Induction heating method and device
Patent Information
- Authority / Receiving Office
- KR · KR
- Patent Type
- Patents
- Current Assignee / Owner
- EDWARDS LTD
- Filing Date
- 2020-04-07
- Publication Date
- 2026-08-03
- Estimated Expiration
- Not applicable · inactive patent
Smart Images
Figure 112021115035563-PCT00003_ABST
Abstract
Description
Technology Field
[0001] The present disclosure relates to an induction heating method and apparatus. An aspect of the present invention relates to an induction heating system; an induction heating controller; a component comprising an induction heating element; and a method for heating the component by induction heating. Background Technology
[0002] It is known that in industrial processes, for example, in vacuum systems, temperature management systems (TMS) are utilized to heat pipelines, flanges, valves, and other components. Known TMSs traditionally use resistive heaters, which are strapped onto conduits or other components to raise their temperature. Heat transfer occurs primarily through conduction from the resistive heaters to the conduits or components. This type of TMS is common in semiconductor vacuum processing and other process industries. Heat is used to help reduce or prevent condensation in costly or service-impeding areas of the system, or to aid in the sublimation of materials. However, known TMSs and resistive heaters have certain limitations. For example, they can cause temperature non-uniformity, leading to cold spots that ultimately determine the mean-time between service (MTBS). Other important factors are thermal efficiency and overall temperature, which drive the cost of ownership (for new processes, there is a tendency toward higher temperatures greater than 150°C). Other important factors include cost, reliability, ease of diagnosing heater problems / failures, and simplicity of installation.
[0003] The objective of the present invention is to solve one or more of the disadvantages associated with the prior art.
[0004] Aspects and embodiments of the present invention provide an induction heating system as claimed in the appended claims; an induction heating controller; components; and a method.
[0005] According to an embodiment of the present invention, an induction heating system for heating a component is provided, and the induction heating system is:
[0006] At least one guiding element for positioning close to the outside of the component;
[0007] At least one power module for outputting alternating current to at least one inductive element; and
[0008] It includes a controller configured to identify at least one resonant frequency of alternating current supplied to at least one induction element;
[0009] The controller is configured to determine the operating temperature of the component based on at least one identified resonant frequency. In use, the alternating current supplied to at least one induction element generates an alternating magnetic field to generate current within the component to perform heating. The controller can determine the temperature of the component by monitoring the current supplied to at least one induction element. In at least a given embodiment, the operating temperature of the component can be monitored without the need for a separate temperature sensor.
[0010] The controller is configured to control the supply frequency of the alternating current output to at least one induction element. The controller may be configured to control the operation of at least one power module, for example, to control the frequency of the alternating current output to at least one induction element. The induction heating system according to the present invention generates an alternating electromagnetic field to generate heat directly in the component.
[0011] In at least certain embodiments, induction heating of a component can provide improved efficiency because less power is required to generate a certain amount of heat, particularly at higher temperature / heat input rates. Certain embodiments of an induction heating system are believed to provide improved reliability because the induction element may be less prone to damage, for example, during maintenance. The induction heating system can provide improved uniformity of heating, for example, when several zones or areas are heated from a common controller. The induction heating system is envisioned to be capable of generating high temperatures, for example, 200°C or higher. Since the induction element does not need to be in contact with the component, achieving uniform heating / temperature may be simpler, for at least certain embodiments, for example, when the component has a complex geometric shape. The heating of the component is relatively insensitive to the size of the induction element or the gap between each induction element and the component. It may also be possible to eliminate the need for separate temperature monitoring means, such as sensors or sensors, which can significantly increase cost and complexity, especially during installation.
[0012] The controller may be configured to identify at least one resonant frequency of the alternating current supplied to at least one induction element. By identifying at least one resonant frequency, the controller may selectively control the transmission of power to perform heating of the component.
[0013] The controller may be configured to control the power module to change the supply frequency of the alternating current. The controller may measure the current across at least one inductive element as a function of the supply frequency. The controller may control the power module to implement substantially continuous or incremental (stepped) changes in the supply frequency.
[0014] The controller may be configured to monitor changes in the measured current that depend on changes in the supply frequency of the alternating current. The controller may be configured to identify at least one peak in the measured current. The peak or each peak may include an increase or spike in the measured current. The peak or each peak may be associated with a distinct subset or region of the supply frequency. The controller may identify at least one resonant frequency corresponding to the peak or each peak in the measured current. Identifying at least one resonant frequency may include identifying one or more supply frequencies of the alternating current corresponding to the peak or each peak in the measured current. Each supply frequency causing a peak in the measured current may represent a resonant inductive coupling. The resonant inductive coupling or each resonant inductive coupling is established between the inductive element or between each inductive element and the component. Resonance results in a reduction in the phase shift between the current and the applied voltage, leading to a decrease in circuit impedance, which in turn leads to an increase in the current across at least one inductive element. Power transfer to the component increases at the resonant frequency.
[0015] The controller may be configured to identify peaks detected in the measured current or one or more supply frequencies of the power module corresponding to each peak. Each peak may correspond to a distinct resonant frequency, for example, when more than one inductive element is connected in parallel. The controller may be configured to identify multiple peaks in the measured current. Each peak may represent a resonant frequency in a distinct inductive element.
[0016] The controller may be configured to determine a phase difference between a voltage applied to at least one inductive element and a current in at least one inductive element. At least one resonant frequency may be identified based on the determined phase difference. The controller may be configured to control a power module to change the supply frequency of the alternating current and to determine the phase difference. Identifying at least one resonant frequency may include identifying one or more supply frequencies at which the phase difference results in at least substantially zero.
[0017] An induction heating system may include multiple induction elements. A controller may be configured to identify multiple resonant frequencies of alternating current supplied to the induction elements. The controller may identify distinct resonant frequencies for each induction element.
[0018] The controller is configured to determine the operating temperature of a component based on an identified resonant frequency. The controller may be configured to determine the operating temperature of a section or region of a component associated with a specific one of the inductive elements. In at least a given embodiment, the controller may determine the localized operating temperature of a part of the component. For example, the controller may determine the localized operating temperature of a section or region based on the identified resonant frequency of an inductive element associated with the section or region of the component.
[0019] According to another aspect of the present invention, an induction heating system for heating a component is provided, the induction heating system comprises the following:
[0020] Multiple guiding elements for positioning close to the outside of the component;
[0021] At least one power module for outputting alternating current to an induction element; and
[0022] A controller configured to identify multiple resonant frequencies of alternating current supplied to at least one induction element. The controller can identify distinct resonant frequencies for each induction element. The controller may be configured to control the operation of at least one power module, for example, to control the frequency of the alternating current output to the induction element.
[0023] The alternating current output from the induction element generates an alternating magnetic field to produce current within the component to perform heating. The controller can be configured to control the power module to control the supply frequency of the alternating current.
