Non-resonant electromagnetic induction heating device

Abstract

A non-resonant electromagnetic induction heating device comprises a power supply module providing direct current, a switch module, a one-way conduction type transistor and an inductor module, the one-way conduction type transistor and the inductor module are connected in parallel to form a heating assembly, and the heating assembly and the switch module are connected in series and then connected with the output end of the power supply module; the electromagnetic induction heating device is safe, reliable, low in cost, small in technical difficulty, low in power supply energy consumption and capable of controlling eddy current frequency and power, is a green low-carbon electromagnetic induction heating device, and can be widely applied to hot water preparation, boiled water preparation or food processing in the fields of families and service industry; in the field of industrial application, the device can be used for preparing high-pressure and high-temperature steam, and can be used for heating and smelting materials such as pure metal, alloy and Si and products thereof.

Description

Technical Field

[0001] The utility model relates to the technical field of induction heating, and specifically relates to a non-resonant electromagnetic induction heating device. Background Art

[0002] Induction heating has the characteristics of fast heating speed, high thermal efficiency, and no pollution, and is widely used in daily life and industrial fields, such as induction cookers used in daily life, induction heating heat treatment, welding heating, forging heating, metal melting, etc. in the industrial field. Modern advanced induction heating devices, from induction cookers with a power of only a few hundred watts to metal melting furnaces with hundreds of thousands of megawatts, all invariably use the basic mode of rectification - inversion - resonance, that is, alternating current is changed into direct current through a rectifier bridge, and then combined with a resonance circuit through an inverter bridge to obtain an alternating current similar to a sine wave with a frequency ranging from dozens of hertz to hundreds of thousands of hertz, generating an induction magnetic field with the same frequency in the inductor, and the material in the magnetic field generates eddy currents and is rapidly heated.

[0003] Currently, there are two types of resonance circuits used for induction heating, namely RLC series resonance and RLC parallel resonance. CN202721845U discloses an energy-saving high-power IGBT series resonance type forging induction heating furnace, which uses 4 high-power IGBTs to form an inverter circuit, and there are 7 capacitors in addition to the resonance capacitor connected in series with the inductor. One of the disadvantages of series resonance is that when the current on the inductor is not 0 and the power switch is disconnected, a ripple voltage will appear. When the ripple voltage is severe, it may breakdown the insulation layer of the inductor or breakdown the power switch. Secondly, the AC voltage at both ends of the inductor is more than twice the DC voltage, which poses a certain safety hazard. Parallel resonance overcomes the above two disadvantages of series resonance, but brings problems of ripple current and difficult startup. CN104822186A discloses a startup strategy and its implementation system for a parallel resonance induction heating power supply under heavy load. An additional reactor is added to the DC power supply, which is beneficial to overcoming ripple current, but brings the risk of ripple voltage. Whether it is series resonance or parallel resonance, the "inverter frequency tracking and phase-locking technology" must be used, and this technology is one of the key technologies of induction heating power supplies. CN 109379795B discloses an inverter frequency tracking and phase-locking control system for an induction heating power supply. Although the control problem is solved, the control system is complex and cannot control the frequency size as needed. This is because the frequency f of the resonance circuit is determined by the capacitance value C of the resonance capacitor and the inductance value L of the inductor. The inductor is designed according to the shape and size of the object to be heated. In order to ensure the working frequency range of the load, a capacitor needs to be used to match it. In addition, the large number of capacitors, reactors, and more power switches used in the power supply increase the power supply cost and power loss of the power supply, which is also one of the problems to be improved in current induction heating devices. Summary of the Invention

[0004] To solve the above technical problems, the present utility model provides a non-resonant electromagnetic induction heating device, which is safe and reliable, low in cost, low in technical difficulty, low in power consumption of the power supply, and can control the eddy current frequency and power. It is a green and low-carbon electromagnetic induction heating device, which can be more widely applied to the fields of family and service industry for preparing hot water, boiling water or food processing; in the industrial application field, it can be used to prepare high-pressure and high-temperature steam, and can be used to heat and melt pure metals, alloys, Si and other materials and their products.

