave bottom pans. Inverter module 1 is connected to multiple resonant capacitors. , ... Connected to the single-turn wound magnetic field enhancement outer coil group, inverter module 2 is connected via a resonant capacitor. It is connected to a single-wire-wound inner coil for uniform heating.

[0020] Example 3 The present invention relates to an electromagnetic induction heating coil and heating cookware layout suitable for both flat and concave bottom pots, as follows: Figure 3 As shown, the main parameters of the cookware include: cookware opening diameter R, cookware wall thickness, etc. Cookware height h .

[0021] Example 4 The design method of the electromagnetic induction heating coil for both flat and concave bottom pans of this invention is as follows: 1) Description of known parameters: in, h 0 represents the distance between the induction heating coil and the bottom of the pot. m ), Heating time for induction cooker ( s ), Operating frequency of the induction cooker , The wall thickness of concave-bottomed and flat-bottomed pans ( m ), R The diameter of the concave bottom pot opening ( m ), To allow for a temperature difference (°C) between the center of the cookware and the bottom edge of the cookware, The operating voltage (V) of the inner coil of the induction cooker's uniform heating element. The operating voltage of the outer coil for enhancing the single-turn magnetic field of the induction cooker is Δ. T To allow the induction cooker coil to operate and heat up (°C), This represents the breakdown voltage (V) of air between adjacent conductors. The operating current (A) for the inner coil of the induction cooker, which is uniformly heated by a single wire, is given. The operating current (A) of the outer coil for enhancing the single-turn magnetic field of the induction cooker. Output power of the induction cooker .

[0022] 2) Single wire wraps around the inner coil for uniform heating of the inner diameter (m) design like Figure 1 As shown, a uniform temperature distribution between the central area of ​​the cookware's bottom and the perpendicular portion of the edge of the uniformly heating inner coil is a crucial indicator for the induction heating coil's ability to heat the cookware. This is considered in the design of the magnetic field distribution at the center of the uniformly heating inner coil. Generating eddy current density inside the cookware This determines the temperature distribution between the center and edge areas of the cookware bottom. Therefore, the inner diameter of the inner coil is uniformly heated by a single wire. The design method is as follows: (1) in, The permeability of free space, Operating frequency of the induction cooker , For the magnetic permeability of cookware materials , Electrical conductivity of cookware materials , Density of cookware material , Specific heat capacity of cookware material .

[0023] 3) Single wire wraps around the outer diameter of the inner coil for uniform heating The design of (m) is as follows: like Figure 1 As shown, the design of the outer diameter of the single-wire-wound uniform heating inner coil aims to ensure that the magnetic field generated by the coil can effectively cover the bottom area of ​​the cookware, resulting in a reasonable heating distribution along the height of the cookware. When the height of the magnetic field exceeds the effective heating height of the cookware by a certain proportion, the magnetic field in the cookware wall area weakens significantly. Therefore, when determining the outer diameter of the single-wire-wound uniform heating inner coil, the influence of the cookware height and the spatial distance between the coil and the cookware on the magnetic field distribution range should be considered. This is based on an equivalent mathematical model of the cookware dimensions. The magnetic field distribution of the inner coil, which is uniformly heated by a single conductor, is designed to be equivalent to elliptical contour lines. A single wire is used to uniformly heat the outer diameter of the inner coil. The design method is as follows: (2) in, h The height of the concave-bottomed pot (m). k It is the ratio of the height of the bottom of the pot to the total height of the pot, ranging from 0.25 to 0.40.