[0024] The controller can be configured to determine how many inductive elements are connected in parallel to the power module based on multiple identified resonant frequencies. Each identified resonant frequency may represent a distinct inductive element. The controller can determine that each identified resonant frequency indicates the presence of an inductive element. The controller can count the number of identified resonant frequencies and determine that the result of this count is the total number of inductive elements. The controller can identify one or more resonant frequencies, each corresponding to an inductive element of the induction heating system.
[0025] The controller may be configured to determine the operating temperature of a component based on an identified resonant frequency. The controller may determine the operating temperature of a section or region of the component associated with a specific one of the inductive elements. In at least a given embodiment, the controller may determine the localized operating temperature of a part of the component. For example, the controller may determine the localized operating temperature of that section or region based on the identified resonant frequency of the inductive element associated with the section or region of the component.
[0026] The controller may be configured to control the power module to change the supply frequency of the alternating current. The controller may measure the current across at least one inductive element as a function of the supply frequency. The controller may control the power module to implement substantially continuous or incremental (step) changes in the supply frequency.
[0027] The controller may be configured to monitor changes in the measured current that depend on changes in the supply frequency of the alternating current. The controller may be configured to identify multiple peaks in the measured current. A peak or each peak may include an increase or spike in the measured current. A peak or each peak may be associated with a distinct subset or region of the supply frequency. The controller may identify a resonant frequency corresponding to each peak of the measured current. Identification of multiple resonant frequencies may include identifying the supply frequency of the alternating current corresponding to the peak in the measured current. Each supply frequency causing a peak in the measured current may represent resonant inductive coupling. Resonant inductive coupling may be established between an inductive element and a component. Resonance results in a reduction in the phase shift between the current and the applied voltage, leading to a decrease in circuit impedance, which in turn leads to an increase in the current across at least one inductive element. Power transfer to the component increases at the resonant frequency.
[0028] The controller can be configured to identify the supply frequency of the power module corresponding to each peak detected in the measured current. Each peak may correspond to a distinct resonant frequency, for example, when more than one inductive element is connected in parallel. The controller can be configured to identify multiple peaks in the measured current. Each peak may represent a resonant frequency in a distinct inductive element.
[0029] The controller may be configured to control the power module to decrease the frequency offset between the supply frequency and the identified resonant frequency to increase or maintain the heating of the component; and / or to increase the frequency offset between the supply frequency and the identified resonant frequency to decrease the heating of the component. This control strategy may be performed for each identified resonant frequency. If the controller identifies multiple resonant frequencies, the frequency offset between the supply frequency and the identified resonant frequency may be controlled for each identified resonant frequency. This control strategy may enable thermal control of each of multiple induction elements.
[0030] The controller may be configured to control the power module to selectively control the supply frequency of the alternating current output to at least one inductive element in order to maintain the component at a target temperature.
[0031] Alternatively or additionally, the controller may be configured to control the power module to selectively control the voltage supplied to at least one induction element to maintain the component at a target temperature. The supply voltage may be selectively switched ON and OFF to control the temperature of the component.
[0032] The controller may be configured to determine the operating temperature of the component based on the identified resonant frequency. Alternatively, or additionally, the controller may have an input for receiving a temperature signal from a temperature sensor, such as a thermocouple.
[0033] An induction heating system may include multiple induction elements. The induction elements may be connected to a power module in parallel or in series.
[0034] Each inductive element may be provided with a capacitor(s) associated with it. The capacitor(s) associated with each inductive element may have different capacitances. The capacitor(s) associated with each inductive element may have a unique capacitance. For example, a first capacitor associated with a first inductive element may have a different capacitance from a second capacitor associated with a second inductive element. In at least certain embodiments, the different capacitances of the capacitors associated with the inductive elements may result in different resonant frequencies for each inductive element. The controller can thereby identify the presence or absence of each inductive element.
[0035] The capacitor(s) may be provided in the inductive element. Alternatively, or additionally, the capacitor(s) may be provided in the power module.
[0036] According to another aspect of the present invention, an induction heating system for heating a component is provided, the induction heating system comprises the following:
[0037] A power module for outputting alternating current to a first induction element and a second induction element - the first induction element and the second induction element are connected in parallel;
[0038] A first capacitor associated with a first induction element and a second capacitor associated with a second induction element—the first and second capacitors have different capacitances. In at least a given embodiment, the different capacitances of the first and second capacitors may appear at different resonant frequencies for the first and second induction elements. An induction heating system may include a controller configured to identify the presence or absence of each of the first and second induction elements based on the identification of the resonant frequency. It will be understood that an induction heating system may include one or more additional induction elements—each having a capacitor associated with itself. Each capacitor in the induction heating may have a different capacitance.
[0039] The first and second capacitors may be provided in the power module. Alternatively, the first and second capacitors may be provided in the first and second inductive elements, respectively.
[0040] The induction heating system may include a controller. The controller may be configured to identify first and second resonant frequencies of alternating current supplied to first and second induction elements. The controller may be configured to identify the presence and absence of first and second induction elements based on the identification of the first and second resonant frequencies.
[0041] An induction heating system may include a plurality of power modules. Each power module may be configured to supply alternating current to one or more of the plurality of induction elements.
[0042] Power modules can be connected to each other in a daisy-chain arrangement. Power modules can be connected to each other in series. Power modules can be connected to a common power source, for example, a main power source. The main power source can be a general-purpose voltage in the range of, for example, 100 V to 460 V.
[0043] The controller can be configured to control power modules independently of each other. Control signals can be transmitted from the controller between power modules, for example, along connections forming a daisy-chain array.
[0044] Each induction element may include an induction coil or be composed of an induction coil.
[0045] The component is electrically conductive. The component may be composed of, for example, a metal or a metal alloy. The component may include a conduit or may be composed of a conduit.
[0046] According to another aspect of the present invention, an induction heating controller for controlling a variable frequency alternating current (AC) power module configured to supply alternating current to at least one induction element is provided, wherein the controller comprises at least one processor and a memory device, and at least one processor is:
[0047] To change the supply frequency of the alternating current;
[0048] To monitor the current in at least one induction element as the supply frequency of the alternating current changes;
[0049] To identify at least one resonant frequency of alternating current supplied to at least one inductive element by a power module; and
[0050] It is configured to determine the operating temperature of the component based on at least one identified resonant frequency.
[0051] At least one processor may be configured to identify at least one resonant frequency by identifying at least one peak in the measured current that indicates at least one resonant inductive coupling.
[0052] At least one processor may be configured to determine the phase difference between the voltage applied to at least one inductive element and the current in at least one inductive element. At least one resonant frequency may be identified based on the determined phase difference. At least one processor may be configured to control a power module to change the supply frequency of the alternating current and to determine the phase difference. Identifying at least one resonant frequency may include identifying a supply frequency at which the phase difference results in at least substantially zero.