[0005] To achieve the above technical purpose, the technical solution adopted is: a non-resonant electromagnetic induction heating device, including a power supply module for providing direct current, a switching module, a unidirectional conduction type transistor and an inductor module. The unidirectional conduction type transistor and the inductor module are connected in parallel to form a heating component, and the heating component is connected in series with the switching module and then connected to the output end of the power supply module.

[0006] Further, the switching module includes, but is not limited to, a gate turn-off thyristor, an insulated gate bipolar transistor, and a metal oxide semiconductor field effect transistor.

[0007] Further, the unidirectional conduction type transistor includes, but is not limited to, a diode and a thyristor.

[0008] Further, the power supply module is a two-phase DC power supply.

[0009] Further, the power supply module is composed of a two-phase AC power supply, a rectifier bridge, a diode, an inductor and a capacitor. The two-phase AC power supply is connected to the input end of the rectifier bridge. The output end of the rectifier bridge and the diode are connected in parallel and then connected in series with the inductor, and then connected in parallel with the capacitor.

[0010] Further, the power supply module is composed of a three-phase AC power supply and a rectifier bridge, and the output end of the three-phase AC power supply is connected to the input end of the rectifier bridge.

[0011] Further, the power supply module is composed of a three-phase AC power supply, a rectifier bridge, a second switching module, a diode, an inductor and a capacitor. The three-phase AC power supply is connected to the input end of the rectifier bridge. The output end of the rectifier bridge is connected in series with the second switching module, then connected in parallel with the diode and then connected in series with the inductor, and then connected in parallel with the capacitor.

[0012] The beneficial effects of the present utility model are:

[0013] 1. The present utility model forms a heating component by connecting a unidirectional conduction type transistor and an inductor module in parallel, realizing that the rate of change of the magnetic field intensity changes synchronously with the magnetic field intensity, thereby improving the electromagnetic conversion efficiency and solving the problem of low electromagnetic conversion rate in the prior art.

[0014] 2. The utility model realizes the arbitrary change of the working frequency of the load according to process requirements by controlling the control period of the switch module, and solves the technical problem that in the prior art, the frequency can only be changed by the matching of capacitors and inductors.

[0015] 3. Compared with the existing resonance technology, the utility model does not require adding capacitors and reactors between the power supply module and the inductor module, and the power switches are also reduced by half. This not only significantly reduces the cost and the volume of the power supply, but also reduces the power loss of the power supply.

[0016] 4. The utility model realizes the technical problem of arbitrarily adjusting the power without increasing the cost.

[0017] 5. The utility model does not have the problem of capacitor boosting, and can more than double the voltage of the direct current on the basis of the prior art, thereby further reducing the loss of the power supply.

[0018] 6. Since a unidirectional conduction type transistor is connected in parallel at both ends of the inductor module in the non-resonant electromagnetic induction heating device of the utility model, and the unidirectional conduction type transistor has a freewheeling function, it solves the problem of high voltage caused by abnormal current change in the inductor in the prior art and improves the safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the circuit principle block diagram of the utility model;

[0020] Figure 2 is the circuit schematic diagram of the heating component formed by the parallel connection of the unidirectional conduction type transistor of the utility model and the inductor module;

[0021] Figure 3 is the schematic diagram of the output voltage waveform and characterization parameters of the non-resonant induction heating device of the utility model;

[0022] Figure 4 is the schematic diagram of the current passing through the RLD non-resonant load of the utility model;

[0023] Figure 5 is the schematic diagram of the current passing through the RLC resonant load in the prior art;

[0024] Figure 6 is the application schematic diagram of the utility model with an induction heating device (heating water and generating steam) connected in series on a water pipe;

[0025] Figure 7 is the circuit schematic diagram of the non-resonant induction heating device powered by two-phase AC 220V of the utility model;

[0026] Figure 8It is a comparison diagram of voltage waveforms after rectification of 50Hz in two-phase 220V AC and three-phase 380V;

[0027] Figure 9 It is a schematic circuit diagram of a non-resonant induction heating device powered by AC 380V of the present invention;

[0028] Figure 10 It is a power supply diagram of using one DC power supply to supply power to multiple non-resonant induction heating devices (medium-frequency melting furnaces) in a foundry workshop;

[0029] Figure 11 It is a schematic circuit diagram of a non-resonant induction heating device with chopper step-down power supply of the present invention.