[0024] 3) Radius of cross-section of each layer of multi-strand conductor The design of (m) is as follows: like Figure 4The designed cross section radius of each layer of the multi-strand wire is the cross section radius of the single wire winding the inner coil for uniform heating and the outer coil for magnetic field enhancement. Under high frequency working condition, the current distribution on the cross section of each strand of the multi-strand wire is uneven due to the joint effect of the skin effect and the proximity effect. Especially when the magnetic field coupling between adjacent strands is enhanced, the equivalent high frequency resistance of each strand is different, which leads to the concentration of local current density and thus causes uneven heating distribution and increased additional loss. In order to weaken the influence of the proximity effect on the uniformity of the current distribution of each strand, the high frequency equivalent impedance of the single strand is controlled by designing the cross section radius of each layer of the multi-strand wire , so that the current distribution of each strand under high frequency condition tends to be balanced, thereby reducing local additional loss and improving wire utilization. Therefore, the design method of the cross section radius of each layer of the multi-strand wire is as follows: (3) , where is the resistivity of the material of the single wire winding the inner coil for uniform heating and the outer coil for magnetic field enhancement z , and z is the layer number of the wire strand, and the innermost layer is numbered as 1.

[0025] 4) The design of the coil wire strand number N is as follows: The designed coil wire strand number N is the wire strand number of the single wire winding the inner coil for uniform heating and the outer coil for magnetic field enhancement. Under the action of the proximity effect and the alternating current skin effect, the high frequency equivalent resistance of each strand of the multi-strand wire will change, and if the strand number is not set reasonably, it will lead to increased alternating current loss and concentrated heating of the coil, thereby affecting the coil temperature rise distribution and electromagnetic efficiency. The designed coil wire strand number N is the wire strand number of the single wire winding the inner coil for uniform heating and the single coil winding the outer coil for magnetic field enhancement. Considering the corresponding relationship between the alternating current loss and the temperature rise of the wire under the action of high frequency current, based on the alternating current resistance model and the thermal equilibrium model, a functional relationship between the wire strand number and the allowable temperature rise is established, so the design method of the coil wire strand number N is: (4) I , where is the natural heat exchange coefficient between the coil and the air.

[0026] 5) The design of the cross section radius of the induction heating coil d s (m) As Figure 4 ​​​As shown, the current distribution and equivalent impedance of an induction heating coil composed of multi-strand wires are closely related to the overall equivalent cross-sectional area of ​​the wires under high-frequency operation. Without modeling the equivalent cross-section of the multi-strand wires, it is difficult to accurately characterize their electromagnetic and thermal properties. The cross-sectional radius of the designed induction heating coil is the cross-sectional radius of a single-wire-wound uniformly heated inner coil and a single-turn magnetic field-enhancing outer coil. Based on the principle of equivalent cross-sectional area, the circular cross-sectional area of ​​the multi-strand wires is equivalent to a square cross-sectional area. By combining the superposition relationship of the cross-sectional radii of each layer of conductors, a correspondence between the equivalent cross-sectional area and the conductor layer structure is established, thereby determining the equivalent cross-sectional radius of the induction heating coil. d s Therefore, the cross-sectional radius of the induction heating coil d s The design method is as follows: (5) in, x This represents the number of coil wire layers.

[0027] 6) Uniform heating with a single wire winding, inner coil turn spacing (m) design like Figure 1 As shown, in a uniformly heated inner coil with a single conductor, there is a potential difference between the turns. If the inter-turn spacing is not set properly under high-frequency operation, excessive electric field strength can lead to localized breakdown. Based on the inter-turn potential distribution model and the air breakdown field strength condition, and under the constraint that the operating voltage does not exceed the critical field strength corresponding to the air breakdown voltage, a functional relationship between the inter-turn spacing of the nth turn and the voltage distribution is established. Therefore, the inter-turn spacing of the uniformly heated inner coil with a single conductor... The design method is as follows: (6) Where n is the value of the nth turn of the coil, and C is Euler's constant, which is 0.577.

