Preventive maintenance system

Abstract

A preventive maintenance system according to an embodiment of the present invention comprises: an induction heating device having an inductor including a coil that heats a material to be heated by electromagnetic induction of a high-frequency current from an inverter; a voltage detector that detects and outputs a voltage of the coil; a current detector that detects and outputs a current of the coil; and a control device that calculates an impedance of a circuit including the coil on the basis of the detected voltage and current. The control device calculates the impedance on the basis of the voltage and current detected before the material to be heated reaches the coil or after the material to be heated is discharged from the coil, and stores the calculated impedance in association with each time when the voltage and the current used to calculate the impedance are detected.

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a preventive maintenance system for induction heating devices. [Background technology]

[0002] In the hot rolling line, the rolled material is heated in a heating furnace to a rolling temperature, then roughly rolled in a roughing mill to form a rough-rolled bar. The formed rough-rolled bar is then finished-rolled in a finishing mill to the desired plate thickness and width to produce the product.

[0003] Generally, in a hot rolling line, the load on the rolling mill increases as the temperature of the steel decreases. Therefore, induction heating devices are sometimes installed to raise the temperature of the rolled material, equalize the heat, and reduce the load. The rolled material that is heated by the induction heating device is called the heated material.

[0004] Induction heating devices are known, such as edge heaters for raising the temperature of the edges on both sides of the material to be heated, bar heaters for raising the temperature of the entire material in the width direction, and soaking heaters for raising the temperature of the central part of the material in the width direction.

[0005] Steel manufacturing equipment is operated over long periods, and is required to produce high-quality products during these long-term operations. Induction heating equipment installed in the line also needs to operate continuously for extended periods. If induction heating equipment suddenly stops operating due to aging or deterioration, investigating the cause and taking countermeasures would necessitate a prolonged shutdown, raising concerns about the impact on line operations.

[0006] Therefore, from the perspective of preventing the shutdown of induction heating devices, proposals have been made regarding preventive maintenance of induction heating devices, and for example, the technology disclosed in Patent Document 1 is known. In the technology disclosed in Patent Document 1, the deterioration status of any part inside the induction heating device is detected using a temperature sensor with an optical fiber.

[0007] In the technology disclosed in Patent Document 1, the deterioration status of the inductor can be monitored over time by installing a temperature sensor between the heating coil and the heat-resistant plate that constitute the inductor. On the other hand, maintenance of the induction heating device must be performed when the line is stopped, and the temperature sensor is exposed to high temperatures until the maintenance is performed. As a result, the temperature sensor itself may deteriorate, or in severe cases, it may burn out. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2012-163459 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] Maintenance of induction heating equipment often requires numerous inspection items, and depending on the nature of the inspection, it can take a considerable amount of time. Therefore, it is necessary to plan and implement preventive maintenance in advance. There is a growing need to establish methods for accurately understanding the deterioration status of induction heating equipment and conducting efficient maintenance inspections by focusing on key maintenance points through preventive maintenance.

[0010] The embodiments of the present invention have been made to solve the above-mentioned problems, and aim to provide a preventive maintenance system that can accurately grasp the deterioration status of an induction heating device. [Means for solving the problem]

[0011] A preventive maintenance system according to an embodiment of the present invention includes an induction heating device having an inductor including a coil that heats a heated material by electromagnetic induction by flowing a high-frequency current supplied from an inverter, a voltage detector that detects and outputs a voltage applied to the coil, a current detector that detects and outputs a current flowing through the coil, and a control device that calculates an impedance of a circuit including the coil based on the voltage detected by the voltage detector and the current flowing detected by the current detector. The coil is formed by winding a hollow tubular conductor and is cooled by cooling water circulating within the conductor. In the inductor, the cooling water circulates within the conductor, which is divided into multiple regions. The inductor includes a first temperature sensor for detecting the temperature of the cooling water before cooling, a plurality of second temperature sensors provided in the plurality of regions for detecting the temperature of the cooling water in each of the plurality of regions, and a plurality of flow sensors provided in the plurality of regions for detecting the flow rate of the cooling water in each of the plurality of regions. The control device calculates the impedance based on the voltage and the current detected before the heated material reaches the coil or after the heated material is discharged from the coil, and associates and stores the calculated impedance for each date and time when the voltage and the current for calculating the impedance are detected. This enables the output of time-series data of the impedance, and calculates multiple heat extraction amounts in the multiple regions based on the data of the cooling water temperature before cooling detected by the first temperature sensor, the data of the cooling water temperatures in the multiple regions detected by the multiple second temperature sensors, and the data of the cooling water flow rates in the multiple regions detected by the multiple flow rate sensors. By storing this data in association with the date and time on which the temperature data and the flow rate data were acquired, it enables the output of time-series data of the multiple heat extraction amounts for each of the multiple regions. 。

Advantages of the Invention

[0012] According to an embodiment of the present invention, a preventive maintenance system capable of accurately grasping the deterioration status of an induction heating device is provided.

