Induction heating system based on adjustable impedance relay coil

Abstract

The invention discloses an induction heating system based on an adjustable impedance relay coil. The induction heating system comprises a power source module, a transmitting coil module, a relay coil module and an equivalent eddy current load, the power source module comprises an alternating current voltage source which is connected with the transmitting coil module; the transmitting coil module is formed by sequentially connecting a transmitting coil compensation capacitor, a transmitting coil internal resistor and a transmitting coil inductor in series; the relay coil module comprises a capacitor switching matrix, a relay coil inductor, a relay coil compensation capacitor and a relay coil internal resistor, wherein the relay coil inductor, the relay coil compensation capacitor and the relay coil internal resistor are sequentially connected in series. The capacitor switching matrix is connected with the relay coil compensation capacitor in parallel. The equivalent eddy current load comprises a load equivalent inductor and a load equivalent resistor which are connected in series; the transmitting coil module transmits energy to the repeating coil module through magnetic coupling; the repeating coil module transmits energy to the equivalent eddy current load through magnetic coupling; the surface of the equivalent eddy current load excites induced eddy current, and electric energy is converted into heat energy. The heating uniformity can be remarkably improved, and the power adjusting range can be widened.

Description

Technical Field

[0001] This invention relates to the technical field of induction heating, and in particular to an induction heating system based on an adjustable impedance relay coil. Background Technology

[0002] Induction heating technology is widely used in modern home cooking and industrial heat treatment due to its high efficiency, cleanliness, and fast heating speed. Currently, the most common induction heating system uses a single-coil structure, where an inverter drives a single transmitting coil to generate a high-frequency alternating magnetic field, thereby inducing eddy currents at the bottom of the equivalent eddy current load for heating. However, this single-coil system has significant limitations: First, the uneven distribution of eddy currents on the surface of the equivalent eddy current load causes the heating area to often concentrate at the center of the equivalent eddy current load, resulting in a "hot spot" phenomenon that affects heating efficiency and safety. Second, the adjustment of the system's output power usually depends on changing the inverter's operating frequency or DC bus voltage, which is inflexible and may affect the system's resonant state, leading to a decrease in efficiency.

[0003] To address these issues, the industry has attempted to introduce repeater resonators to improve magnetic field distribution. However, most repeaters in existing technologies have fixed parameters, and their impedance characteristics cannot be changed once installed. This makes it difficult to adaptively adjust them according to different equivalent eddy current loads, power requirements, or heating modes, and thus cannot simultaneously optimize heating uniformity and power adjustment flexibility. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing single-coil induction heating systems, such as poor heating uniformity and inconvenient output power adjustment. This invention proposes an induction heating system based on an adjustable impedance relay coil. By introducing an adjustable impedance relay coil module, this system can actively control the magnetic field distribution on the surface of the equivalent eddy current load and the system's transmission power, thereby significantly improving heating uniformity and widening the power adjustment range.

[0005] To achieve the above objectives, the technical solution provided by the present invention is: an induction heating system based on an adjustable impedance relay coil, comprising a power source module, a transmitting coil module, a relay coil module, and an equivalent eddy current load;

[0006] The power source module includes an AC voltage source, which is directly connected to the transmitting coil module to provide power to the transmitting coil module, the relay coil module and the equivalent eddy current load.

[0007] The transmitting coil module is a series resonant network consisting of a transmitting coil compensation capacitor, a transmitting coil internal resistance, and a transmitting coil inductance connected in series.

[0008] The relay coil module includes a relay coil internal resistance, a relay coil inductance, a relay coil compensation capacitor, and a capacitor switching matrix. The relay coil inductance, the relay coil compensation capacitor, and the relay coil internal resistance are connected in series. The capacitor switching matrix is ​​connected in parallel with the relay coil compensation capacitor to dynamically adjust the equivalent impedance of the relay coil module.

[0009] The equivalent eddy current load includes a load equivalent inductance and a load equivalent resistance connected in series;

[0010] The transmitting coil module transmits energy to the relay coil module via magnetic coupling; the relay coil module transmits energy to the equivalent eddy current load via magnetic coupling; induced eddy currents are excited on the surface of the equivalent eddy current load, thereby converting electrical energy into heat energy.

