Power supply apparatus for thermal processing

Abstract

To provide a power supply device for heat processing capable of appropriately stopping an output before a component is damaged by heat when a cooling fan is abnormal without using many temperature sensors.SOLUTION: The welded power supply device A1 includes the power conversion unit 1 that converts input power into power for thermal processing, the control unit 2 that controls the power conversion unit 1, the housing 9 that houses the power conversion unit 1 and the control unit 2, at least one of the cooling fans 6 that cools the inside of the housing 9, and the detection units (the temperature sensor 3, the output current sensor 71, and the output voltage sensor 72) that detect the magnitudes of the temperature increase factors that increase the temperatures of the components of the power conversion unit 1. When detecting the abnormality of the cooling fan 6, the control part 2 sets a grace time corresponding to a value detected by the detection part, and stops the operation of the power conversion part 1 when the grace time elapses.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply device for thermal processing. [Background technology]

[0002] Conventionally, power supplies for thermal processing have been known that generate an arc between the tip of a torch electrode and a workpiece to perform thermal processing such as welding or cutting of the workpiece. Examples of power supplies for thermal processing include welding power supplies. Welding power supplies include heat-generating components such as switching elements and reactors, as well as a cooling fan for cooling these components. To prevent damage to the components due to heat, such as when the cooling fan malfunctions or when the cooling fan's airflow is insufficient, a temperature sensor is provided to detect the temperature of the heat-generating components. When the temperature detected by the temperature sensor exceeds a set temperature, the welding power supply determines that an abnormality has occurred and stops output to prevent further temperature rise. In this case, a temperature sensor is required for each heat-generating component, resulting in a large number of temperature sensors being required. Furthermore, when the temperature detected by the temperature sensor exceeds the set temperature, the welding power supply stops output, resulting in an abrupt halt to the welding operation.

[0003] Patent Document 1 discloses an information processing device that stops the supply of power from the power supply device after a predetermined time has elapsed if an abnormality in the cooling fan is detected. The information processing device can perform a shutdown operation within the predetermined time before the power supply is stopped. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-47757 Summary of the Invention [Problem to be solved by the invention]

[0005] The information processing device described in Patent Document 1 has a preset time period, and if a cooling fan malfunctions, the power supply is stopped when the preset time period has elapsed. In the case of a welding power supply, the welding current and welding voltage used for welding are set according to the material and thickness of the workpiece, the material and diameter of the welding wire, the joint shape, the welding position, the welding speed, the required penetration depth, and other factors. Different welding currents and welding voltages result in different temperature rises in heat-generating components. Therefore, even if the invention of Patent Document 1 is adopted in a welding power supply, there is a possibility that the temperature may rise too much within the preset time period, damaging the components.

[0006] The present invention was conceived in light of the above circumstances, and its object is to provide a power supply device for thermal processing that can appropriately stop output when an abnormality occurs in the cooling fan, before components are damaged by heat, without using multiple temperature sensors. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides the following technical means.

[0008] The power supply device for thermal processing according to the present invention comprises a power conversion unit that converts input power into power for thermal processing, a control unit that controls the power conversion unit, a housing that houses the power conversion unit and the control unit, at least one cooling fan that cools the inside of the housing, and a detection unit that detects the magnitude of a heating element that is an element that raises the temperature of components in the power conversion unit, and when the control unit detects an abnormality in the cooling fan, it sets a grace period corresponding to the value detected by the detection unit and stops operation of the power conversion unit when the grace period has elapsed.

[0009] In a preferred embodiment of the present invention, the detection unit includes an output current sensor that detects the output current of the power conversion unit, an output voltage sensor that detects the output voltage of the power conversion unit, and a temperature sensor that detects the internal temperature, which is the ambient temperature inside the housing, and the control unit sets the grace period based on the output current value detected by the output current sensor, the output voltage value detected by the output voltage sensor, and the temperature detection value detected by the temperature sensor.

[0010] In a preferred embodiment of the present invention, the detection unit further includes an input voltage sensor that detects the input voltage of the power conversion unit, and the control unit further sets the grace period based on the input voltage value detected by the input voltage sensor.

[0011] In a preferred embodiment of the present invention, there are a plurality of cooling fans, and the control unit further sets the grace period based on which cooling fan has experienced an abnormality.