[0053] According to another aspect of the present invention, a power module for outputting alternating current to a first induction element and a second induction element is provided, wherein the power module is:
[0054] A first output for connection to a first inductive element; and
[0055] Includes a second output for connection to a second inductive element;
[0056] The first and second outputs are configured to connect the first and second induction elements in parallel with each other;
[0057] A first capacitor is associated with a first output and a second capacitor is associated with a second output, and the first and second capacitors have different capacitances. The different capacitances of the first and second capacitors may result in different resonant frequencies of the first and second inductive elements. When connected to the first inductive element, the first capacitor may be arranged in series with the first inductive element. When connected to the second inductive element, the second capacitor may be arranged in series with the second inductive element. A controller may be provided to detect the presence and absence of the first and second inductive elements, respectively, by relying on the identification of different resonant frequencies.
[0058] According to yet another aspect of the present invention, a component is provided that includes at least one integrated induction element for connection to an alternating current (AC) power module that generates an alternating magnetic field to generate an current within the component to perform heating. The induction element may include an induction coil or may be composed of an induction coil. An electrical insulator may be provided between the component and the induction coil. For example, an electrically insulating sheet or panel may be provided between the component and the induction coil. The sheet or panel may also optionally have thermal insulating properties to reduce heat loss from the component. The induction element may be formed as a separate component and then fastened to the component. The component may have a unitary configuration. At least one induction element may be permanently attached.
[0059] According to another aspect of the present invention, an induction heating device is provided comprising an induction element for connection to an alternating current (AC) power module that generates an alternating magnetic field to generate an electric current within an electrically conductive component to perform heating, wherein the induction element has a longitudinal alternating configuration. The induction element may include an induction coil or may be composed of an induction coil. The induction coil may include a longitudinal alternating configuration. The induction coil may be arranged in a single plane. In use, the substrate may be configured to be placed in close proximity to or in contact with the component.
[0060] An induction heating device may include means for electrically insulating an induction coil. An induction element may be placed on an electrically insulating member for positioning relative to a component. The electrically insulating member may be deformable to facilitate positioning of an induction element that is in close proximity to or in contact with a component.
[0061] According to another aspect of the present invention, an induction heating device is provided comprising an induction element for connection to an alternating current (AC) power module that generates an alternating magnetic field to generate an electric current inside an electrically conductive component to perform heating.
[0062] An induction heating device may be configured to be connected to other similar induction heating devices. An induction heating device may include a connector for connecting to similar induction heating devices. An induction heating device may be configured to be connected in parallel to other similar induction devices. An induction heating device may be configured to be connected together in a daisy-chain configuration.
[0063] An induction heating device may include a capacitor associated with an induction element. The capacitor may be arranged in series with the induction element. An induction heating device may be identifiable within an induction heating system by identifying a resonant frequency influenced by the capacitance of the capacitor. A set comprising multiple induction heating devices may be supplied, and each induction heating device may have a different capacitance. Different capacitances may manifest as different resonant frequencies of the induction element in each induction heating device. A controller may be provided to detect the presence and absence of each induction heating device by relying on the identification of different resonant frequencies.
[0064] According to an embodiment of the present invention, an induction heating system for heating a component is provided, and the induction heating system is:
[0065] Power module for outputting AC - The power module is capable of operating to output AC at a variable supply frequency - ;
[0066] A controller for controlling a power module to selectively control the supply frequency of alternating current; and
[0067] Includes at least one guiding element for positioning close to the outside of the component;
[0068] The power module is configured to supply alternating current to at least one induction element that generates an alternating magnetic field to generate current within the component to perform heating.
[0069] According to yet another aspect of the present invention, a method for heating a component by induction heating is provided, the method comprising the following:
[0070] Outputting alternating current to at least one induction element positioned close to the outside of the component;
[0071] Determining at least one resonant frequency of an alternating current output from at least one inductive element; and
[0072] Determining the operating temperature of a component based on at least one identified resonant frequency.
[0073] The method may include controlling the supply frequency of the alternating current output to at least one inductive element. At least one resonant frequency may be determined as the supply frequency changes.
[0074] The method may include measuring a current across at least one inductive element as a function of the supply frequency. The method may include monitoring a change in the measured current in dependence on a change in the supply frequency of the alternating current. Identifying at least one resonant frequency may include identifying at least one peak in the measured current and identifying a corresponding resonant frequency of the alternating current output by the power module.
[0075] The method may include determining a phase difference between a voltage applied to at least one inductive element and a current in the inductive element depending on a change in the supply frequency of the alternating current. Identifying the resonant frequency or each resonant frequency may include identifying when the phase difference is at least substantially zero (0).
[0076] Alternating current can be output to multiple inductive elements. The inductive elements can be connected in parallel. The method may include identifying multiple resonant frequencies of the alternating current supplied to the inductive elements. The method may include determining how many inductive elements are connected based on the multiple resonant frequencies.
[0077] The alternating current can be output to at least one induction element that generates an alternating magnetic field to generate an current inside the component to perform heating.
[0078] The method may include controlling the supply frequency of the alternating current. The controller may change the supply frequency of the alternating current supplied to at least one induction element. The change in supply frequency may be implemented substantially continuously or incrementally.
[0079] The method may include monitoring changes in the measured current based on changes in the supply frequency of the alternating current.
[0080] The method may include identifying at least one peak in the measured current. At least one peak may indicate a decrease in impedance that may indicate, for example, the establishment of resonant inductive coupling between the inductive element and the component. The resonant frequency of the alternating current output by the power module may be identified. If the supply frequency of the alternating current is at least substantially the same as the resonant frequency, power transfer to the component is increased.
[0081] The method may include identifying multiple peaks in the measured current. Each peak may represent resonant inductive coupling in each inductive element.
[0082] The method may include determining how many inductive elements are connected in parallel to the power module by relying on the identification of at least one peak in the measured current. The method may include counting the number of peaks in the measured current to determine how many resonant frequencies occur. The result of this count may represent the total number of inductive elements. The method may include identifying one or more peaks (representing each resonant frequency) corresponding to one or more inductive elements.
[0083] The method may include identifying the supply frequency of the power module corresponding to each peak detected in the measured current.
[0084] The method may include controlling the supply frequency to control the temperature of the component. A frequency offset between the instantaneous supply frequency and the identified resonant frequency. The method may include decreasing the frequency offset to increase or maintain the heating of the component. Alternatively, or additionally, the method may include increasing the frequency offset to decrease the heating of the component.
[0085] According to another aspect of the present invention, a method for heating a component by induction heating is provided, the method comprising the following:
[0086] Outputting alternating current to at least one induction element positioned close to the outside of the component;
[0087] Controlling the supply frequency of alternating current output to at least one inductive element;
[0088] Determining at least one resonant frequency of an alternating current output from at least one inductive element; and
[0089] Determining the operating temperature of a component based on at least one identified resonant frequency.