[0011] Preferably, by adjusting the equivalent impedance of the relay coil module, the amplitude of the current in the relay coil module and its phase relationship with the current in the transmitting coil module are changed, thereby adjusting the output power of the system and changing the magnetic field distribution on the load surface to adjust the heating uniformity of the equivalent eddy current load.

[0012] Preferably, the input impedance as viewed from the transmitting coil module side Represented as:

[0013] ;

[0014] In the formula, The self-impedance of the transmitting coil module satisfies , This is the internal resistance value of the transmitting coil. To compensate for the capacitance value of the transmitting coil, This is the inductance value of the transmitting coil. The imaginary unit, Let be the angular frequency, satisfying , This refers to the system's operating frequency. The self-impedance of the relay coil module satisfies , This is the internal resistance value of the relay coil. This is the inductance value of the relay coil. This is the value of the relay coil compensation capacitor; The equivalent impedance of the equivalent eddy current load satisfies , This is the equivalent resistance value of the load. This is the equivalent inductance value of the load; This refers to the mutual inductance value between the transmitting coil module and the relay coil module; This is the mutual inductance value between the relay coil module and the equivalent eddy current load; This is the mutual inductance value between the transmitting coil module and the equivalent eddy current load.

[0015] Preferably, the compensation capacitors for the transmitting coil and the relay coil in the system are designed to compensate for the inductance of the corresponding coils, so that the system resonates at a specific frequency, the resonant frequency being... Represented as: The resonance condition occurs when the applied operating frequency equals the resonant frequency. At that time, the combined impedance of the transmitting coil module and the relay coil module is purely resistive;

[0016] Based on the above resonance condition, the eddy currents induced in the equivalent eddy current load can be derived. The expression is: ,in The voltage of the AC voltage source; the output power of the system. That is, the Joule heat loss generated by induced eddy currents in the equivalent eddy current load, expressed as: .

[0017] Preferably, the adjustment of the equivalent impedance of the relay coil module is achieved by changing the capacitance value of the relay coil compensation capacitor, and the change of the capacitance value is controlled by the capacitor switching matrix.

[0018] Preferably, the control power of the capacitor switching matrix is ​​provided by a self-powered energy harvesting module. The input terminal of the self-powered energy harvesting module is connected to the relay coil module, and the voltage induced by the relay coil module in the alternating magnetic field is used as the energy source to directly drive the capacitor switching matrix.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] 1. This invention introduces a capacitor switching matrix into the relay coil module, enabling users to flexibly adjust the output power amplitude of the system and effectively improve the heating uniformity of the equivalent eddy current load surface.

[0021] 2. The capacitor switching matrix adopts a self-powered design, which improves the system's integration and reliability.

[0022] 3. This invention effectively overcomes the shortcomings of traditional single-coil heating methods, such as concentrated heat field and inconvenient power adjustment, and innovatively solves the industry problems of inconvenient power adjustment and poor heating uniformity in traditional induction heating systems. Its core advantage lies in the use of a capacitor switching matrix connected in parallel with the relay coil compensation capacitor, which allows for flexible adjustment of the coil impedance, thereby precisely controlling the magnetic field distribution, significantly expanding the uniform heating area at the bottom of the equivalent eddy current load, and achieving wide-range, high-precision power output. Simultaneously, the unique self-powered energy harvesting module utilizes the induced electrical energy of the relay coil module to drive the capacitor switching matrix, eliminating the need for external power supply. This simplifies the structure, reduces costs, and greatly improves the system's reliability and energy efficiency. Ultimately, this design significantly improves the system's heating uniformity, control freedom, equivalent eddy current load compatibility, and overall energy efficiency, demonstrating outstanding comprehensive advantages. Attached Figure Description

[0023] Figure 1 This is the equivalent circuit diagram of the system of the present invention.

[0024] Figure 2 This is a simplified equivalent circuit diagram of the system of the present invention.

[0025] Figure 3a The graph shows the relationship between input power and compensation capacitor (capacitance value between 1 and 10uF).

[0026] Figure 3b Input power varies with compensation capacitor (capacitance value is 10). -2 ~10 4 The relationship between the changes of uf is shown in the graph.

[0027] Figure 4 This shows the relationship between the effective value of the relay coil module current and the change of the compensation capacitor.

[0028] Figure 5a This is a cloud map showing the induced current density distribution on the equivalent eddy current load surface without the addition of a relay coil module.