Brief Description of the Drawings

[0013] [Figure 1] It is a schematic block diagram illustrating a preventive maintenance system according to an embodiment. [Figure 2] It is a schematic equivalent circuit diagram of a heating coil of an inductor. [Figure 3] It is a schematic diagram illustrating an inductor. [Figure 4] It is a schematic diagram illustrating an inductor. [Figure 5] It is a schematic diagram illustrating a cooling system of an inductor that is part of a preventive maintenance system according to an embodiment.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. Please note that the drawings are schematic or conceptual, and the relationships between the thickness and width of each part, as well as the ratios of the sizes of the parts, are not necessarily identical to those of reality. Furthermore, even when representing the same part, the dimensions and ratios may differ between drawings. In this specification and in each figure, elements similar to those described above are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.

[0015] Figure 1 is a schematic block diagram illustrating a preventive maintenance system according to an embodiment. As shown in Figure 1, the preventive maintenance system 100 according to this embodiment includes a bar heater 1, a measuring transformer 5, a measuring current transformer 6, a capacitor 9, and a control device 10.

[0016] The bar heater 1 has an inductor 2. The inductor 2 has a heating coil 13 made of a wound conductor, as will be described in detail with reference to Figures 3 and 4, to which an inverter 18 is electrically connected. The heating coil 13 generates a magnetic field by a high-frequency current output from the inverter 18, and the magnetic field generated by the heating coil 13, through electromagnetic coupling with the material to be heated 15, generates a high-frequency induced current in the material to be heated 15. The material to be heated 15 is heated by this induced current.

[0017] Capacitor 9 is connected in parallel to the heating coil 13 of inductor 2. Capacitor 9 forms a parallel resonant circuit with the heating coil 13 and also adjusts the power factor to the heating coil 13.

[0018] The measuring transformer 5 is provided to detect the voltage across the heating coil 13 of the inductor 2. The measuring transformer 5 detects the voltage across the heating coil 13 at a predetermined interval and outputs the detected voltage data to the control device 10.

[0019] The current transformer 6 is provided to detect the current flowing through the parallel circuit between the heating coil 13 and the capacitor 9. The current transformer 6 detects the current flowing through the parallel circuit between the heating coil 13 and the capacitor 9 at a predetermined period and outputs the detected current data to the control device 10. The current detection period coincides with the voltage detection period.

[0020] The control device 10 is connected to the outputs of the measuring transformer 5 and the measuring current transformer 6, respectively. The control device 10 sequentially calculates the impedance of the parallel circuit based on the voltage data across the heating coil 13 output by the measuring transformer 5 and the current data flowing through the parallel circuit between the heating coil 13 and the capacitor 9. The control device 10 stores the parallel circuit impedance data calculated when there is no material to be heated in the inductor 2.

[0021] Figure 2 is a schematic equivalent circuit diagram of the heating coil of an inductor. As shown in Figure 2, the heating coil 13 of inductor 2 can be represented as a series circuit of inductances L1-L3 and resistors R1-R3. This series circuit of inductances L1-L3 and resistors R1-R3 is connected in parallel with capacitor 9. An inverter 18 is connected across the parallel circuit between the heating coil 13 and capacitor 9.

[0022] The inductance L1 and resistor R1 have inductance and DC resistance values, respectively, for functioning as a heating coil 13. The inductance value of inductance L1 is approximately equal to the self-inductance value of the heating coil 13, and the DC resistance value of resistor R1 is approximately equal to the DC resistance value of the conductor of the heating coil 13.

[0023] The inductance L2 and resistance R2 represent the impedance generated by the electromagnetic coupling between the heating coil 13 and the material to be heated 15 when the material to be heated 15 is present inside the inductor 2. The inductance value of inductance L2 and the DC resistance value of resistance R2 are determined according to the material to be heated. If the material to be heated 15 is not present inside the inductor 2, the inductance value of inductance L2 and the DC resistance value of resistance R2 are approximated to 0 and can be ignored.