[0012] In a preferred embodiment of the present invention, the power supply device further includes a notification unit that notifies the user that operation of the power conversion unit is to be stopped when the control unit detects an abnormality in the cooling fan. [Effects of the Invention]

[0013] According to the present invention, when a cooling fan abnormality is detected, the control unit stops operation of the power conversion unit after a grace period has elapsed. The grace period is set to a period corresponding to a value detected by a detection unit that detects the magnitude of a temperature rise factor. The grace period is set to an appropriate period depending on the detected value of a temperature rise factor (e.g., internal temperature, output current, output voltage, etc.). This reduces the possibility of the temperature rising too much during the grace period and damaging components. Furthermore, there is no need to provide a temperature sensor for each heat-generating component. As a result, the thermal processing power supply device according to the present invention can appropriately stop output in the event of a cooling fan abnormality before components are damaged by heat, without using multiple temperature sensors.

[0014] Other features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] 1A and 1B are diagrams for explaining a welding power supply according to a first embodiment, in which FIG. 1A is a block diagram showing the overall configuration of a welding system including the welding power supply, and FIG. 1B is a simplified diagram showing an example of the interior of a housing of the welding power supply. [Figure 2] FIG. 10 is a diagram illustrating an example of a grace period table. [Figure 3] 10 is an example of a flowchart illustrating an abnormality determination process. [Figure 4] FIG. 10 is a diagram showing an example of a modified example of the first table of the grace time table. [Figure 5] FIG. 6 is a block diagram showing the internal configuration of a welding power supply according to a second embodiment. [Figure 6] 10A and 10B are diagrams for explaining a welding power supply according to a third embodiment, in which FIG. 10A is a block diagram showing the internal configuration of the welding power supply, and FIG. 10B is a simplified diagram showing an example of the inside of the housing of the welding power supply. [Figure 7] 10 is an example of a flowchart illustrating an abnormality determination process according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, taking as an example a case where a power supply device for thermal processing according to the present invention is a welding power supply device.

[0017] [First embodiment] Figure 1 is a diagram illustrating a welding power supply A1 according to a first embodiment. Figure 1(a) is a block diagram showing the overall configuration of a welding system including welding power supply A1. Figure 1(b) is a simplified diagram showing an example of the interior of housing 9 of welding power supply A1.

[0018] The welding system shown in FIG. 1 includes a welding power supply A1, power cables C1 and C2, a wire feeder D, and a welding torch T.

[0019] One output terminal of the welding power supply A1 is conductively connected to the welding torch T via a power cable C1. The wire feeder D feeds the welding wire to the welding torch T, causing the tip of the welding wire to protrude from the tip of the welding torch T. The power cable C1 and the welding wire are electrically connected via a contact tip located at the tip of the welding torch T. The other output terminal of the welding power supply A1 is conductively connected to the workpiece W via a power cable C2. The welding power supply A1 generates an arc between the tip of the welding wire protruding from the tip of the welding torch T and the workpiece W, and supplies power to the arc. The welding system welds the workpiece W using the heat of the arc. Note that the configuration of the welding system is not limited. For example, the welding system may not include the wire feeder D and may use a non-consumable electrode instead of the welding wire.

[0020] Welding power supply A1 supplies DC power for arc welding to welding torch T. Welding power supply A1 includes a power conversion unit 1, a control unit 2, a temperature sensor 3, a memory unit 4, an alarm unit 5, multiple cooling fans 6, an output current sensor 71, an output voltage sensor 72, and a housing 9.

[0021] The power conversion unit 1 converts AC power input from, for example, a commercial power source into DC power suitable for welding and outputs the DC power. For example, the power conversion unit 1 includes a primary rectifier circuit, an inverter circuit, a transformer, and a secondary rectifier circuit, all of which are not shown. The primary rectifier circuit converts AC power into DC power and outputs the DC power. The inverter circuit converts the DC power output from the primary rectifier circuit into high-frequency AC power. The inverter circuit includes multiple switching elements 11. The high-frequency AC power is input to the secondary rectifier circuit via a transformer. The secondary rectifier circuit converts the high-frequency AC power into DC power and outputs the DC power. The secondary rectifier circuit includes a rectifier circuit and a reactor 13. Note that the configuration of the power conversion unit 1 is not limited to that described above.