[0029] Figure 5b This is a cloud map showing the induced current density distribution on the equivalent eddy current load surface under different phase conditions after adding the relay coil module. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0031] like Figure 1As shown, this embodiment discloses an induction heating system based on an adjustable impedance relay coil, including a power source module, a transmitting coil module I, a relay coil module II, and an equivalent eddy current load III. The power source module includes an AC voltage source, which is directly connected to the transmitting coil module I to provide electrical energy to the transmitting coil module I, the relay coil module II, and the equivalent eddy current load III. The transmitting coil module I is a transmitting coil compensation capacitor. Internal resistance of transmitting coil and transmitting coil inductance A series resonant network formed by connecting the relay coils sequentially; the relay coil module II includes the internal resistance of the relay coil. , relay coil inductance , relay coil compensation capacitor and the capacitor switching matrix, the relay coil inductor , relay coil compensation capacitor With the internal resistance of the relay coil The capacitor switching matrix and the relay coil compensation capacitor are connected in series. Parallel connection is used to dynamically adjust the equivalent impedance of relay coil module II; the equivalent eddy current load (III) includes the load equivalent inductance connected in series. and load equivalent resistance The transmitting coil module I transmits energy to the relay coil module II via magnetic coupling; the relay coil module II transmits energy to the equivalent eddy current load III via magnetic coupling; the equivalent eddy current load III converts the transmitted electrical energy into heat energy through induction heating.

[0032] Based on the above induction heating system, the input impedance of the system's transmitting coil module It can be represented as:

[0033] ;

[0034] In the formula, The self-impedance of transmitting coil module I satisfies , This is the internal resistance value of the transmitting coil. To compensate for the capacitance value of the transmitting coil, This is the inductance value of the transmitting coil. The imaginary unit, Let be the angular frequency, satisfying , This refers to the system's operating frequency. The self-impedance of relay coil module II satisfies , This is the internal resistance value of the relay coil. This is the inductance value of the relay coil. This is the value of the relay coil compensation capacitor; The equivalent impedance of the equivalent eddy current load III satisfies... , This is the equivalent resistance value of the load. This is the equivalent inductance value of the load; This refers to the mutual inductance value between transmitting coil module I and relay coil module II; This is the mutual inductance value between relay coil module II and equivalent eddy current load III; This is the mutual inductance value between transmitting coil module I and equivalent eddy current load III.

[0035] The specific steps of this system design method are as follows: Given the input voltage amplitude Operating frequency The self-impedance of transmitting coil module I without equivalent eddy current load was measured experimentally. Self-impedance of relay coil module II without equivalent eddy current load Self-impedance of transmitting coil module I with equivalent eddy current load Self-impedance of relay coil module II with equivalent eddy current load Under the following conditions:

[0036] 1) First, calculate the mutual inductance parameters between the coils based on the impedance change. According to circuit theory, the impedance change and mutual inductance reactance satisfy the following relationship: and ,in, Let be the equivalent impedance of the equivalent eddy current load Ⅲ. By solving the above equations, the two key mutual inductance values ​​can be accurately obtained. and .

[0037] 2) Equivalent circuit modeling and parameter substitution: Since the impedance of the equivalent eddy current load III cannot be directly measured, the source circuit diagram of the system can be simplified to the equivalent circuit diagram shown in Figure 2. Therefore, substituting the relationship in step 1) into the calculation can yield the transformation ratio. This equivalent circuit clearly illustrates the system's energy transfer path: the transmitter-side circuit includes an AC voltage source. And equivalent impedance, the relay-side circuit includes an adjustable capacitor. And the corresponding impedance, the two are mutually inducted To achieve coupling. The defined transformation ratio... It reflects the energy conversion characteristics of relay coil module II and is an important parameter for analyzing the system's transmission efficiency.

[0038] 3) Circuit Analysis and Controllable Parameter Optimization: Based on the simplified equivalent circuit diagram shown in Figure 2, Kirchhoff's Voltage Law (KVL) is written for both the primary and secondary circuits, constructing a complete set of circuit equations. By solving this set of circuit equations, the transmitting coil current can be accurately calculated. and relay coil current The amplitude, phase, and phase difference between the two.