[0024] The inductance L3 and resistance R3 represent the impedance generated by electromagnetic induction between the heating coil 13 and scale or other metal-containing compounds (hereinafter referred to as "scale, etc.") that have peeled off from the heated material 15, etc. Since the scale, etc. accumulates inside the inductor 2 over time, the inductance value of inductance L3 and the DC resistance value of resistance R3 are determined by the area and thickness of the accumulated scale, etc., regardless of whether the heated material 15 is present inside the inductor 2. The larger the area and the thicker the accumulation of scale, etc., the greater the inductance value of inductance L3.

[0025] Figure 3 is a schematic diagram illustrating an inductor. As shown in Figure 3, in the inductor 2 of the bar heater 1, the material to be heated 15 is conveyed through the opening of the inductor 2. A heat-resistant plate 16 is provided inside the opening of the inductor 2. The heat-resistant plate 16 is provided to protect the inductor 2 from radiant heat from the material to be heated 15. A shield cover 17 is provided around the inductor 2. The shield cover 17 is provided to reduce the impact of electromagnetic waves radiated from the inductor 2 on the surrounding environment.

[0026] In a hot rolling line, scale removal equipment such as a descaler is installed to remove scale formed on the surface of the rolled material before and after rolling. Even when a descaler is installed, some scale may remain attached to the material to be heated 15 and be fed into the bar heater 1. Due to the long-term operation of the induction heating device, the scale remaining on the material to be heated 15 fed into the bar heater 1 may peel off inside the inductor 2 due to vibrations during transport, etc., and adhere to and accumulate inside the inductor 2.

[0027] The scale and other deposits adhering to and accumulating inside the inductor 2 are, from the perspective of the induction heating device, equivalently forming an inductive load consisting of inductance L3 and resistance R3, as shown in Figure 2. Therefore, if the amount of scale and other deposits increases, the induction heating device will supply power to the scale and other deposits accumulated together with the material being heated 15. To compensate for insufficient heating of the material being heated 15, it will be necessary to supply more power than usual, which may accelerate the deterioration of electrical components such as the inductor 2 and capacitor 9, as well as insulating materials. Furthermore, if the supplied power is maintained, there is a concern that the material being heated 15 will not be heated sufficiently, increasing the load on the subsequent finishing rolling mill.

[0028] Therefore, in the preventive maintenance system 100 according to the embodiment, the impedance of the circuit including the heating coil 13 is calculated as data representing information on the adhesion and accumulation status of scale, etc. More specifically, the preventive maintenance system 100 calculates the impedance of the parallel circuit between the heating coil 13 and the capacitor 9 when there is no material to be heated 15 in the inductor 2. This makes it possible to store the impedance data of the parallel circuit, which eliminates the influence of the inductance L2 and resistance R2 determined according to the material to be heated, as time-series data. The stored time-series data of the impedance of the parallel circuit can be output as information for preventive maintenance.

[0029] When the bar heater output command information 12 is active, power is supplied to the parallel circuit consisting of the heating coil 13 and the capacitor 9, and when the bar heater output command information 12 is inactive, the power supply to the parallel circuit is stopped. For example, in a specific example of introducing an induction heating device to a hot rolling line, the bar heater output command information 12 becomes active a predetermined time before the time when the material to be heated 15 enters the inductor 2. Also, the bar heater output command information 12 becomes inactive a predetermined time after the time when the material to be heated 15 passes through the inductor 2 and is discharged from the inductor 2.

[0030] The control device 10 can calculate the impedance of the parallel circuit using the voltage and current data of the parallel circuit acquired during the period when the bar heater output command information 12 is active, a predetermined time before the time when the material to be heated 15 enters the inductor 2. Alternatively, the control device 10 may calculate the impedance of the parallel circuit using the voltage and current data of the parallel circuit acquired during the period when the bar heater output command information 12 is active, after the material to be heated 15 has been discharged from the inductor 2.

[0031] When there is no material to be heated 15 inside the inductor 2 and the bar heater output command information 12 is active, the impedance Z of the parallel circuit between the heating coil 13 and the capacitor 9 can be calculated according to the following equation (1).