[0030] Figure 12 It is a schematic circuit diagram of a non-resonant induction heating device powered by DC of the present invention; Specific embodiments

[0031] The present invention will be further described in detail below with reference to the accompanying drawings, theoretical analysis and specific embodiments.

[0032] As Figure 1 shown, a non-resonant electromagnetic induction device of the present invention mainly includes five major modules, namely a power supply module 1, a switching module 2, a unidirectional conduction type transistor 3, an inductor module 4 and a material module 5. The unidirectional conduction type transistor 3 and the inductor module 4 are connected in parallel to form a heating component (RLD non-resonant load). The heating component is used to inductively heat the material module 5. The heating component is connected to the output end of the power supply module 1 after being connected in series with the switching module 2. First, the main problems that should be considered in the implementation process of these five major modules will be described below, and then the control part will be described.

[0033] 1. Power supply module

[0034] The power supply module 1 is a direct current with a relatively stable maximum voltage value and can provide a large enough unidirectional flowing current for one or more non-resonant electromagnetic induction heating devices. The main technical indicators of the power supply module 1 include rated voltage and rated current. The power supply module 1 can adopt a DC power supply or be converted from an AC power supply to DC power supply.

[0035] (1) Rated voltage

[0036] Since a unidirectional conduction type transistor 3 is connected in parallel to the inductor module 4 in the non-resonant electromagnetic induction heating device of the present utility model, when the switch module 2 is turned off, the voltage across the inductor module 4 is equal to the voltage across the unidirectional conduction type transistor 3, and this voltage is only about 1V. When the switch module 2 is turned on, the voltage across the inductor module 4 is equal to the voltage of the DC power supply. Therefore, the highest voltage across the inductor module 4 in the non-resonant electromagnetic induction heating device of the present utility model is the highest voltage of the DC power supply, and this highest voltage is called the rated voltage of the power supply module 1. The basic principle for determining the rated voltage is as follows: First, consider electrical safety and reduce the rated voltage as much as possible; second, consider reducing the energy consumption of the circuit and the switch and increase the rated voltage as much as possible; third, consider the existing power supply conditions and the highest voltage required by the load. Considering comprehensively, it is to increase the rated voltage as much as possible on the premise of the existing power supply conditions being permitted and ensuring safety. The commonly used AC voltages are 220V and 380V, and the DC voltage after full-bridge rectification is thus determined. In the industrial application field, in most cases, three-phase electricity is directly used after full-bridge rectification; in high-power usage scenarios, such as the melting of metals and their alloys or Si, because of the large power, a special transformer is needed to convert the high-voltage AC power into low voltage for use, and it can be converted to the required rated voltage and then used after rectification. In this scenario, the factors determining the rated voltage are mainly the insulation performance of the non-resonant electromagnetic induction heating device and the inductance value of the inductor. In the prior art, the power supply module in induction heating needs to be further filtered, that is, capacitors are connected in parallel and reactors are connected in series after rectification. For the DC power supply system of the non-resonant electromagnetic induction heating device of the present utility model, the circuit after three-phase alternating current is rectified into direct current does not need to be further filtered. Its advantages include: (1) The capacitors and reactors between the power supply module and the inductor module are omitted, reducing the cost; (2) The cooling system for cooling the capacitors and reactors is omitted, thus reducing the cost again; (3) The volume of the power supply cabinet can be significantly reduced, thereby reducing the cost again and the floor area of the control cabinet; (4) The energy consumption of the cooling system for the capacitors and reactors is avoided, which is a low-carbon technical solution. Of course, in some scenarios, such as when an induction heating power supply uses different inductors and the inductance values of different inductors vary greatly and the used power also varies greatly, a DC-DC conversion circuit can be added to adjust the power of the heating component by adjusting the voltage of the power supply module.