[0022] Output current sensor 71 detects the output current of welding power supply A1 (power conversion unit 1). In this embodiment, output current sensor 71 is disposed on a connection line between one output terminal of power conversion unit 1 and an output terminal to which power cable C2 is connected. The location of output current sensor 71 is not limited. Output current sensor 71 outputs an output current detection signal corresponding to the output current to control unit 2.

[0023] Output voltage sensor 72 detects the output voltage of welding power supply A1 (power conversion unit 1). In this embodiment, output voltage sensor 72 detects the voltage between two output terminals of power conversion unit 1. Output voltage sensor 72 outputs an output voltage detection signal corresponding to the output voltage to control unit 2.

[0024] The housing 9 houses the power conversion unit 1, the control unit 2, and the like. In this embodiment, as shown in FIG. 1(b), the interior of the housing 9 includes a first chamber 91 that can take in outside air and a second chamber 92 that is dustproof to prevent the intrusion of dust and dirt from the outside. Components of the power conversion unit 1, such as the reactor 13 and the transformer, are disposed in the first chamber 91. Components such as a control board 20 that constitutes the control unit 2 and a wiring board on which each circuit of the power conversion unit 1 is mounted are disposed in the second chamber 92. Components such as the switching element 11 are located in the second chamber 92, while a heat sink 12 attached to the switching element 11 and the like is located in the first chamber 91. Note that the structure of the housing 9 and the arrangement of each component are not limited to those described above.

[0025] The multiple cooling fans 6 cool the various components inside the housing 9. In this embodiment, the welding power supply A1 is equipped with three cooling fans 6 (61, 62, 63). The number of cooling fans 6 is not limited and may be one, two, or four or more. Cooling fan 61 is located in the first chamber 91 and draws in outside air to primarily blow it toward the heat sink 12, which dissipates heat from the switching element 11 and other components. Cooling fan 62 is located in the first chamber 91 and draws in outside air to primarily blow it toward the reactor 13 and other components. Cooling fan 63 is located in the second chamber 92 and circulates air within the second chamber 92. As described above, each cooling fan 6 has a different location and a different target to be cooled. Therefore, the temperature of each component rises differently depending on which cooling fan 6 malfunctions. For example, if cooling fan 61 malfunctions, the temperature of the switching element 11 rises sharply, but this does not significantly affect the temperature rise of the reactor 13. The locations of the cooling fans 6 and the main objects to be cooled are not limited to those described above.

[0026] The temperature sensor 3 detects the internal temperature of the device, which is the ambient temperature inside the housing 9. The temperature sensor 3 is, for example, a thermistor, but is not limited to this. The temperature sensor 3 is placed in a position where it is less susceptible to the influence of heat-generating components. In this embodiment, the temperature sensor 3 is mounted on the control board 20 placed in the second chamber 92. The placement position of the temperature sensor 3 is not limited to this. The temperature sensor 3 outputs a temperature detection signal to the control unit 2 according to the detected internal temperature.

[0027] The memory unit 4 stores various information. The memory unit 4 stores, rewrites, and reads information in response to commands from the control unit 2. In this embodiment, the memory unit 4 stores a grace period table. The grace period table is a table for setting a grace period, which is the amount of time allowed before stopping the operation of the power conversion unit 1 when an abnormality occurs in the cooling fan 6. Even if an abnormality occurs in the cooling fan 6, the temperature of each component does not immediately rise and damage the component. Since it takes a certain amount of time for the component temperature to rise to a level that damages the component after the abnormality occurs, the operation of the power conversion unit 1 can be stopped before that time (grace period) has elapsed. The grace period differs depending on which cooling fan 6 has the abnormality, as well as the internal temperature, output current, and output voltage at that time. The grace period table stores the grace period in association with these pieces of information.

[0028] Fig. 2 is a diagram showing an example of a grace period table. In the example shown in Fig. 2, the grace period table is made up of a first table shown in Fig. 2(a) and a second table shown in Fig. 2(b).

[0029] The first table stores the correspondence between the state (normal or abnormal) of each cooling fan 6 and the second table to be referenced. In this embodiment, welding power supply A1 is equipped with three cooling fans 61, 62, and 63, and therefore, as shown in FIG. 2(a), the second table to be referenced is stored in association with the state of the first fan (cooling fan 61), the state of the second fan (cooling fan 62), and the state of the third fan (cooling fan 63). For example, if only the first fan is abnormal and the second and third fans are normal, the corresponding second table, "Table 1," is referenced.