[0090] According to another aspect of the present invention, a method for heating a component by induction heating is provided, the method comprising the following:
[0091] Outputting alternating current to at least one induction element positioned close to the outside of the component;
[0092] Controlling the supply frequency of alternating current output to at least one induction element; and
[0093] Determining at least one resonant frequency of the alternating current output by at least one inductive element.
[0094] The method may include determining the temperature of a component based on an identified resonant frequency. Alternatively or additionally, the method may include using a temperature sensor to transmit the temperature of the component.
[0095] It should be understood that a controller or each controller may comprise a control unit or computational device having one or more electronic processors (e.g., a microprocessor, a microcontroller, an application-specific integrated circuit (ASIC), etc.), or may comprise a single control unit or computational device, or alternatively, different functions of the controller or each controller may be embodied or hosted in different control units or computational devices. As used herein, the terms “controller,” “control unit,” or “computational device” will be understood to include a single controller, control unit, or computational device, and a plurality of controllers, control units, or computational devices that operate collectively to provide the necessary control functionality. In practice, a set of instructions may be provided to enable the controller to implement the control technology described herein (including some or all of the functionality required for the method described herein). The set of instructions may be embedded in the one or more electronic processors of the controller; Alternatively, a set of instructions may be provided as software to be executed on a controller. The first controller or control unit may be implemented as software running on one or more processors. One or more other controllers or control units may be implemented as software running on one or more processors, optionally the same as the first controller or control unit. Other arrangements are also useful.
[0096] It is expressly intended that, within the scope of this application, the various aspects, embodiments, examples, and alternatives described in the foregoing paragraphs, claims, and / or the following description and drawings, and in particular individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiments may be combined in any manner and / or combination, provided that such features are not incompatible. The applicant reserves the right to modify any originally submitted claims or to submit any corresponding new claims, including the right to modify the originally submitted claims in such a manner so as to be dependent on any feature of any other claim and / or to incorporate any feature of any other claim, even if such feature was not originally claimed. Brief explanation of the drawing
[0097] Now, one or more embodiments of the present invention will be described merely as examples with reference to the accompanying drawings, in which: FIG. 1 illustrates a schematic representation of a thermal management system including an induction heating system according to an embodiment of the present invention; FIG. 2 illustrates a schematic representation of a first induction heating device for a thermal management system illustrated in FIG. 1; FIG. 3 illustrates a first circuit showing the connection of a first induction heating element to a first power module; FIG. 4 is a first graph showing the current measured across the first induction heating element shown in FIG. 3 with respect to the supply frequency; FIG. 5 is a schematic representation of a thermal management system including a single induction heating element connected to a power module; FIG. 6 is a flowchart illustrating the operation of the thermal management system illustrated in FIG. 5; FIG. 7 is a schematic representation of a thermal management system comprising a plurality of induction heating elements having power modules connected in a daisy-chain arrangement; FIG. 8 is a schematic representation of a thermal management system comprising a plurality of induction heating elements connected in parallel to a common power module; FIG. 9 illustrates a second circuit showing a parallel connection of the induction heating elements illustrated in FIG. 8; and FIG. 10 is a second graph showing the current measured at each end of the induction heating element shown in FIG. 9. Specific details for implementing the invention
[0098] Now, with reference to the attached drawings, an induction heating system (1) according to an embodiment of the present invention will be described. In this embodiment, the induction heating system (1) forms part of a thermal management system (TMS) (generally indicated by reference numeral 2). The induction heating system (1) operates to perform induction heating of an electrically conductive component (3). In this embodiment, the component is in the form of a conduit (3) comprising one or more subsections (3-n).
[0099] The induction heating system (1) operates to control the temperature of the exhaust system (4) for transporting process gas to the reduction device (5). The exhaust system (4) may be provided, for example, to transport deposited gas and associated powder discharged from a chemical vapor deposition (CVD) process. The induction heating system (1) is configured to control the temperature of the exhaust system (4) so as to ensure that the compound remains volatile and thereby prevent or suppress the accumulation of solids that could partially or completely block the exhaust system (2). It will be understood that the induction heating system (1) may be used in other industrial processes.
[0100] As illustrated in FIG. 1, the exhaust system (4) includes a conduit (3). The conduit (3) is in the form of a tube made of a metal such as stainless steel. The conduit (3) may include, for example, a DN40 pipe having an internal diameter of 40 mm. The conduit (3) may have a wall thickness of, for example, approximately 1 mm or 2 mm. It will be understood that the conduit (3) may have a larger or smaller wall thickness. The conduit (3) may, for example, be longer than 10 meters and may follow a very complex path. The conduit (3) forms a substantially continuous fluid path for transporting exhaust gas to the reduction device (4). The conduit (3) may consist of a pipe of a single length. However, the conduit (3) typically includes a plurality of subsections (3-1, 3-2) joined together in a fluid-tight manner. The conduit (3) may include one or more bends to provide the necessary connection to the reduction device (4). The conduit (3) is supported by a plurality of supports (6) along its length. An inlet coupling (9) is provided at the inlet (10) of the exhaust system (4); and an outlet coupling (11) is provided at the outlet (12) of the exhaust system (4). The outlet coupling (11) is provided to connect the exhaust system (4) to the reduction device (4). Each of the inlet and outlet couplings (9, 11) includes an O-ring to form a fluid seal with the associated component. A valve (13) is provided at the outlet (12) of the exhaust system (4). The valve (13) is operable to selectively open and close the outlet (12). The valve (13) may be heated to reduce the accumulation of solids. Lagging (14) is provided around the outside of the conduit (3) to thermally insulate the conduit (3).
[0101] An induction heating system (1) comprises a controller (20), at least one alternating current (AC) power module (21-n), and at least one induction heating device (22-n). The controller (20) comprises at least one electronic processor (23) and a system memory (24). A set of calculation instructions is stored in the system memory (24). When executed, the calculation instructions cause the processor (23) to perform the method(s) described herein. The power module (21-n) comprises an electrical input (25) connected to a main power supply (RMS) or another power source; and an electrical output (26) connected to at least one induction heating device (22-n). The power module (21-n) is configured to output high-frequency alternating current. The power module (21-n) may output alternating current having a frequency of, for example, 10 kHz or higher. The power module (21-n) may be a radio frequency (RF) power module for outputting alternating current having a supply frequency including an RF signal, for example, a supply frequency of 20 kHz or higher. In this embodiment, the power module (21-n) is configured to output alternating current having a frequency of 100 kHz or higher. In a variation, the power module (21-n) may be configured to generate alternating current having a frequency within the range of 100 kHz to 1000 kHz. The power module (21-n) in this embodiment is a variable frequency AC power module (21-n). A controller (20) is connected to the power module (21-n) (by either a wired connection or a wireless connection). The controller (20) operates to control the operation of the power module (21-n) to control the supply frequency of the alternating current output to at least one induction heating device (22-n) through the output unit (26). As illustrated in FIG. 1, the controller (20) transmits a control signal (CS1) to the power module (21-n) to control the supply frequency.The controller (20) may optionally be configured to receive one or more signals from the power module (21-n). In this embodiment, the controller (20) is configured to receive a current measurement signal from the power module (21-n). The power module (21-n) may be configured to operate at a relatively low voltage (e.g., less than 40 V) and a relatively high current (e.g., 10 amperes).