[0037] (2) Rated current

[0038] The current of the non-resonant electromagnetic induction heating device of the present utility model is in a proportional relationship with the voltage. Therefore, the effective value and the average value of the DC current are equal, that is, the rated current can be calculated according to the required power.

[0039] (3) Air switch and circuit breaker

[0040] To prevent loss of control, that is, when the switch module cannot cut off the power supply or the unidirectional conduction transistor can conduct in the reverse direction, the current in the non-resonant electromagnetic induction heating device of the present invention will be very large. Therefore, an overcurrent protection device can be added to the device. When an overcurrent occurs, the overcurrent protection device protects the circuit. An air switch or circuit breaker should be used to protect the rectifier bridge from overcurrent between the alternating current and the rectifier bridge; an air switch or circuit breaker should be added between each electromagnetic induction heating device and the DC power supply to protect the electromagnetic induction heating device. An air switch is used for small-power electromagnetic induction heating devices, while a circuit breaker is selected for large-power electromagnetic induction heating devices. The content here is prior art and will not be elaborated further.

[0041] 2. Switch module

[0042] The switch module 2 selects a unidirectional conduction type transistor switch, including but not limited to gate turn-off thyristor (GTO), insulated gate bipolar transistor (IGBT), metal oxide semiconductor field effect transistor (MOSFET), etc. The main technical parameters considered for the switch selection are the breakdown voltage value, operating frequency, power, heat generation, etc. of the switch.

[0043] 3. Unidirectional conduction type transistor

[0044] The unidirectional conduction type transistor, as the unidirectional conduction device in the freewheeling circuit, includes but not limited to diodes (freewheeling diodes), thyristors (SCRs), etc. The advantage of a diode is that it does not require control, and for others, it is necessary to control it to be in the normally open state to replace the diode. In high-power applications, such as large smelting furnaces, placing the unidirectional conduction transistor at the connection terminal of the inductor instead of inside the power supply cabinet can reduce the current in the section from the inductor to the power supply cabinet, with a certain energy-saving effect.

[0045] 4. Inductor module

[0046] The inductor module 4 is an inductor with a relatively large inductance value in the shape of a spiral tube (barrel), planar, curved surface, or other shapes, which is wound by a metal wire or metal tube with good electrical conductivity. Spiral inductors are widely used in intermediate frequency melting furnaces, surface heating and overall heating of cylindrical metals. Planar inductors are widely used in induction heating of induction cookers, flat metals, etc. Inductors can be used in series or in parallel. Since the highest voltage in the non-resonant electromagnetic induction heating device of the present invention is the voltage of the DC power supply, and in the prior art, due to the voltage boosting effect of capacitors, the highest voltage across the inductor is higher than the voltage of the direct current. For example, the peak voltage of series resonance is more than twice the DC voltage. Therefore, when using the technology of the present invention, theoretically, the DC voltage can be increased by more than one time on the existing basis, which is beneficial to reducing the losses of switches and circuits. In the prior art, induction heating power supplies with one-to-two or one-to-three have been widely used. When using the present invention, alternating current can be directly rectified in the substation to supply power to all induction heating devices, and the power cabinet only needs to install a circuit breaker, a switch module, a unidirectional conduction transistor (the unidirectional conduction transistor can also be moved to the inductor), a control board, and other necessary accessory instruments, etc., and its superiority is self-evident.

[0047] When analyzing the circuit, the inductor with an inductance value of L in the inductor module is abstracted as a resistor with an internal resistance value of R, and the heating of the material is realized by the equivalent resistor R W and the inductor with an inductance value of L. The circuit schematic diagram of the heating component formed by the parallel connection of the unidirectional conduction transistor 3 and the inductor module 4, that is, the RLD non-resonant load, is as Figure 2 shown.