[0030] The second table stores the correspondence between the internal temperature, output current, output voltage, and grace period. A second table is stored for each of Tables 1, 2, 3, etc., referenced based on the first table. The second table shown in FIG. 2(b) is "Table 1." As shown in FIG. 2(b), grace periods are stored in association with the internal temperature, output current, and output voltage. In the example shown in FIG. 2(b), the internal temperature is set to -20°C, 0°C, 20°C, and 40°C, the output current is set to 0A, 200A, and 300A, and the output voltage is set in 10V increments between 80V and 0V. For example, if the internal temperature is -20°C, the output current is 100A, and the output voltage is 80V, 60 seconds is referenced as the corresponding grace period. The internal temperature, output current, and output voltage are referenced using the closest values ​​set in the table. Note that, in the second table, each value may be set in smaller increments. Furthermore, the range of each value may be set to a wider range.

[0031] 2 is merely an example, and is not limited to this. For example, the grace period table may be a single table that stores the correspondence between the state of each cooling fan 6, the internal temperature, the output current, the output voltage, and the grace period.

[0032] The higher the internal temperature, the higher the temperature of each component within the housing 9. Furthermore, the higher the output current and output voltage of the welding power supply A1 (power conversion unit 1), the more heat is generated by each switching element 11, reactor 13, and transformer of the inverter circuit. In other words, the internal temperature, output current, and output voltage can be considered temperature-raising factors that increase the temperature of the components in the power conversion unit 1. Therefore, in this embodiment, the grace period is set based on the internal temperature, output current, and output voltage. Furthermore, the way in which the temperature of each component increases varies depending on which cooling fan 6 experiences an abnormality. Therefore, in this embodiment, the grace period is set based on the state of each cooling fan 6. The grace period table is set based on the detected time, for example, by changing the state of each cooling fan 6, the internal temperature, output current, and output voltage under each condition through experiments or simulations, and detecting the time it takes for the temperature of any component to exceed its heat-resistant temperature. The method for setting the grace period table is not limited.

[0033] The notification unit 5 notifies information in response to a command from the control unit 2. The notification unit 5 includes a light-emitting unit such as an LED, and notifies information by the light color or light emission mode (on, off, blinking, etc.) of the light-emitting unit. The notification unit 5 may include a display device such as a display, and notify information by an image displayed on the display device. The notification unit 5 may also include a speaker, and notify information by voice or buzzer sound.

[0034] Control unit 2 controls welding power supply A1 and is realized by, for example, a microcomputer. Control unit 2 controls the inverter circuit of power conversion unit 1 so that the output current of welding power supply A1 becomes the set current. Control unit 2 also controls the reading of information from memory unit 4, the operation of each cooling fan 6, and the reporting of information from notification unit 5. Control unit 2 has, as its functional configuration, a set value setting unit 21, a current control unit 22, a fan control unit 23, an abnormality detection unit 24, a grace time setting unit 25, a stop control unit 26, and a notification control unit 27.

[0035] Current control unit 22 is a functional component for controlling the output current of welding power supply A1. Current control unit 22 performs feedback control of the output current of welding power supply A1 based on a current detection signal input from output current sensor 71. Specifically, current control unit 22 generates a drive signal based on the difference between a current value corresponding to the current detection signal and a current command value input from set value setting unit 21, and outputs the drive signal to power conversion unit 1. Power conversion unit 1 controls the output current to the current command value by turning on and off each switching element of the inverter circuit based on the input drive signal.

[0036] The set value setting unit 21 is a functional component for setting set values. The operator sets the set value of each parameter of the welding conditions by operating an operation means (not shown). The set value setting unit 21 changes the set value of the parameter in response to an operation signal input from the operation means. The set value of the parameter being set is displayed on a display device (not shown). The operator changes the set value to the desired value by operating the operation means while looking at the set value displayed on the display device. The parameters of the welding conditions include the welding current, welding voltage, and wire feed speed. The set value setting unit 21 outputs the set value of the welding current to the current control unit 22 as a current command value.

[0037] Fan control unit 23 is a functional component for controlling the operation of each cooling fan 6. Fan control unit 23 operates each cooling fan from the time welding power supply A1 is started until it is stopped. Note that the operation period of each cooling fan 6 is not limited to this. Fan control unit 23 may operate each cooling fan 6 according to the temperature detected by temperature sensor 3 or another temperature sensor (not shown), for example. The operation period may also differ for each cooling fan 6. Furthermore, while each cooling fan 6 is operating, fan control unit 23 obtains the rotation speed from an encoder (not shown) attached to that cooling fan 6. Fan control unit 23 outputs the rotation speed of each cooling fan 6 to abnormality detection unit 24.