[0039] By systematically changing the adjustable capacitor in relay coil module II Analyze the value of and its impact on the system's operating state: Adjustment The resonant characteristics of relay coil module II can be altered, thereby controlling the amount of transmitted power; simultaneously, changes in capacitance value affect the current. and The phase relationship between the phases is then used to optimize the uniformity of the magnetic field distribution on the surface of the equivalent eddy current load III. Through this active adjustment mechanism, the overall goal of maintaining high-efficiency power transmission and uniform heating under a wide range of load conditions is ultimately achieved.

[0040] Following the design steps above, an example of an induction heating system based on an adjustable impedance relay coil is presented. Given: Input voltage amplitude... Operating frequency Self-impedance of the transmitting coil module without equivalent eddy current load Self-impedance of relay coil module without equivalent eddy current load Self-impedance of the transmitting coil module under load Self-impedance of relay coil module under load According to the design steps, it can be calculated that .

[0041] Based on the above parameters, the relationship between the capacitance and power of the variable capacitor in the relay coil module, the current in the relay coil module, and the heating uniformity is simulated and verified. Figure 3a and Figure 3b The values ​​of the relay coil compensation capacitors are shown respectively. and The simulation results show that the system input power exhibits a significant nonlinear characteristic as the compensation capacitor value changes within a certain range. The maximum value is obtained at (). By adjusting the value of the compensation capacitor, the input power can be adjusted to achieve the desired value. The effective regulation within the range verified that the system has the characteristic of achieving power control through impedance regulation.

[0042] Figure 4This reflects the relationship between the effective value of the relay coil module current and the change in compensation capacitor. Data shows that the relay coil module current varies with the capacitance value... To reach peak .at the same time, Figure 3b The phase difference shown ( The curve shows that the system's operating state transitions between the capacitive and inductive regions as the capacitance value changes, providing a theoretical basis for optimizing heating uniformity through phase modulation.

[0043] Table 1 System Coil Parameters

[0044]

[0045] Table 2 System Electromagnetic Attributes

[0046]

[0047] Based on the system parameters set in Tables 1 and 2, the correlation between the relay coil current characteristics and the induced current density distribution on the surface of the equivalent eddy current load was verified by simulation. Figure 5a and Figure 5b The images show the results without and with the repeater coil module, under different phase differences. , , , The induced current density distribution cloud map of the equivalent eddy current load surface under the condition of ).

[0048] Simulation results clearly show that in the traditional structure without the introduction of a relay coil module, the induced current density distribution on the surface of the equivalent eddy current load is extremely uneven, exhibiting a significant central concentration effect. That is, the current density in the central region of the equivalent eddy current load is significantly higher than that in the edge region. This current distribution characteristic directly leads to excessively high temperatures at the center of the equivalent eddy current load during heating, forming "hot spots," while the edge region is underheated, affecting heating uniformity and performance.

[0049] After introducing the relay coil module, the current density distribution on the equivalent eddy current load surface was significantly improved. By adjusting the current phase difference between the relay coil module and the transmitting coil module, the magnetic field distribution pattern can be effectively controlled. Figure 5b As shown, under different phase difference conditions, the current density distribution is more uniform than that without the relay coil module, the current concentration phenomenon in the central region is effectively suppressed, and the thermal field distribution range is expanded. This result verifies that the proposed relay coil module structure can optimize the electromagnetic energy transfer path through a phase modulation mechanism, thereby achieving a more uniform induction heating effect on the equivalent eddy current load surface.

[0050] In summary, the simulation results validated the effectiveness and advancement of the proposed system from multiple dimensions. At the circuit model level, the simulation results clearly demonstrate that adjusting the compensation capacitor value of the relay coil module can directly change the amplitude and phase relationship of the relay coil module loop current, thereby achieving effective control of the system's transmitted power. This provides theoretical support and practical basis for power control strategies based on impedance matching. At the electromagnetic field and energy distribution level, the current density simulation results further reveal the key role of the relay coil module structure in improving heating uniformity. By optimizing the magnetic field distribution, it significantly improves the uniformity of the induced eddy current distribution on the equivalent eddy current load surface. The above simulation conclusions, from the two key dimensions of system characteristics and output performance, together constitute a complete verification of the core mechanism of this invention, laying a solid data foundation for system parameter optimization and control strategy design, and have important guiding significance.