[0032] Z = ZL / (1 + jω·ZL·C) (1) Here, ZL is the sum of the impedance of the heating coil and the impedance due to the scale, and is expressed by the following equation (2). ZL = R1 + R3 + jω·(L1 + L3) (2)

[0033] The control device 10 calculates the impedance Z in equation (1) and stores it, for example, by separating it into its real and imaginary parts. The control device 10 may also calculate and store the magnitude |Z| and phase angle of the impedance Z.

[0034] The control device 10 stores the real and imaginary values ​​of the impedance Z as time-series data, associating them with the date and time on which the voltage data detected by the measuring transformer 5 and the current data detected by the measuring current transformer 6 were acquired. Since the voltage and current data are measured synchronously at a predetermined period, the time-series data related to impedance calculated by the control device 10 is synchronized with the time on which the voltage and current data were acquired.

[0035] When the bar heater output command information 12 is active and the material to be heated 15 is not present in the inductor 2, the time-series data of the impedance Z of the circuit including the heating coil 13 can be output to a monitor connected to the control device 10 by, for example, an operator operating the preventive maintenance system 100. For example, the control device 10 has a threshold value for impedance Z. The threshold value can be set based on experimental or performance data, etc. For example, the operator can check the time-series data and threshold value displayed on the monitor 11 and plan to perform equipment maintenance work on the inductor 2 on the next scheduled equipment inspection date if the impedance Z data reaches the threshold value.

[0036] The control device 10 may have multiple threshold levels. If the calculated and stored impedance Z data reaches the higher of the multiple threshold levels, the control device 10 may warn to schedule an emergency equipment maintenance activity for the next line downtime. By setting it in this way, it is possible to warn when a more rapid response is needed, and to prevent line downtime due to unforeseen circumstances.

[0037] In the specific example described above, the impedance Z of the parallel circuit between the heating coil 13 and the capacitor 9 is calculated, stored, and output to understand the accumulation of scale and other materials on the inductor 2. As shown in Figure 1, if a coil current measuring current transformer 7 can be provided to detect the current flowing through the heating coil 13, the impedance can be calculated using the current of the heating coil 13 and the voltage across the heating coil 13. This time-series data of the real and imaginary parts of the impedance may be used for maintenance activities. In the description of the specific example above, it was assumed that voltage data and current data of the parallel circuit consisting of the heating coil 13 and the capacitor 9 were acquired sequentially, but this is not the only option. For example, voltage data and current data of the parallel circuit may be acquired when the bar heater output command information 12 is active and there is no material to be heated 15 inside the inductor 2, and data acquisition may be stopped during other periods.

[0038] In the preventive maintenance system 100 according to this embodiment, in addition to understanding the accumulation status of scale and other deposits due to impedance changes in the heating coil 13, the amount of heat removed by the cooling system of the heating coil 13 can be calculated and the calculated amount of heat removed can be used in preventive maintenance activities. The amount of heat removed is the amount of heat when the cooling system cools the heating coil 13 that is to be cooled.

[0039] As shown in Figure 1, in the preventive maintenance system 100 according to this embodiment, the bar heater 1 has temperature sensors 3 and 8 and a flow sensor 4. The outputs of temperature sensors 3 and 8 are connected to the control device 10. The output of flow sensor 4 is also connected to the control device 10.

[0040] Temperature sensors 3 and 8 are provided to measure the temperature of the cooling water for the inductor 2. Temperature sensor 8 detects the temperature of the cooling water before cooling the inductor 2 and outputs the detected data to the control device 10. Temperature sensor 3 detects the temperature of the cooling water after cooling the inductor 2 and outputs the detected data to the control device 10.

[0041] The flow sensor 4 is provided to detect the flow rate of the cooling water for the inductor 2. For example, the flow sensor 4 detects the flow rate of the cooling water after the inductor 2 has been cooled and outputs the detected data to the control device 10.

[0042] The control device 10 stores data on the temperature of the cooling water before and after cooling, as well as data on the flow rate of the cooling water, as time-series data, associated with the date and time when this data was acquired.

[0043] The configuration and operation of the preventive maintenance system 100 according to this embodiment will be described in more detail. In the preventive maintenance system 100 according to this embodiment, the cooling water piping for the inductor 2 is also used for the heating coil 13. Figure 4 is a schematic diagram illustrating an inductor. As shown in Figure 4, the inductor 2 has a heating coil 13 and a mold 14. The mold 14 covers the periphery of the wound heating coil 13. The mold 14 is provided to insulate the heating coil 13. The mold 14 is also provided to improve the heat dissipation of the heating coil 13 and to protect the heating coil 13 from the ingress of scale, water, etc.