[0038] The abnormality detection unit 24 is a functional component for detecting an abnormality in each cooling fan 6. The abnormality detection unit 24 detects an abnormality in each cooling fan 6 based on the rotation speed of each cooling fan 6 input from the fan control unit 23. If the rotation speed of a cooling fan 6 is equal to or lower than a predetermined value, the abnormality detection unit 24 determines that the cooling fan 6 is abnormal. If the abnormality detection unit 24 detects an abnormality in any cooling fan 6, it outputs an abnormality detection signal indicating the detection of the abnormality to the stop control unit 26 and outputs information for identifying the cooling fan 6 in which the abnormality was detected to the grace time setting unit 25. Note that the method by which the abnormality detection unit 24 detects an abnormality is not limited. It is sufficient that the abnormality detection unit 24 detects an abnormality in a cooling fan 6 by some method and output information for identifying the cooling fan 6 in which the abnormality occurred.

[0039] Grace time setting unit 25 is a functional component that sets a grace time until the operation of power conversion unit 1 is stopped when abnormality detection unit 24 detects an abnormality in cooling fan 6. Grace time setting unit 25 receives information from abnormality detection unit 24 for identifying cooling fan 6 in which an abnormality has been detected. When the information is received from abnormality detection unit 24, grace time setting unit 25 acquires the current value of the output current of welding power supply A1 (power conversion unit 1) based on the current detection signal received from output current sensor 71. Grace time setting unit 25 also acquires the voltage value of the output voltage of welding power supply A1 (power conversion unit 1) based on the voltage detection signal received from output voltage sensor 72. Grace time setting unit 25 also acquires the detected temperature value of the internal temperature based on the temperature detection signal received from temperature sensor 3. Grace time setting unit 25 sets the grace time based on the acquired information. In this embodiment, the grace time setting unit 25 reads out the corresponding grace time by referring to the grace time table stored in the storage unit 4. The grace time setting unit 25 outputs the set grace time to the stop control unit 26.

[0040] The information used by grace time setting unit 25 to set the grace time is not limited to the information described above. Grace time setting unit 25 may set the grace time using part of the information described above. For example, if welding power supply A1 is equipped with only one cooling fan 6, information identifying the cooling fan 6 in which an abnormality has occurred is not necessary. Grace time setting unit 25 may set the grace time without using any of the current value of the output current, the voltage value of the output voltage, and the detected internal temperature. Grace time setting unit 25 may also set the grace time using information other than the information described above. The information used may be information that detects the magnitude of a temperature rise factor, which is a factor that increases the temperature of the components of power conversion unit 1.

[0041] The stop control unit 26 is a functional component for stopping the operation of the power conversion unit 1. The stop control unit 26 outputs a stop signal to the current control unit 22 when the grace time input by the grace time setting unit 25 has elapsed since the abnormality detection signal was input from the abnormality detection unit 24. When the stop signal is input from the stop control unit 26, the current control unit 22 stops outputting the drive signal. This causes the operation of the power conversion unit 1 to stop, and therefore the output. Furthermore, when the abnormality detection signal is input from the abnormality detection unit 24, the stop control unit 26 outputs a stop notification command to the notification control unit 27, which is a command to notify the notification control unit 27 that the operation of the power conversion unit 1 should be stopped.

[0042] The notification control unit 27 is a functional configuration for causing the notification unit 5 to issue a notification. When a stop notification command is input from the stop control unit 26, the notification control unit 27 causes the notification unit 5 to notify that the operation of the power conversion unit 1 will be stopped. If the notification unit 5 includes a light-emitting unit, the notification control unit 27, for example, causes the light-emitting unit to flash in a predetermined light color (for example, yellow). If the notification unit 5 includes a display device, the notification control unit 27, for example, causes the display device to display a warning such as "Operation will soon be stopped." In this case, the notification control unit 27 may display the time remaining until the stop and count down the time. If the notification unit 5 includes a speaker, the notification control unit 27 may issue a warning such as "Operation will soon be stopped" by voice. The manner of notification is not limited.