[0028] 7) Number of turns of the inner coil for uniform heating with a single wire m Design like Figure 1 As shown, the number of turns *m* of the single-wire winding in the uniform heating inner coil directly determines the coil's inductive energy storage capacity and equivalent impedance. An improperly designed number of turns will lead to an imbalance between the coil and the induction cooker's output power. This is based on the inductive energy storage mechanism. Equivalent inductance expression of coil Under the constraint of the correspondence between output power and coil current, a functional relationship between the number of turns m and the power parameter is established. Therefore, the number of turns of the inner coil for uniform heating by a single conductor is... m The design method is as follows: (7) wherein, is the magnetic permeability of the coil material (H / m).

[0029] 8) The design of the radial distance s (m) between the outermost turn of the inner coil of the single-wire loop uniform heating and the innermost turn of the outer coil of the single-turn return magnetic field enhancement, is as follows: As shown in Figure 1 , there is a potential difference between the outermost turn of the inner coil of the single-wire loop uniform heating and the innermost turn of the outer coil of the single-turn magnetic field enhancement. If the radial distance is not sufficient, air breakdown or insulation failure may occur under high-frequency high-voltage operating conditions, affecting the safe operation of the system. Based on the corresponding relationship between the potential difference between the two coils and the air breakdown voltage, under the constraint that the operating voltage difference does not exceed the air breakdown voltage allowed by the electric field strength, the design method of the radial distance s between the outermost turn of the inner coil of the single-wire loop uniform heating and the innermost turn of the outer coil of the single-turn return magnetic field enhancement is as follows: (8) 9) The design of the inner diameter of the outer coil of the single-turn return magnetic field enhancement (m) As shown in Figure 1 , the inner diameter of the outer coil of the single-turn return magnetic field enhancement is determined by introducing the coil turn spacing based on the outer diameter of the inner coil of the single-wire loop uniform heating, which can be designed as follows: (9) 10) The design of the outer diameter of the outer coil of the single-turn return magnetic field enhancement (m) As shown in Figure 1 , the outer diameter of the outer coil of the single-turn return magnetic field enhancement r oo directly determines the magnetic field coverage and the magnetic field distribution pattern of the heating area of the pot. If the outer diameter is not designed reasonably, the magnetic field distribution will deviate from the target heating area, affecting the heating uniformity. The magnetic field distribution in the heating area is equivalent to a hyperbolic model , and according to the geometric relationship between the hyperbolic equation and the opening size of the pot, the outer diameter of the outer coil of the single-turn return magnetic field enhancement r oo is designed as follows: r oo (10) wherein, R is the opening diameter of the pot (m).

[0030] 11) The design of the spacing between the coils in the same group of the outer coil of the single-turn return magnetic field enhancement (m) ​As shown in Figure 1 , if the distance between the coils in the same group is too large, a magnetic field valley will appear in the central region; if the distance is too small, although a peak will be formed in the center, the peak will still be smaller than the magnetic field generated by a single wire. Therefore, the distance between the coils in the same group in the single-turn return magnetic field enhanced outer coil group should be reduced in design, and the maximum value of the alternating magnetic field generated by a single wire at a vertical height of from the wire is taken as the reference value. In order to maintain the size of the magnetic field in the middle of the two wires, a magnetic field maintenance coefficient is introduced. To ensure that the magnetic field generated directly above the midpoint of the two adjacent wires is equal to , the magnetic induction intensity thereof is . Therefore, the design method of the distance between the coils in the same group in the single-turn return magnetic field enhanced outer coil group is as follows: Therefore, the design method of the distance between the coils in the same group in the single-turn return magnetic field enhanced outer coil group is as follows: (11) wherein is the magnetic field maintenance coefficient, generally taken as 0.95.