[0044] Most of the current flowing through the heating coil 13 flows near the surface of the conductors constituting the heating coil 13 due to the skin effect of high-frequency currents. Even if bulk conductors are used in the heating coil 13, almost no current flows near the center of the conductors. Therefore, in the bar heater 1, as shown in Figure 4, a hollow tubular conductor is wound and applied to the heating coil 13.

[0045] Since the heating coil 13 is composed of a hollow tubular conductor, by connecting the cooling system to the heating coil 13, the heating coil 13 itself can be used as piping for the cooling system. Furthermore, using a hollow tubular conductor for the heating coil 13 has the advantage of making the heating coil 13 lighter.

[0046] Figure 5 is a schematic diagram illustrating an inductor cooling system, which is part of a preventive maintenance system according to the embodiment. In Figure 5, to avoid illustration complexity, the heating coil 13, which is formed from a hollow tubular body, is shown with a thick line. In reality, the thick line represents a tube, and cooling water can flow through the inside of the tube. Pure water is used as the cooling water for cooling the inductor 2 to ensure insulation even if a leak occurs.

[0047] As shown in Figure 5, electromotive force terminals 20a and 20b are connected to both ends of the heating coil 13 of the inductor 2, and the inductor 2 is electrically connected to the inverter 18 via the electromotive force terminals 20a and 20b. As shown in Figure 3, the material to be heated 15 is transported through the opening, so the heating coil 13 is wound around the material to be heated 15 as it passes through the opening.

[0048] In the specific example shown in Figure 5, an inlet and outlet for cooling water flowing through the inside of the heating coil 13 are provided for each turn of the heating coil 13. A hose nipple 21 is provided at each of the inlet and outlet, and the inlet and outlet are fluidically connected to the cooling pipe. Hose nipples are also provided at both ends of the heating coil 13 and are fluidically connected to the cooling pipe.

[0049] The cooling system for inductor 2 includes main pipes 22 and 23 as cooling pipes. In the specific example shown in Figure 5, main pipe 22 is a pipe through which cooling water pumped from a cooling tank (not shown) flows, for example, and main pipe 23 is a pipe that returns cooling water that has flowed through the heating coil 13 and cooled the heating coil 13 back to the cooling tank.

[0050] The main pipe 22 is provided with n control pipes 22-1 to 22-n. The main pipe 23 is provided with n control pipes 23-1 to 23-n. In the specific example of FIG. 5, the heating coil 13 is wound n times. More specifically, the control pipes 22-1 to 22-n are fluidly connected to the heating coil 13 in the order in which they are wound around the heating coil 13. The control pipes 23-1 to 23-n are fluidly connected to the heating coil 13 in the order in which they are wound around the heating coil 13.

[0051] More specifically, the first wound coil is fluidly connected to the control pipe 22-1 so as to introduce cooling water from one side of the wound coil, and is fluidly connected to the control pipe 23-1 so as to discharge cooling water from the other side. The cooling water flowing through this portion enters the heating coil 13 at a flow rate CW1 and is discharged at a flow rate CW1'. The flow rate CW1 and the flow rate CW1' are equal. The cooling water with the flow rate CW1 enters the heating coil 13 from the control pipe 22-1 and is discharged from the control pipe 23-1. Similarly, the cooling water flowing through the nth wound coil enters the heating coil 13 at a flow rate CW n and is discharged from the heating coil 13 at a flow rate CW n . The flow rate CW n and the flow rate CW n ' are equal. The cooling water with the flow rate CW n enters the heating coil 13 from the control pipe 22-n and is discharged from the control pipe 23-n.

[0052] The flow rate sensors 4-1 to 4-n respectively detect the flow rates CW1' to CW n '(= the flow rates CW1 to CW n ) and output the detected data to the control device 10.

[0053] The heat extraction amount P loss i of the i-th wound coil is calculated by the following formula (3).

[0054] P loss i = (T out i - T in )·CW i (3) Here, i is an integer from 1 to n. Also, T outi is the temperature of the cooling water flowing through the control pipe 23-i, as detected by the temperature sensor 3-i, T in This represents the temperature of the cooling water before cooling, as detected by the temperature sensor 8.