[0043] 3 is an example of a flowchart showing the abnormality determination process performed by the control unit 2. The abnormality determination process is executed at each predetermined timing.

[0044] First, it is determined whether or not an abnormality has been detected in the cooling fans 6 (S1). Specifically, the abnormality detection unit 24 detects an abnormality in each cooling fan 6 based on the rotation speed of each cooling fan 6 input from the fan control unit 23. If no abnormality has been detected (S1: NO), the abnormality determination process ends.

[0045] On the other hand, if an abnormality is detected (S1: YES), various pieces of information are acquired (S2). Specifically, the grace time setting unit 25 acquires information for identifying the cooling fan 6 in which the abnormality has been detected from the abnormality detection unit 24, and acquires the detected temperature value of the internal temperature based on the temperature detection signal input from the temperature sensor 3. The grace time setting unit 25 also acquires the current value of the output current based on the current detection signal input from the output current sensor 71, and acquires the voltage value of the output voltage based on the voltage detection signal input from the output voltage sensor 72. Next, the grace time is read out based on this information (S3). Specifically, the grace time setting unit 25 refers to a grace time table stored in the storage unit 4 and reads out the corresponding grace time based on the acquired information.

[0046] Next, a warning is issued to indicate that the operation of the power conversion unit 1 will be stopped (S4). Specifically, the stop control unit 26 outputs a stop notification command to the notification control unit 27. The notification control unit 27, which has received the stop notification command, causes the notification unit 5 to issue a warning.

[0047] Next, it is determined whether or not a grace period has elapsed since the abnormality was detected (S5). If the grace period has not elapsed (S5: NO), the process returns to step S5 and the determination is repeated. If the grace period has elapsed (S5: YES), the operation of the power conversion unit 1 is stopped (S6), and the abnormality determination process ends. Specifically, when the grace period has elapsed since the abnormality was detected, the stop control unit 26 outputs a stop signal to the current control unit 22. The current control unit 22 that has received the stop signal stops outputting the drive signal. This causes the power conversion unit 1 to stop operating, and therefore the output is stopped.

[0048] The process shown in the flowchart of FIG. 3 is an example, and the abnormal stop process performed by the control unit 2 is not limited to the above.

[0049] Next, the effects of the welding power supply A1 will be described.

[0050] According to this embodiment, when the control unit 2 detects an abnormality in the cooling fan 6, it stops the operation of the power conversion unit 1 after the grace period has elapsed. The grace period is set appropriately depending on the state of each cooling fan 6, the internal temperature, the output current, and the output voltage. This reduces the possibility that the temperature of a heat-generating component will rise too much and be damaged between the time when an abnormality in the cooling fan 6 is detected and the time when the grace period has elapsed. In addition, there is no need to provide a temperature sensor for each heat-generating component. This allows the welding power supply A1 to appropriately stop output when an abnormality occurs in the cooling fan 6 before the component is damaged by heat, without using multiple temperature sensors.

[0051] Furthermore, in this embodiment, the grace period is associated with the state of each cooling fan 6, the internal temperature, the output current, and the output voltage, and is stored in the storage unit 4 as a grace period table. Therefore, the grace period setting unit 25 can easily set the grace period based on the acquired information. Furthermore, since the grace period is set based on the internal temperature, the output current, and the output voltage, which are related to the temperature rise of each component, an appropriate period is set. Furthermore, since the grace period is set based on which cooling fan 6 has experienced an abnormality, a more appropriate period is set.

[0052] Furthermore, according to this embodiment, the abnormality detection unit 24 detects an abnormality in each cooling fan 6 based on the rotation speed of each cooling fan 6. Therefore, the abnormality detection unit 24 can appropriately detect an abnormality in each cooling fan 6.

[0053] Furthermore, in this embodiment, when stop control unit 26 receives an abnormality detection signal from abnormality detection unit 24, it outputs a stop notification command to notification control unit 27, causing notification unit 5 to notify that the operation of power conversion unit 1 will be stopped. This allows the operator of welding power supply A1 to know in advance that the operation of power conversion unit 1 will be stopped. Therefore, the operator can end welding before the output of welding power supply A1 is stopped. In this way, welding power supply A1 can prevent the welding operation from suddenly stopping.