[0031] 12) Design of the distance between the adjacent groups of coils in the single-turn return magnetic field enhanced outer coil group (m): As shown in Figure 1 , if the distance between the adjacent groups of coils is too large, a magnetic field valley will appear in the central region. Therefore, the distance between the adjacent groups of coils in the single-turn return magnetic field enhanced outer coil group should be reduced in design, and the minimum value of the alternating magnetic field generated by a single wire at a vertical height of from the wire is taken as the reference value. In order to ensure that the magnetic field between the two adjacent wires is greater than the reference value, a magnetic field superposition coefficient is introduced. To ensure that the magnetic field generated directly above the midpoint of the two adjacent wires is equal to , the magnetic induction intensity thereof is . Therefore, the design method of the distance between the adjacent groups of coils in the single-turn return magnetic field enhanced outer coil group is as follows: Therefore, the design method of the distance between the adjacent groups of coils in the single-turn return magnetic field enhanced outer coil group is as follows: (12) wherein is the magnetic field superposition coefficient, generally taken as 1.05, is the phase angle of the current passing through the return magnetic field enhanced outer coil.

[0032] 13) Design of the resonant capacitance of each group of coils in the single-turn return magnetic field enhanced outer coil (F): Figure 2 ​​​​​​As shown, when the height of the pot changes, the coupling coefficient between the coil and the pot changes, thereby causing the magnetic field strength to attenuate and the equivalent impedance to change, resulting in inconsistent magnetic field distribution at the pot wall. Therefore, by reasonably configuring the resonant capacitance of each group of coils, each group of coils still maintains consistent resonance under different pot height conditions, which is the key to compensating for the attenuation of the magnetic field and maintaining the magnetic field enhancement effect. Based on the coil-pot coupling model and the resonant equivalent circuit model , while keeping the system operating frequency f unchanged, according to the functional relationship between the equivalent inductance of each group of coils and the coupling distance, the corresponding relationship between the resonant capacitance and the geometric parameters and coupling parameters is established, so that the resonant capacitance of each group of coils is enhanced by the single-turn coil C i The design method of the resonant capacitance of each group of coils is as follows: (13) wherein, i is the number of the i-th group of single-turn coil-enhanced outer coils, and the outermost group of coils is 1, k is the shape coefficient of the pot, which can be obtained by measurement, and is 0.04 by default, R i is the corresponding inductive heating coil resistance, which can be obtained by the following formula: (14) Example 5 The present application designs a magnetic field-enhanced outer coil structure with multiple wire single-turn coils, and adopts a power supply mode in which the current directions of adjacent wire groups are opposite, so that the magnetic fields generated by each wire are effectively superimposed, as shown in Figure 6 . Under the action of this magnetic field, eddy currents are generated inside the concave-bottom pot, as shown in Figure 7 , thereby achieving heating of the concave-bottom pot and further increasing the temperature of the side wall of the concave-bottom pot.

[0033] Example 6 The present application uses the finite element software COMSOL to perform electromagnetic-thermal coupling analysis on the designed electromagnetic induction heating coil. The simulation conditions are set as follows: input current 40A, operating frequency 25kHz, concave-bottom pot and flat-bottom pot parameters and geometric dimensions are input according to the actual design values, and the coil conductor is set as a circular hollow copper pipe considering the cooling condition. Through frequency domain simulation calculation under static field, the concave-bottom pot temperature field distribution result shown in Figure 8 is obtained, as shown in the figure, the temperature of the side wall of the concave-bottom pot is about 80℃, which is basically consistent with the temperature of the bottom of the concave-bottom pot, indicating that the designed coil structure can increase the temperature of the side wall of the concave-bottom pot and form a relatively consistent temperature distribution with the bottom. As shown in Figure 9The temperature field distribution result of the flat-bottomed pot is shown. As shown in the figure, the overall temperature distribution of the flat-bottomed pot is relatively uniform, and the temperature difference of each region is small, which indicates that the designed coil structure has good temperature uniformity in the heating process. The results show that the design can realize simultaneous heating of the flat-bottomed pot and the concave-bottomed pot, and improve the temperature of the side wall of the concave-bottomed pot, verifying the feasibility and effectiveness of the application.

Claims

1. An electromagnetic induction heating coil suitable for both flat and concave bottom pans, characterized in that: It includes a single spirally wound inner coil for uniform heating, and several turns of a coiled magnetic field enhancement outer coil are sequentially wound coaxially around the outer side of the inner coil for uniform heating.