[0048] 5. Material module

[0049] The objects of induction heating are collectively referred to as materials. Materials are solids, liquids, or solid + liquid substances with certain magnetic permeability and electrical conductivity and are located inside the spiral tube (barrel) inductor or at the end face of the planar or curved surface inductor. Various metals and their alloys, Si, etc. are commonly used materials, and water can be placed in a metal container and heated or even vaporized by heating the metal container. The material generates eddy current phenomenon and heats up due to the action of the changing magnetic field generated by the inductor module 4, and the mutual inductance voltage generated on the inductor is

[0050]

[0051] The instantaneous power of eddy current heating is:

[0052]

[0053] Where: U WThe mutual inductance voltage or equivalent voltage generated on the inductor due to the heat of the material, and its direction is the same as the current direction; W is called the material coefficient, and its value range is [0, 1). The material coefficient is related to various factors such as the magnetic permeability, conductivity, shape, size, and quantity of the material; L is the inductance value of the inductor; i is the current flowing through the inductor. In the discussions of existing technologies and academic papers, the eddy current load is invariably equivalent to a fixed resistor, which is obviously inconsistent with the inductance characteristics of eddy currents. According to the above analysis, this equivalent resistor is a variable resistor, that is

[0054]

[0055] 6. Control method

[0056] When the DC rectifier bridge and the unidirectional conduction transistor are diodes, they do not require control. When other controllable switches are selected, they are controlled to be normally open. It is mainly the control of the switch module.

[0057] The control method of a non-resonant electromagnetic induction heating device of the present invention includes the following steps:

[0058] Step 1: Set the control period T of the switch module 2;

[0059] Step 2: Set the closing time T of the switch module 2 within a control period on ;

[0060] Step 3: The switch module 2 closes and starts timing;

[0061] Step 4: Maintain the closing time of the switch module 2 as T on and then disconnect;

[0062] Step 5: Delay for T - T on ;

[0063] Step 6: Repeat steps 3 to 5.

[0064] The power control method of the non-resonant electromagnetic induction heating device of the present invention increases the power by increasing the closing time T of the switch module in step 3 of the control method on and decreases the power vice versa.

[0065] The temperature control method of the non-resonant electromagnetic induction heating device of the present invention increases the heating rate of the material module by increasing the closing time T of the switch module in step 3 of the control method on and decreases the heating rate vice versa. When the heating rate is 0, the material maintains a constant temperature state.

[0066] To achieve closed-loop control of power, it is necessary to detect the actual power of the electromagnetic induction heating device as a feedback signal; similarly, to achieve closed-loop control of the material temperature, it is necessary to detect the actual temperature of the material as a feedback signal. There are very mature technologies available for both of these two technologies.

[0067] The working principle of a non-resonant electromagnetic induction heating device is as follows: Alternating current is rectified by a full-bridge rectifier to obtain direct current, or the direct current is directly output from a DC power supply. The direct current is chopped by the switching module 2 and then output as a unidirectional rectangular wave voltage, forming an approximately triangular wave-changing current on the RLD non-resonant load. The changing current generates a changing magnetic field, and eddy currents are generated in the material placed in the changing magnetic field to achieve the purpose of heating the material; the chopping period T of the switching module 2 is set to control the eddy current frequency f of the load; by changing the on-time T of the switching module 2 on Precise control of the material temperature or the output current or power of the power supply module 1 is achieved.

[0068] The switching module 2 is used to make the power output terminal a DC rectangular wave voltage type power supply, and the schematic diagram of its output voltage waveform is as Figure 3 shown, where: U is the height (voltage) of the rectangular wave (volt), T is the period of the rectangular wave (second), and T on is the width of the rectangular wave (second).

[0069] The working principle of the RLD non-resonant load is as follows: When the switching module 2 is turned on, a DC voltage U is applied across the load. Let the current passing through the inductor be i, then

[0070]

[0071] And when the switching module 2 is turned off, the RLD forms a discharge circuit, and its equation is

[0072]

[0073] where: R is the resistance in the circuit, W is the material coefficient, and L is the inductance value of the inductor module.

[0074] From Equation (2) and Equation (3), it can be obtained that the current passing through the load is approximately a triangular wave, as Figure 4 shown. When the voltage is constant, T on = 0.5T, the eddy current heating power is the largest. Therefore, usually T on should be less than 0.5T.