[0055] Temperature T of the cooling water before cooling in This is detected by the temperature sensor 8. The temperature of the cooling water after cooling T out 1~T out n is detected by temperature sensors 3-1 to 3-n, respectively. Cooling water flow rates CW1 to CW n These are detected by flow sensors 4-1 to 4-n, respectively.

[0056] The control device 10 controls the temperature T in , T out 1~T out n and flow rate CW1~CW n Applying each of the data to equation (3), we obtain the amount of heat removed P for each region. loss 1~P loss n is calculated. The control device 10 controls the temperature T in , T out 1~T out n and flow rate CW1~CW n The amount of heat removed from each region P at the time of detection loss 1~P loss Store n data points in an associated manner.

[0057] Furthermore, it is preferable that the detection of physical quantities by temperature sensors 3-1 to 3-n, 8 and flow rate sensors 4-1 to 4-n be performed when the material to be heated 15 is not present inside the inductor 2. When the bar heater output command information 12 is inactive, the material to be heated 15 is not present inside the inductor 2, and temperature data and flow rate data can be acquired without being affected by the radiant heat from the material to be heated 15. In addition, the acquisition of temperature data and flow rate data may be synchronized with the acquisition of voltage data and current data of the parallel circuit between the heating coil 13 and the capacitor 9. By doing so, the configuration of programs and other components related to the acquisition and calculation of each data can be simplified.

[0058] As in this specific example, the control device 10 calculates the amount of heat removed for each region corresponding to the position of the winding coil, stores the time-series data of the calculated amount of heat removed, and outputs it, thereby outputting which region of the winding coil of the heating coil 13 is experiencing an increase in heat removal. The operator of the preventive maintenance system 100 can determine the amount of heat removed P for each winding coil of the n-th wound heating coil 13. loss By observing the time-series data of i (an integer from 1 to n), and recognizing which region of the heating coil 13 is experiencing increased heat generation, it is possible to estimate which region is where scale or other deposits are present.

[0059] The control device 10 may output the heat removal data for the 1st to nth regions to the monitor 11 via software that graphically displays the data. In such a case, the heating coil 13 can be graphically displayed, and the estimated locations of high-temperature areas and areas where scale or other deposits have formed can be displayed on the graphical data of the heating coil.

[0060] The effects of the preventive maintenance system 100 according to this embodiment will be explained. The preventive maintenance system 100 according to this embodiment can detect the current flowing through the inductor 2 constituting the bar heater 1 and the voltage applied across its terminals, and can calculate, store, and output impedance data related to the inductor 2 in a time series. Since the impedance related to the inductor 2 fluctuates in a time series due to the adhesion and accumulation of scale, etc., the state of adhesion and accumulation of scale, etc. can be indirectly recognized by observing the time series impedance data.

[0061] The impedance associated with inductor 2 differs depending on whether or not the heated material 15 is present inside inductor 2. Therefore, in the preventive maintenance system 100 according to this embodiment, the control device 10 acquires voltage and current data for calculating the impedance of inductor 2 when the heated material 15 is not present inside inductor 2. The control device 10 can determine the presence or absence of the heated material 15 inside inductor 2 by monitoring the tracking signal of the heated material 15 or by monitoring the output of a sensor installed near the bar heater 1. Furthermore, since the power supply to inductor 2 is controlled by the bar heater output command information 12, the impedance of inductor 2 can be calculated using voltage and current data acquired during the period when the bar heater output command information 12 is active and the heated material 15 is not present inside inductor 2. In this way, impedance data that fluctuates over time due to scale, etc., can be accurately calculated regardless of the heated material 15.

[0062] The detection means for acquiring voltage and current data to calculate the impedance associated with inductor 2 can utilize existing devices such as measuring transformer 5 and measuring current transformer 6, and can be easily introduced into existing bar heater 1.

[0063] Furthermore, in the preventive maintenance system 100 according to this embodiment, the bar heater 1 can acquire data on the temperature and flow rate of the cooling water in the cooling system for cooling the inductor 2, and calculate the amount of heat removed by the cooling water.

[0064] The heating coil 13, which constitutes the inductor 2, is constructed by winding a hollow tubular conductor. Cooling water can be circulated through the conductor of the heating coil 13, allowing for a highly efficient cooling effect.