[0102] At least one induction heating device (22-n) is configured to be positioned with respect to (i.e., in contact with) the conduit (3) or in very close proximity to the conduit (3). Multiple induction heating devices (22-n) may be provided on the conduit (3). The induction heating devices (22-n) may be arranged on the conduit (3) in a non-overlapping arrangement. In this embodiment, at least one induction heating device (22-n) is configured to extend at least substantially around the perimeter of the conduit (3). Multiple induction heating devices (22-n) may be connected in series or in parallel to a power module (21-n). In the arrangement exemplified in FIG. 1, multiple induction heating devices (22-n) are provided on the conduit (3). The induction heating devices (22-n) provide multiple temperature control zones (Z(n)) for controlling the temperature of corresponding sections of the conduit (3). One or more induction heating devices (22-n) may be provided in each of the temperature control zones (Z(n)). Each of the induction heating devices (22-n) has the same configuration. For brevity, the description herein covers the configuration and operation of the first of the induction heating devices (22-1).
[0103] As illustrated in FIG. 2, the first induction heating device (22-1) comprises an induction element (27-1), a first protection member (28), and a second protection member (29). The induction element (27-1) comprises an induction coil (30); and first and second electrical connectors (31A, 31B) for connection to the output (26) of the power module (21-n). The induction coil (30) is configured to establish a concentrated magnetic field penetrating the conduit (3). The induction coil (30) is positioned between the first protection member (28) and the second protection member (29). In this embodiment, the induction coil (30) comprises an electrically conductive, slender member. The induction coil (30) has low resistance at the target operating frequency, or within the target operating frequency range. The induction coil (30) may be formed from one or more wires, for example, in the form of Litz wire; Alternatively, it may be machined from a continuous sheet of electrically conductive material. The induction coil (30) has a longitudinally alternating configuration, for example, including a sinusoidal curved configuration or a serpentine configuration, or composed of these. The induction coil (30) is formed in a single plane, and this arrangement is referred to herein as a "longitudinal coil." The induction coil (30) is supported between the first protective member (28) and the second protective member (29). The induction coil (30) may be joined to at least one of the first and second protective members (28, 29). Alternatively or additionally, the first and second protective members (28, 29) may be joined to each other to form a first induction heating device (22-1). The induction coil (30) may be placed in a recessed track or channel formed in at least one of the first and second protective members (28, 29).
[0104] The first protective member (28) is suitable for positioning on the outside of the conduit (3). The first and second protective members (28, 29) are electrically insulated. The first and second protective members (28, 29) may optionally be thermally insulated to reduce heat loss from the conduit (3). The first induction heating device (22-1) is deformable to facilitate positioning on the outside of the conduit (3), preferably around it. The first and second protective members (28, 29) include flexible panels. The first and second protective members (28, 29) may be formed from, for example, rubber or an elastomer compound. The first induction heating device (22-1) may include at least one fastener (not shown) for securing the first induction heating device (22-1) to the conduit (3). At least one fastener may be provided, for example, on the second protective member (29). At least one fastener may be detachable to facilitate positioning and / or removal of the first induction heating device (22-1). Suitable fasteners may include hook and loop fasteners disposed on the second protective member (29). Other types of fasteners may be utilized to secure the first induction heating device (22-1).
[0105] The induction heating system (1) in this embodiment includes at least one temperature sensor (32) for outputting a temperature signal (T(n)) to a controller (20). The temperature sensor (32) may include, for example, a thermistor or the like. In the arrangement shown in FIG. 1, a plurality of temperature sensors (32) are provided on the conduit (3). The temperature sensors (32) are associated with distinct temperature control zones (Z(n)) of the induction heating system (1). The temperature sensors (32) are thermally coupled to the conduit (3). The temperature sensors (32) may be bonded to the conduit (3), for example. In a variation, the temperature sensors (32) may be integrated into the first induction heating device (22-1), for example, on the outer surface of the first protective member (28) for positioning outside the conduit (3). Other techniques may be utilized to determine the temperature of the conduit (3). As described herein, the electrical behavior of the induction coil (30) can be monitored to determine the temperature of the conduit (3).
[0106] A schematic representation of a first circuit (EC1) comprising a power module (21-n) and an induction element (27-n) is shown in FIG. 3. As described above, the power module (21-n) is operable to output alternating current to at least one induction heating device (22-n). An oscillating electric field in the induction element (27-n) generates an oscillating magnetic field that penetrates the conduit (3) of the exhaust system (4). The conduit (3) is made of an electrically conductive material, and the changing magnetic field generates eddy currents within it. The eddy currents are effective in heating the conduit (3) at a rate determined by the resistance of the conduit (3). Although the first circuit (EC1) has an inherent ability to store electric charge (i.e., capacitance), a separate capacitor (33) is added to control the electrical behavior. The inductive element (27-n), capacitor (33), and resistor (34) are arranged in series in the first circuit (EC1). The resistor (34) may be a separate component provided in the first circuit (EC1). Alternatively, the resistor (34) may represent the resistance of an inductive load having eddy current generation losses that are a source of heating. Resonant inductive coupling is established when the supply frequency is at the resonant frequency (f0). The effective impedance of the first circuit (EC1) is reduced (typically to a minimum value), and current and power transfer are maximized. The resonant frequency (f0) can be determined by the following equation:
[0107]
[0108] Here: f0 is the resonance frequency and;
[0109] ω0 is the wavelength;
[0110] L is inductance; and
[0111] C is capacitance.