[0075] When induction heating is used in the industrial field to heat metals and their parts, due to the skin effect of eddy currents, higher requirements are placed on the frequency f of the eddy currents. For example, in surface quenching, if the required hardened layer is shallower, the required frequency is higher, while forging heating requires a lower frequency. For induction heating melting furnaces, the larger the melting furnace volume, the lower the required frequency. In series resonance and parallel resonance, the current passing through the induction heater is a sine wave type, such as Figure 5 As shown, the relationship between the frequency f and the period T is f = 1 / T. Figure 4 The period T in is equivalent to Figure 5 Therefore, the relationship between the frequency f of the eddy current and the period T of the switch module 2 is:

[0076]

[0077] The method for controlling the material eddy current frequency f of the non-resonant electromagnetic induction heating device of the utility model is: setting the period T of the switch module 2 to:

[0078] The following will further explain the relevant issues based on different application scenarios.

[0079] The typical application of induction heating in the fields of home and catering is heating water. Electromagnetic induction heating cannot directly heat water. The principle of heating water is to heat the metal container through electromagnetic induction, and the metal container then heats the water inside it. The induction cooker currently used in restaurants and homes is a typical application case. Another case that needs further development is to directly connect an electromagnetic induction heating device in series with the water pipe to heat the water or prepare it into steam, such as Figure 6 As shown. The electromagnetic induction heating device is directly connected in series to the water pipe to control the temperature of the water pipe to achieve the purpose of controlling the outlet water temperature. Since electromagnetic induction heating is fast and the water pipe itself is heated, there is no thermal lag problem (thermal lag problem exists when using resistance heating or gas heating), and it is easy to control the water temperature at a constant temperature. If used in homes and hotels, it can replace the current hot water pipes and their heating systems. When steam is prepared, it can be used to steam buns, steamed dumplings, steamed rice, etc. In these applications, the power supply is generally a two-phase AC 220V, which needs to be rectified by a full bridge and then filtered by a diode D7, an inductor L1 and a capacitor C as a DC power supply module 1, such as Figure 7 After the full bridge rectifier D1~D4, the AC 220V becomes a 2-pulse DC power with a voltage waveform as shown in the figure. Figure 8 As shown in the figure, if no filtering is performed, the effective value of the voltage is still 220V. Since the load is an inductive load, the power factor is small. After filtering by D7, L1, and C, the effective value of the voltage is increased and the power factor is improved. When the two-phase DC power supply is used as a power supply module, no additional components are required. The specific circuit is as follows: Figure 12 shown.

[0080] In the field of industrial applications, the commonly used alternating current is 380V three-phase power, which is rectified by a full bridge to obtain 6-pulse direct current. The voltage waveform is as Figure 8 shown. The effective value of the voltage has reached 510V. Even if the load is an inductive load, the power factor is relatively high, so there is no need for further filtering. The 380V three-phase alternating current is rectified by the full bridge of D1 - D6 as the power supply, as Figure 9 shown.

[0081] From Equation (2) and Equation (3), the calculation formula for the average output power of the DC power supply of the non-resonant electromagnetic induction heating device of the present invention can be obtained as

[0082]

[0083] It can be seen that the load power is determined by various factors such as the output voltage U of the power supply module 1, the conduction time T on of the switch module 2 and the control period T, the resistance value R, the inductance value L, and the material coefficient W of the inductor module 4. It is not difficult to prove that as R, L, and W increase, the power decreases. In practice, it is desired to reduce R because R causes the circuit to heat up and wastes electrical energy, but in order to increase L, R also increases accordingly. After U, R, L, and W are determined, T on and T, especially η = T on / T become the control parameters for controlling the power output of the power supply. However, since T on / T ≤ 0.5, that is, when T on / T = 0.5, the power is the largest. Then the problem arises that this maximum power, that is, the rated power, may not necessarily meet the requirements. When it cannot be met, there are two ways to solve it: First, by changing the design of the load, that is, changing R, L, and W to meet the requirements, which is a relatively economical and practical method; second, by changing the output voltage U of the power supply module 1, which will increase the power supply cost. Two application examples of changing the voltage are given below.