[0051] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An induction heating system based on an adjustable impedance relay coil, characterized in that, It includes a power source module, a transmitting coil module (Ⅰ), a relay coil module (Ⅱ), and an equivalent eddy current load (Ⅲ); The power source module includes an AC voltage source, which is directly connected to the transmitting coil module (Ⅰ) to provide electrical energy to the transmitting coil module (Ⅰ), the relay coil module (Ⅱ) and the equivalent eddy current load (Ⅲ); The transmitting coil module (Ⅰ) is composed of a transmitting coil compensation capacitor ( ), transmitting coil internal resistance ( ) and transmitting coil inductance ( A series resonant network formed by connecting these components sequentially. The relay coil module (II) includes the relay coil internal resistance ( ), relay coil inductance ( ), relay coil compensation capacitor ( ) and capacitor switching matrix, the relay coil inductance ( ), relay coil compensation capacitor ( ) and the internal resistance of the relay coil ( The capacitor switching matrix and the relay coil compensation capacitor are connected in series. () are connected in parallel to dynamically adjust the equivalent impedance of the relay coil module (Ⅱ); The equivalent eddy current load (Ⅲ) includes the load equivalent inductance connected in series ( ) and load equivalent resistance ( ); The transmitting coil module (Ⅰ) transmits energy to the relay coil module (Ⅱ) through magnetic coupling; the relay coil module (Ⅱ) transmits energy to the equivalent eddy current load (Ⅲ) through magnetic coupling; induced eddy currents are excited on the surface of the equivalent eddy current load (Ⅲ), thereby converting electrical energy into heat energy.

2. The induction heating system based on an adjustable impedance relay coil according to claim 1, characterized in that, By adjusting the equivalent impedance of the relay coil module (II), the amplitude of the current in the relay coil module (II) and its phase relationship with the current in the transmitting coil module (I) are changed, thereby adjusting the output power of the system and changing the magnetic field distribution on the load surface to adjust the heating uniformity of the equivalent eddy current load (III).

3. The induction heating system based on an adjustable impedance relay coil according to claim 1, characterized in that, Input impedance as viewed from the transmitting coil module (Ⅰ) side Represented as: ； In the formula, The self-impedance of the transmitting coil module (Ⅰ) satisfies , This is the internal resistance value of the transmitting coil. To compensate for the capacitance value of the transmitting coil, This is the inductance value of the transmitting coil. The imaginary unit, Let be the angular frequency, satisfying , This refers to the system's operating frequency. The self-impedance of the relay coil module (Ⅱ) satisfies , This is the internal resistance value of the relay coil. This is the inductance value of the relay coil. This is the value of the relay coil compensation capacitor; The equivalent impedance of the equivalent eddy current load (Ⅲ) satisfies , This is the equivalent resistance value of the load. This is the equivalent inductance value of the load; The mutual inductance value between the transmitting coil module (Ⅰ) and the relay coil module (Ⅱ); The mutual inductance value between the relay coil module (Ⅱ) and the equivalent eddy current load (Ⅲ); The mutual inductance value between the transmitting coil module (Ⅰ) and the equivalent eddy current load (Ⅲ) is given.

4. The induction heating system based on an adjustable impedance relay coil according to claim 3, characterized in that, The system's transmitting coil compensation capacitor ( ) and relay coil compensation capacitor ( It is designed to compensate for the inductance of the corresponding coil, so that the system resonates at a specific frequency, the resonant frequency. Represented as: The resonance condition occurs when the applied operating frequency equals the resonant frequency. At that time, the combined impedance of the transmitting coil module (Ⅰ) and the relay coil module (Ⅱ) is purely resistive; Based on the above resonance conditions, the eddy currents induced in the equivalent eddy current load (Ⅲ) can be derived. The expression is: ,in The voltage of the AC voltage source; the output power of the system. That is, the Joule heat loss generated by induced eddy currents in the equivalent eddy current load (Ⅲ) is expressed as: .

5. An induction heating system based on an adjustable impedance relay coil according to claim 1, characterized in that, The adjustment of the equivalent impedance of the relay coil module (II) is achieved by changing the compensation capacitor of the relay coil (II). The capacitance value is achieved by controlling the change of the capacitance value using a capacitor switching matrix.

6. The induction heating system based on an adjustable impedance relay coil according to claim 5, characterized in that, The control power of the capacitor switching matrix is ​​provided by a self-powered energy harvesting module. The input end of the self-powered energy harvesting module is connected to the relay coil module (II). The voltage induced by the relay coil module (II) in the alternating magnetic field is used as the energy source to directly drive the capacitor switching matrix.

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