2. A design method for an electromagnetic induction heating coil suitable for both flat and concave bottom pans, characterized in that: Including the inner diameter of the single-wire winding uniform heating inner coil A single wire is used to uniformly heat the inner diameter of the inner coil. The radius of cross-section of each layer of conductor in the coil Number of conductor strands N in the coil, and the cross-sectional radius of the coil. d s Single-wire winding for uniform heating, inner coil turn spacing The number of turns of the inner coil for uniform heating by a single wire m The radial distance *s* between the outermost turn of the inner coil for uniform heating with a single conductor and the innermost turn of the outer coil for enhancing the magnetic field; the inner diameter of the outer coil for enhancing the magnetic field. Outer diameter of the rewinding magnetic field enhancement outer coil Spacing between coils in the same group of outer coils for magnetic field enhancement Spacing between adjacent groups of coils in the outer coil of the rewinding magnetic field enhancement coil The resonant capacitance of each group of coils in the outer coil that enhances the magnetic field. The design process.

3. The design method of the electromagnetic induction heating coil for both flat and concave bottom pans according to claim 2, characterized in that: The single-wire coil is used to uniformly heat the inner diameter of the inner coil. The design process is as follows: Considering the distribution of the magnetic field at the center of the inner coil for uniform heating by a single conductor Generating eddy current density inside the cookware This determines the temperature distribution between the center and edge areas of the cookware bottom. A single wire is wound around the inner diameter of the uniformly heated inner coil. The design formula is: (1) in, The permeability of free space, The operating frequency of the induction cooker. The magnetic permeability of the cookware material. The electrical conductivity of the cookware material. Density of cookware material Specific heat capacity of the cookware material; The single-wire coil is used to uniformly heat the inner diameter of the inner coil. The design process is as follows: Based on the equivalent mathematical model of cookware size The magnetic field distribution of the inner coil, which is uniformly heated by a single conductor, is designed to be equivalent to elliptical contour lines. A single wire is used to uniformly heat the inner coil. The design formula is as follows: (2) in, h The height of the concave-bottomed pot. k This is the ratio of the height of the bottom of the pot to the total height of the pot.

4. The design method of the electromagnetic induction heating coil for both flat and concave bottom pans according to claim 2, characterized in that: The radius of each layer of conductor in the coil The design process is as follows: The cross-sectional radius of each layer of wire in the single-conductor-wound uniform heating inner coil and the rewinding magnetic field-enhancing outer coil is... same, The design formula is as follows: (3) in, The inner coil is uniformly heated by a single conductor, and the outer coil material resistivity is enhanced by a wound magnetic field. z For the number of conductor strands z layer; The design process for the number of coil wire strands N is as follows: Since both the inner coil, which is uniformly heated by a single conductor, and the outer coil, which is wound around a magnetic field to enhance the outer magnetic field, contain N strands of conductor, the design formula for the number of conductor strands N is as follows: (4) in, I Design the operating current for the induction cooker. The coefficient of natural heat transfer between the coil and the air; The cross-sectional radius of the coil d s The design process is as follows: The cross-sectional radius of the inner coil, which is uniformly heated by a single conductor, and the outer coil, which is reinforced by a wound magnetic field, are... d s same, d s The design formula is as follows: (5) in, x This represents the number of coil wire layers.