[0084] In modern foundry workshops, one power supply for two, that is, one power supply supplies power to two intermediate frequency melting furnaces at the same time. One of the melting furnaces is in the melting or heating-up stage (with large power consumption) while the other is in the heat preservation stage (with small power consumption), which has been widely applied. And in a foundry workshop, there are often multiple melting furnaces. With the existing technology, it can only achieve one power supply for two or one power supply for three. Applying the non-resonant electromagnetic induction heating technology, it can be Figure 10The overall design is carried out according to the shown scheme. The AC high voltage is directly rectified after being transformed by a transformer (to obtain the required voltage, usually several hundred volts to several thousand volts), and the rectified direct current is sent to the control cabinets of each intermediate frequency melting furnace. A circuit breaker, a switch module and a unidirectional conduction transistor are installed in the control cabinet. If conditions permit, the unidirectional conduction transistor can also be installed at the inductor connection. This will significantly reduce the electrical loss of the line and the power supply cost.

[0085] Induction heating surface hardening is one of the main processes for heat treatment of metal parts. It has relatively high requirements for the eddy current frequency f. For different parts, the requirements for the eddy current frequency f value, power size, etc. also vary greatly, and the R and L of the inductor also vary greatly. Existing resonance technologies all achieve that the eddy current frequency f works within a certain range through the matching of the resonance capacitor and the inductor. By using the non-resonant induction heating technology of the present utility model, a non-resonant induction heating device with chopper step-down power supply can be used to meet the above requirements. Determine the operating frequency of the switch module 2 according to the requirements for the eddy current frequency. When the frequency requirement is high (such as greater than 30 kHz), an insulated gate field effect transistor is selected as the switch, and the power is controlled by adjusting the voltage and the duty cycle of the switch module 2, which has greater flexibility and adaptability. Figure 11 ​

Claims

1. A non-resonant electromagnetic induction heating device, characterized in that: The invention comprises a power supply module (1) for providing direct current, a switch module (2), a unidirectional conductive transistor (3) and an inductor module (4); the unidirectional conductive transistor (3) and the inductor module (4) are connected in parallel to form a heating component; the heating component is connected in series with the switch module (2) and then connected to the output end of the power supply module (1).

2. A non-resonant electromagnetic induction heating device as claimed in claim 1, characterized in that: The switch module (2) includes but is not limited to a gate turn-off thyristor, an insulated gate bipolar transistor, and a metal oxide semiconductor field effect transistor.

3. A non-resonant electromagnetic induction heating device as claimed in claim 1, characterized in that: The unidirectional conducting transistor (3) includes but is not limited to a diode and a thyristor.

4. A non-resonant electromagnetic induction heating device as claimed in claim 1, characterized in that: The power supply module (1) is a two-phase DC power supply.

5. A non-resonant electromagnetic induction heating device as claimed in claim 1, characterized in that: The power supply module (1) is composed of a two-phase AC power supply, a rectifier bridge, a diode (D7), an inductor (L1) and a capacitor (C). The two-phase AC power supply is connected to the input end of the rectifier bridge, and the output end of the rectifier bridge is connected in parallel with the diode (D7), then in series with the inductor (L1), and then in parallel with the capacitor (C).

6. A non-resonant electromagnetic induction heating device as claimed in claim 1, characterized in that: The power supply module (1) is composed of a three-phase AC power supply and a rectifier bridge, and the output end of the three-phase AC power supply is connected to the input end of the rectifier bridge.

7. A non-resonant electromagnetic induction heating device as claimed in claim 1, characterized in that: The power supply module (1) is composed of a three-phase AC power supply, a rectifier bridge, a second switch module (G1), a diode (D7), an inductor (L1) and a capacitor (C). The three-phase AC power supply is connected to the input end of the rectifier bridge, and the output end of the rectifier bridge is connected in series with the second switch module (G1), then in parallel with the diode (D7), then in series with the inductor (L1), and then in parallel with the capacitor (C).

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