[0112] The inductance (L) of the first circuit (EC1) is a function of the material properties of the conduit (3) and also a function of the configuration of the coil formed by the inductive element (27-n). A first graph (50) showing the current (I) measured in the first circuit (EC1) over a range of wavelengths output by the power module (21-n) is shown in FIG. 4. For the purposes of this example, the resistance (R) is 1 ohm (Ω); the inductance (L) is 1 henry (H); the capacitance (C) is 1 farad (F); and the voltage is 1 volt (V). There are two control strategies available to control the power input to the conduit (3): (a) a control strategy for selectively controlling the frequency of the alternating current supplied to the inductive element (27-n); and (b) a control strategy for modulating the supply voltage while maintaining a fixed frequency of the alternating current (e.g., switching the supply voltage ON / OFF). In this embodiment, the power module (21-n) is a variable frequency AC power module (21-n), and a preferred control strategy is to change the supply frequency of the alternating current. A technique for controlling the frequency of the alternating current to control power delivery to the conduit (3) is illustrated by an arrow in the first graph (50). The controller (20) is configured to control the power module (21-n) to adjust the frequency of the alternating current output to the induction element (27-n). The controller (20) may be configured to implement an incremental change (i.e., a step change) or a substantially continuous change in the supply frequency. By measuring the current (I) in the first circuit (EC1), the controller (20) can identify the resonant frequency (f0). The resonant frequency (f0) is affected by changes in the temperature of the base material, i.e., the conduit (3). By monitoring the resonant frequency (f0), the controller (20) can estimate the temperature of the conduit (3). Therefore, the temperature of the conduit (3) can be determined without the need for a temperature sensor (32).
[0113] A flowchart (100) illustrating the operation of the TMS (2) is shown in FIG. 6. Alternating current is output from the power module (21-n) to at least one inductive element (27-n) (block (110)). The supply frequency of the alternating current output to at least one inductive element is changed, for example, by scanning the supply frequency within a range (block (120)). The current (I) across at least one inductive element (27-n) is measured as a function of the supply frequency (block (130)). At least one peak is identified in the measured current, and the associated supply frequency is identified as the resonant frequency (f0) (block (140)). The temperature of the conduit (3) is determined (block (150)). The temperature of the conduit (3) can be determined based on the identified resonant frequency (f0) or based on a temperature signal received from the temperature sensor (32). The determined temperature of the conduit (3) is compared to a target temperature (block (160)). The controller (20) controls the supply frequency of the alternating current based on the determined temperature of the conduit (3). If the temperature of the conduit (3) is lower than the target temperature, the controller (20) controls the supply frequency to reduce the frequency offset between the current supply frequency and the identified resonant frequency (f0) (block (170)). If the temperature of the conduit (3) is higher than the target temperature, the controller (20) controls the supply frequency to increase the frequency offset between the current supply frequency and the identified resonant frequency (f0) (block (180)). The process operates continuously while the industrial process is in progress.
[0114] Now, the operation of the TMS (2) will be described in more detail. The controller (20) sets a target temperature for each of the temperature control zones (Z(n)). The target temperature may be set according to operation or process characteristics, for example, depending on the composition of the exhaust gas being transported within the conduit (3). Now, the operation of an embodiment of the TMS (2) including a single induction heating device (22-1) will be described with reference to FIG. 5. The first induction heating device (22-1) is positioned on the outside of the conduit (3) and secured in place using fasteners. The induction element (27-1) of the first induction heating device (22-1) extends at least substantially around the circumference of the conduit (3) to promote uniform heating. The first induction heating device (22-1) is connected to the output (26) of the first power module (21-n) (21-1). The controller (20) outputs a control signal (CS1) for controlling the supply frequency of the alternating current connected to the first power module (21-n) (21-1) and output to the first induction heating device (22-1). The changing electric field in the induction element (27-1) generates an oscillating magnetic field that induces eddy currents causing direct heating of the conduit (3). The temperature sensor (32) measures the temperature of the conduit (3) and outputs a temperature signal (T(1)) to the first power module (21-n) (21-1) and / or the controller (20). The controller (20) is configured to control the supply frequency of the alternating current based on the measured temperature. If the temperature signal (T(n)) indicates a measured temperature below the target temperature, the controller (20) is configured to change the supply frequency to a frequency closer to the resonant frequency (f0) (by either increasing or decreasing the supply frequency) in order to increase power delivery. Accordingly, to increase the heating of the component, the frequency offset between the current supply frequency and the identified resonant frequency (f0) is reduced.If the temperature signal (T(n)) indicates a measured temperature exceeding the target temperature, the controller (20) is configured to change the supply frequency (by either increasing or decreasing the supply frequency) so that the supply frequency moves further away from the resonant frequency (f0) to reduce power delivery. By doing so, the frequency offset between the current supply frequency and the identified resonant frequency (f0) is increased to reduce heating of the component.
[0115] As described above, the resonant frequency (f0) varies with temperature. The relationship between the resonant frequency (f0) and the measured temperature of the conduit (3) can be predefined, for example, in a lookup table stored in the system memory (24). Accordingly, the controller (20) can determine the temperature of the conduit (3) based on the determined resonant frequency (f0). Alternatively or additionally, the controller (20) may be configured to control the power module (21-n) to change the supply frequency to determine the resonant frequency (f0). The supply frequency may be changed within a range, for example, to perform a scan or sweep. The controller (20) may change the supply frequency, for example, between a lower frequency limit and an upper frequency limit. In this embodiment, the controller (20) is configured to change the supply frequency substantially continuously between the lower frequency limit and the upper frequency limit. In a variation, the controller (20) may be configured to implement incremental changes, for example, including a plurality of step changes in the supply frequency. The controller (20) measures a current (i1) across the first induction heating device (22-1) as the supply frequency changes. The controller (20) is configured to identify a peak of the measured current (i1) as a function of the supply frequency. The peak may be identified by determining when the rate of change of the measured current as the supply frequency changes is at least substantially equal to zero (0). The controller (20) identifies a resonant frequency (f0) as the frequency corresponding to the peak current. To determine the resonant frequency (f0), the controller (20) may selectively increase or decrease the supply frequency depending on whether the rate of change of the measured current is positive or negative. Alternatively, the controller (20) may measure the current for a predefined range of the supply frequency. This process can be performed periodically, for example, as a calibration operation.
[0116] The development of the TMS (2) is illustrated in FIG. 7. This implementation of the TMS (2) includes a plurality of induction heating devices (22-n) each associated with a separate section of the conduit (3). The TMS (2) of this arrangement includes a plurality of temperature control zones (Z(n)) each comprising at least one induction heating device (22-n). In the illustrated arrangement, the TMS (2) includes four (4) induction heating devices (22-1, 22-2, 22-3, 22-4) and four (4) associated power modules (21-1, 21-2, 21-3, 21-4). Each of the induction heating devices (22-1, 22-2, 22-3, 22-4) is connected to each of the power modules (21-1, 21-2, 21-3, 21-4). The power modules (21-1, 21-2, 21-3, 21-4) are daisy-chained together and powered via a common line voltage connection, thereby minimizing the number of connections to the central power distribution board. Each power module (21-1, 21-2, 21-3, 21-4) receives a temperature signal (T(n)) from an associated temperature sensor (32). The controller (20) is configured to control the supply frequency of the alternating current output from each of the power modules (21-1, 21-2, 21-3, 21-4) based on the temperature signal (T(n)). The supply frequency of the alternating current output to each induction heating device (22-1, 22-2, 22-3, 22-4) can be controlled independently. Thus, the temperature of a separate temperature control zone (Z(n)) can be controlled independently.