[0065] The heating coil 13 is divided into regions, and the temperature and flow rate of the cooling water before and after cooling are detected for each region. Based on the detected temperature difference and flow rate, the amount of heat removed from each region of the heating coil 13 by the cooling water can be calculated. The amount of heat removed can be stored and output as time-series data by associating it with the date and time on which the temperature and flow rate data were acquired. By outputting time-series data of the amount of heat removed for each region of the heating coil 13, the operator of the preventive maintenance system 100 can understand the trend of changes in the amount of heat removed for each region of the heating coil 13.

[0066] The change in the amount of heat removed from each region of the heating coil 13 over time suggests that areas where the temperature rise of the heating coil 13 is localized to be large will have more scale buildup than other areas, which can be used as reference when formulating maintenance plans.

[0067] In the operation of the induction heating device, the host computer may transmit the power value required for heating as a command value to the control device 10 based on the attribute information of the material to be heated 15. The attribute information of the material to be heated 15 includes, for example, plate thickness, plate width, and transport speed. In this case, the difference between the temperature rise value based on the power command value and the calculated heat dissipation amount is considered to be the radiant heat of the material to be heated. The control device 10 calculates the radiant heat, stores it as time-series data, and outputs it, which can be used to determine the deterioration of the components of the inductor 2 due to radiant heat and as a reference for formulating a maintenance plan. Deterioration of components due to radiant heat includes, for example, deformation of the shield cover 17. Also, if a change is observed in the time-series data of radiant heat, it is possible that a gap has formed in the heat-resistant plate 16, and it is effective to include inspection of the heat-resistant plate 16 in the maintenance plan.

[0068] In the specific example described above, a bar heater was used as the induction heating device. However, the above points can be applied not only to bar heaters but also to other induction heating devices used in steel manufacturing lines, such as edge heaters and soaking heaters.

[0069] In this way, a preventive maintenance system is realized that can accurately grasp the deterioration status of induction heating equipment.

[0070] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. Furthermore, the embodiments described above can be implemented in combination with each other. [Explanation of Symbols]

[0071] 1…Bar heater, 2…Inductor, 3, 3-1~3-n, 8…Temperature sensor, 4, 4-1~4-n…Flow sensor, 5…Measurement transformer, 6…Measurement current transformer, 7…Current transformer for coil current measurement, 9…Capacitor, 10…Control device, 11…Monitor, 12…Bar heater output command information, 13…Heating coil, 14…Mold, 15…Material to be heated, 16…Heat-resistant plate, 17…Shield cover, 18…Inverter, 20a, 20b…Electricity terminal, 21…Hose nipple, 22, 23…Main piping, 22-1~22-n, 23-1~23-n…Control pipe, 100…Preventive maintenance system

Claims

1. An induction heating device having an inductor including a coil that heats the material to be heated by electromagnetic induction by passing a high-frequency current supplied from an inverter, A voltage detector that detects and outputs the voltage applied to the coil, A current detector that detects and outputs the current flowing through the coil, A control device that calculates the impedance of a circuit including the coil based on the voltage detected by the voltage detector and the current detected by the current detector, Equipped with, The coil is formed by winding a hollow tubular conductor and is cooled by cooling water circulating within the conductor. In the inductor, the cooling water circulates through the conductor which is divided into multiple regions. The aforementioned inductor is A first temperature sensor detects the temperature of the cooling water before cooling, A plurality of second temperature sensors are provided in the plurality of regions and each detects the temperature of the cooling water in the plurality of regions, A plurality of flow sensors provided in the plurality of regions for detecting the flow rate of the cooling water in the plurality of regions, It has, The control device is Based on the voltage and current detected before the heated material reaches the coil or after the heated material is discharged from the coil, the impedance is calculated, and the calculated impedance is associated and stored for each date and time the voltage and current for which the impedance was calculated were detected, thereby enabling the output of time-series data of the impedance. A preventive maintenance system that calculates multiple heat removal amounts in multiple regions based on data of the temperature of the cooling water before cooling detected by the first temperature sensor, data of the temperatures of multiple cooling water in multiple regions detected by the multiple second temperature sensors, and data of the flow rates of multiple cooling water in multiple regions detected by the multiple flow rate sensors, and stores the data in association with the date and time on which the temperature data and the flow rate data were acquired, thereby enabling the output of time-series data of the multiple heat removal amounts for each of the multiple regions.

2. The preventive maintenance system according to claim 1, wherein the induction heating device is of the bar heater type, edge heater type, or soaking heater type.

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