5. The design method of the electromagnetic induction heating coil for both flat and concave bottom pans according to claim 2, characterized in that: The single-wire coil is used to uniformly heat the inner coil turns. The design is as follows: Establish a functional relationship between the turn spacing of the nth coil and the voltage distribution, and uniformly heat the inner coil turns using a single wire. The design formula is: (6) Where n is the value of the nth turn of the coil, and C is Euler's constant; The single-wire winding uniformly heats the inner coil turns. m The design process is as follows: Based on inductor energy storage mechanism Equivalent inductance expression of coil Under the constraint of the correspondence between output power and coil current, a functional relationship between the number of turns m and the power parameter is established, and the number of turns of the inner coil is uniformly heated by a single wire. m The design formula is as follows: (7)。 6. The design method of the electromagnetic induction heating coil for both flat and concave bottom pans according to claim 2, characterized in that: The design process for the radial distance s between the outermost turn of the uniformly heated inner coil and the innermost turn of the outer coil enhanced by the rewinding magnetic field is as follows: Since there is a potential difference between the outermost turn of the uniformly heated inner coil and the innermost turn of the magnetically enhanced outer coil, based on the relationship between the potential difference between the two coils and the air breakdown voltage, and under the constraint that the working voltage difference does not exceed the allowable electric field strength of the air breakdown voltage, the design formula for the radial distance s between the outermost turn of the uniformly heated inner coil and the innermost turn of the magnetically enhanced outer coil is as follows: (8)。 7. The design method of the electromagnetic induction heating coil for both flat and concave bottom pans according to claim 2, characterized in that: The inner diameter of the outer coil for enhancing the rewinding magnetic field The design process is as follows: The inner diameter of the outer coil for enhancing the magnetic field is determined by introducing the coil turn spacing based on the outer diameter of the outer coil for enhancing the magnetic field. The design formula is as follows: (9) Outer diameter of the rewinding magnetic field enhancement outer coil The design process is as follows: The magnetic field distribution within the heating region is equivalent to a hyperbolic model. Establish a rewinding magnetic field to enhance the outer diameter of the outer coil r oo The functional relationship between voltage parameters and cookware dimensions, and the outer diameter of the rewinding magnetic field enhancement coil. r oo The design process is as follows: (10) in, R This refers to the diameter of the pot's opening.

8. The design method of the electromagnetic induction heating coil for both flat and concave bottom pans according to claim 2, characterized in that: The spacing between coils in the same group of the rewinding magnetic field enhancement outer coil The design process is as follows: taking a single conductor at a vertical height of... The maximum value of the alternating magnetic field generated at that location As a reference, a magnetic field maintenance coefficient is introduced to maintain the magnitude of the magnetic field between the two conductors. To ensure that the midpoint of two adjacent wires is directly above The magnetic field generated at that location is equal to Magnetic induction intensity is Therefore, the spacing between coils in the same group of coils in the outer coil is increased by the rewinding magnetic field. The design formula is as follows: (11) in, This is the magnetic field maintenance coefficient.

9. The design method of the electromagnetic induction heating coil for both flat and concave bottom pans according to claim 2, characterized in that: The spacing between adjacent groups of coils of the outer coil with the rewinding magnetic field enhancement The design process is as follows: taking a single conductor at a vertical height of... Minimum value of alternating magnetic field generated at the location To ensure that the magnetic field between the two conductors is greater than the reference value, a magnetic field superposition coefficient is introduced. To ensure that the midpoint of two adjacent wires is directly above The magnetic field generated at that location is equal to Magnetic induction intensity is Therefore, the spacing between adjacent groups of coils in the outer coil is increased by the rewinding magnetic field. The design formula is as follows: (12) in, The magnetic field superposition coefficient is... The phase angle of the current flowing through the outer coil is used to enhance the magnetic field.

10. The design method of the electromagnetic induction heating coil for both flat and concave bottom pans according to claim 2, characterized in that: The resonant capacitance of each group of coils in the outer coil of the revolving magnetic field enhancement coil The design process is as follows: based on the coil-pot coupling model and the resonant equivalent impedance model The resonant capacitance of each group of coils in the outer coil is enhanced by the rewinding magnetic field. The design formula is as follows: (13) in, i For the i-th group of values ​​of the single-turn wound magnetic field enhancement outer coil, k This is the shape coefficient of the cookware. R i The internal resistance of the corresponding induction heating coil is obtained by the following formula: (14)。

Images