[0117] The power modules (21-n) may be configured to communicate directly with the controller (20) (represented by the dashed line shown in FIG. 5). In a variation, the power modules (21-n) are configured to communicate with each other via a line voltage connection connected in a daisy-chain manner. Each power module (21-n) is configured to transmit and receive signals via the line voltage connection. The first power module (21-n) (21-1) associated with the first induction heating device (22-1) may function as a master unit that communicates directly with the controller (20). The second, third, and fourth power modules (21-2, 21-3, 21-4) associated with the subsequent induction heating devices (22-2, 22-3, 22-4) function as slave units. This connection provides the advantage of providing a single point of communication connection to the controller (20). In this arrangement, the line voltage connection operates to transmit a control signal (CS1) to each power module (21-n) to control the supply frequency output to each induction heating device (22-2, 22-3, 22-4). A temperature signal (T(n)) and other operation signals may optionally be transmitted via the line voltage connection. The current across each induction heating device (22-2, 22-3, 22-4) may optionally be measured and transmitted via the line voltage connection. It will be understood that each power module (21-n) may operate independently of other power modules (21-n). The power requirement in the main electrical connection is equal to the sum of the individual power requirements of each of the AC power module (21-n) units (21).
[0118] Another embodiment of the TMS (2) is illustrated in FIG. 8. The same reference numerals are used for the same components. The TMS (2) includes a plurality of temperature control zones (Z(n)), each comprising at least one section of the conduit (3). The TMS (2) includes a plurality of induction heating devices (22-n), each connected in parallel to a common power module (21-n). In the illustrated embodiment, there are three (3) induction heating devices (22-1, 22-2, 22-3) connected in parallel to the first power module (21-n) (21-1). Each of the first, second, and third induction heating devices (22-1, 22-2, 22-3) is associated with a distinct section of the conduit (3) (corresponding to a distinct temperature control zone (Z(n))). The temperature of the distinct sections of the conduit (3) can be controlled independently.
[0119] A second circuit (EC2) representing this embodiment of the TMS (2) is illustrated in FIG. 9. The second circuit (EC2) includes a plurality of branches connected in parallel to the AC supply module (21-1). Each branch corresponds to one of the temperature control zones (Z(n)). In the illustrated arrangement, the second circuit (EC2) includes three (3) branches, but it will be understood that the second circuit (EC2) may include two (2) branches or more than three (3) branches. The second circuit (EC2) includes first, second, and third capacitors (33-1, 33-2, 33-3) having first, second, and third capacitances (C1, C2, C3), respectively. Each of the first, second, and third capacitors (33-1, 33-2, 33-3) may have different capacitances (C1, C2, C3) to change the resonant frequency of each branch of the second circuit (EC2). The current flow in each branch of the second circuit (EC2) depends on the supply frequency of the current output by the first power module (21-n) (21-1). It will be understood that more than one induction heating device (22-n) may be provided in each temperature control zone (Z(n)), and, for example, two or more induction heating devices (22-n) may be connected in series within each branch of the second circuit (EC2).
[0120] The controller (20) is configured to control the power module (21-n) to change the supply frequency in order to determine the resonant frequency (f0) of each branch of the second circuit (EC2). The supply frequency may be changed within a range, for example, between a lower frequency limit and an upper frequency limit. In this embodiment, the controller (20) controls the power module (21-n) so that the supply frequency changes substantially continuously. The current (I) in each branch of the second circuit (EC2) is measured as the supply frequency changes over the range. In this embodiment, the controller (20) measures the first current (i1), the second current (i2), and the third current (i3) across the first, second, and third induction heating devices (22-1, 22-2, 22-3), respectively. The controller (20) operates to identify the peaks in each of the first current (i1), the second current (i2), and the third current (i3) as a function of the supply frequency. The peaks at each of the first current (i1), the second current (i2), and the third current (i3) correspond to the resonant frequency (f0) at each of the first, second, and third induction heating devices (22-1, 22-2, 22-3). The controller (20) is configured to determine the temperature of each section of the conduit (3) based on the resonant frequency (f0) for each branch of the second circuit (EC2). The controller (20) may also control the temperature of each section of the conduit (3) by controlling the AC supply module (21-1) to adjust the supply frequency. Alternatively or additionally, the temperature of each section of the conduit (3) may be changed by optionally adjusting the inductance and / or capacitance of each branch of the second circuit (EC2).
[0121] The controller (20) is described as measuring the current (I) across each of the induction heating devices (22-1, 22-2, 22-3). The total current (I) is equal to the sum of the first current (i1), the second current (i2), and the third current (i3) (i.e., I = i1 + i2 + i3). Each of the first current (i1), the second current (i2), and the third current (i3) comprises a vector described in the complex domain having phase and module. The total current (I) can be measured, and the presence or absence of a resonant frequency (f0) can be determined by detecting one or more peaks in the total current (I) as a function of the supply frequency. The controller (20) can monitor the total current (I) and count the total number of peaks present in the total current (I) across a range of the supply frequency. The identification of each peak in the total current (I) indicates the resonant frequency (f0) of a distinct temperature control zone connected in parallel to the power module (21-n). By determining how many peaks exist across the supply frequency range, the controller (20) can determine how many (n) induction heating devices (22-n) are connected. The controller (20) can determine that there are no connected induction heating devices (22-n) (i.e., n = 0); or that there is one or more connected induction heating devices (22-n) (n >= 1). By doing so, the controller (20) can discover how many temperature control zones (Z(n)) are connected to the power module (21-n). The ability to determine how many induction heating devices (22-n) are connected can enable the implementation of an automated or semi-automated control system.
[0122] A second graph (60) representing the current (I) measured in the second circuit (EC2) within the range of wavelengths output by the first power module (21-n) (21-1) is shown in FIG. 10. The power module (21-n) is a variable frequency AC power module (21-n), and the control strategy includes controlling the supply frequency of the alternating current output to the inductive elements (27-1, 27-2, 27-3). The controller (20) may be configured to implement an incremental change (i.e., a stepwise change) or a substantially continuous change in the supply frequency. By measuring the first current (i1), the second current (i2), and the third current (i3), the controller (20) can identify the resonant frequency (f0) of each inductive element (27-1, 27-2, 27-3). The resonant frequency (f0) is affected by a change in the temperature of the substrate, i.e., the conduit (3). By monitoring the resonant frequency (f0), the controller (20) can estimate the temperature of each section of the conduit (3). The controller (20) is configured to control the first power module (21-n) (21-1) based on the determined temperature of the corresponding section of the conduit (3).
[0123] A variable capacitor and / or a variable inductor may be provided in each branch of the second circuit (EC2). The controller (20) may be configured to control the capacitance and / or inductance in each branch to adjust the resonant frequency (f0) of each inductive element (27-1, 27-2, 27-3).
[0124] At least one induction heating device (22-n) is described herein as a separate device located on the conduit (3). In a variation, the induction heating device (22-n) may be integrated into the component (3). In particular, an induction element (27-n) may be integrated into the conduit (3). The induction element (27-n) may include a spiral one extending around the circumference of the conduit (3). Alternatively, the induction element (27-n) may include a longitudinal coil of the type described herein that extends at least partially around the circumference of the conduit (3). The induction element (27-n) will be electrically and optionally also thermally insulated from the conduit (3). For example, an electrical insulating sheath may be provided around the outside of the conduit (3). Each section (3-1, 3-2) of the conduit (3) may include an electrical connector. An electrical connector may be used to connect the inductive elements (27-n) to each other (e.g., in parallel or in series) and / or to power module(s) (21-n). The conduit (3) may include coupling means to form a fluid seal with an adjacent conduit (3). A thermal insulation layer and / or an electrical insulation layer may be provided around the outer side of the inductive elements (27-n).
[0125] It will be recognized that various changes and modifications can be made to the present invention without departing from the scope of this application.
[0126] The controller (20) is described herein as determining the resonant frequency (f0) by measuring the current (i1) across the first induction heating device (22-1) as the supply frequency changes. The resonant frequency (f0) is identified as the supply frequency corresponding to the peak of the measured current (i1). It will be understood that other techniques may be used to determine the resonant frequency (f0). For example, the resonant frequency (f0) may be determined by monitoring the phase and current of the voltage applied to the induction element (27-n). At resonance, the phase is ineffective because the circuit is purely resistive (corresponding to the maximum power being transmitted). If the frequency is greater than the resonant frequency (f0) (f > f0), the circuit behaves rather like an inductance with current 'behind' the voltage. If the frequency is less than the resonant frequency (f0) (f < f0), the circuit behaves rather like a capacitor with current 'in front' of the voltage. Therefore, phase detection may be used to determine the resonant frequency (f0). The controller (20) may be configured to control the frequency of the alternating current supplied to the induction element (27-n) based on the determined phase. Explanation of the symbols
[0127]
Claims
Claim 1 An induction heating system (1) for heating a component (3), comprising a plurality of induction elements (27-n) for being positioned close to the outside of the component (3), at least one power module (21-n) for outputting alternating current to the plurality of induction elements (27-n), and a controller (20) configured to identify a plurality of resonant frequencies (f0) of the alternating current supplied to the plurality of induction elements (27-n), wherein the controller (20) is configured to determine the operating temperature of the component (3) based on the identified resonant frequencies (f0), and the controller (20) is configured to determine how many induction elements (27-n) are connected in parallel to the power module (21-n) based on the number of identified resonant frequencies (f0). Claim 2 In claim 1, the controller (20) is configured to control the power module (21-n) to change the supply frequency of the alternating current and to measure the current across the plurality of induction elements (27-n) as a function of the supply frequency, wherein identifying the plurality of resonant frequencies (f0) includes identifying the supply frequency of the alternating current corresponding to the plurality of peaks of the measured current, induction heating system (1) for heating a component (3). Claim 3 In claim 1, the controller is configured to control the power module (21-n) to change the supply frequency of the alternating current and to determine the phase difference between the voltage applied to the plurality of induction elements (27-n) and the current in the induction elements (27-n), wherein identifying the plurality of resonant frequencies (f0) includes identifying the supply frequency at which the phase difference becomes zero (0). Induction heating system (1) for heating a component (3). Claim 4 An induction heating system (1) for heating a component (3), comprising a plurality of induction elements (27-n) for being positioned close to the outside of the component (3), at least one power module (21-n) for outputting alternating current to the induction elements (27-n), and a controller (20) configured to identify a plurality of resonant frequencies (f0) of the alternating current supplied to the plurality of induction elements (27-n), wherein the controller (20) is configured to determine how many induction elements (27-n) are connected in parallel to the power module (21-n) depending on the number of identified resonant frequencies (f0). Claim 5 In paragraph 4, the induction heating system (1) for heating the component (3) is configured such that the controller (20) determines the operating temperature of the component (3) based on the identified resonant frequency (f0). Claim 6 delete Claim 7 An induction heating system (1) for heating a component (3), wherein, in any one of claims 1 to 5, the controller (20) is configured to control the power module (21-n) such that at least one of reducing the frequency offset between the supply frequency and the identified resonant frequency (f0) to increase or maintain the heating of the component (3), and increasing the frequency offset between the supply frequency and the identified resonant frequency (f0) to decrease the heating of the component (3). Claim 8 In any one of claims 1 to 5, the induction heating system (1) for heating a component (3) is connected in parallel to the power module (21-n). Claim 9 In claim 8, each induction element (27-n) is provided with a capacitor (C1, C2, C3) associated with itself, and each capacitor (C1, C2, C3) has a different capacitance, induction heating system (1) for heating a component (3). Claim 10 delete Claim 11 delete Claim 12 delete Claim 13 delete Claim 14 delete Claim 15 delete Claim 16 delete Claim 17 delete Claim 18 A method for heating a component (3) by induction heating, comprising the steps of: outputting alternating current to a plurality of induction elements (27-n) disposed in close proximity to the outside of the component (3); identifying a plurality of resonant frequencies (f0) of the alternating current output to the plurality of induction elements; and determining the operating temperature of the component (3) based on the identified resonant frequencies (f0). The method further comprises the step of determining a phase difference between a voltage applied to the plurality of induction elements (27-n) and a current in the induction elements (27-n) based on a change in the supply frequency of the alternating current, wherein the step of identifying the plurality of resonant frequencies (f0) includes the step of identifying when the phase difference is zero (0). Claim 19 A method for heating a component (3) by induction heating, wherein, in claim 18, the method comprises the step of measuring a current across the plurality of induction elements (27-n) as a function of a supply frequency and monitoring a change in the measured current depending on a change in the supply frequency of the alternating current, wherein the step of identifying the plurality of resonant frequencies (f0) includes the step of identifying at least one peak in the measured current and the step of identifying a corresponding resonant frequency (f0) of the alternating current output by the power module (21-n). Claim 20 delete Claim 21 A method for heating a component (3) by induction heating, comprising the step of determining how many induction elements (27-n) are connected depending on the plurality of resonant frequencies (f0) in either of claims 18 and 19. Claim 22 A method for heating a component (3) by induction heating, comprising at least one of the steps of: reducing the frequency offset between the supply frequency and the identified resonant frequency (f0) to increase or maintain the heating of the component (3) in any one of claims 18 and 19; and increasing the frequency offset between the supply frequency and the identified resonant frequency (f0) to decrease the heating of the component (3).