[0054] In the present embodiment, the grace time setting unit 25 reads out the grace time by referring to the grace time table stored in the storage unit 4, but this is not limiting. The grace time setting unit 25 may calculate the grace time based on a predetermined arithmetic expression using the acquired information. For example, the grace time setting unit 25 may select an arithmetic expression depending on the state (normal or abnormal) of each cooling fan 6, and calculate the grace time based on the selected arithmetic expression using the current value of the output current, the voltage value of the output voltage, and the detected temperature value of the internal temperature of the device.

[0055] Furthermore, in the present embodiment, the case where the fan control unit 23 controls the operation of each cooling fan 6 has been described, but this is not limiting. The fan control unit 23 may change the airflow volume in multiple stages by controlling the rotation speed of each cooling fan 6. In this case, the abnormality detection unit 24 may determine that the cooling fan 6 is abnormal if the difference between the rotation speed of the cooling fan 6 and the set rotation speed is equal to or greater than a predetermined value.

[0056] In addition, in this embodiment, the case where control unit 2 performs current control has been described, but this is not limiting. Control unit 2 may also perform voltage control. In this case, control unit 2 generates a drive signal based on the difference between a voltage command value and a voltage value corresponding to a voltage detection signal that detects the output voltage of welding power supply A1.

[0057] In addition, in this embodiment, the case where welding power supply A1 outputs DC power has been described, but this is not limiting. Welding power supply A1 may also be provided with an inverter between power conversion unit 1 and the output terminal to output AC power.

[0058] In this embodiment, the grace period is set based on which cooling fan 6 has an abnormality. However, the grace period also varies depending on the degree of abnormality (whether the cooling fan 6 has completely stopped or is rotating slowly). FIG. 4 shows an example of a modified first table of the grace period table. In this modified example, the degree of abnormality is taken into consideration, and different second tables are referenced depending on whether the cooling fan 6 has an abnormality where it has completely stopped or where its rotation is slowing down. For example, even if only the first fan (cooling fan 61) is abnormal, if the abnormality is where the rotation is slowing down, the corresponding second table, "Table 11," is referenced, and if the abnormality is where the cooling fan 6 has completely stopped, the corresponding second table, "Table 12," is referenced. Furthermore, if only the third fan (cooling fan 63) is normal, there are four patterns depending on the degree of abnormality of the other cooling fans 6, and Tables 21 to 24 are associated with each of them. If all cooling fans 6 are abnormal, there are eight patterns depending on the degree of abnormality of each cooling fan 6, and Tables 31 to 38 are associated with each of them.

[0059] In this modification, the abnormality detection unit 24 also detects the degree of abnormality of each cooling fan 6 based on the rotation speed of each cooling fan 6 input from the fan control unit 23. If the rotation speed of a cooling fan 6 is equal to or less than a first predetermined value close to "0", the abnormality detection unit 24 determines that the cooling fan 6 is completely stopped, which is an abnormality. Furthermore, if the rotation speed of a cooling fan 6 is greater than the first predetermined value and equal to or less than a second predetermined value (> first predetermined value), the abnormality detection unit 24 determines that the cooling fan 6 is rotating too slowly, which is an abnormality. According to this modification, a more appropriate grace period can be set. Note that, although the degree of abnormality is detected in two stages in the above, this is not limited to this, and detection may be performed in three or more stages.

[0060] Second Embodiment FIG. 5 is a block diagram illustrating the internal configuration of a welding power supply A2 according to a second embodiment. In FIG. 5, elements that are the same as or similar to those in the above embodiment are given the same reference numerals, and redundant explanations will be omitted. The welding power supply A2 according to this embodiment differs from the welding power supply A1 according to the first embodiment in that the input voltage of the power conversion unit 1 is used to set the grace time. The configuration and operation of other parts of this embodiment are the same as those of the first embodiment.

[0061] Welding power supply A2 according to the second embodiment further includes input voltage sensor 73. Input voltage sensor 73 detects the input voltage of welding power supply A1 (power conversion unit 1). In this embodiment, input voltage sensor 73 detects the three-phase AC voltage on the input side of power conversion unit 1 to detect the input voltage. Input voltage sensor 73 outputs an input voltage detection signal corresponding to the input voltage to control unit 2.

[0062] In the second embodiment, the second table of the grace time table stores the correspondence between the input voltage and the on-board temperature, output current, and output voltage. Furthermore, when information is input from the abnormality detection unit 24, the grace time setting unit 25 according to the second embodiment acquires the voltage value of the input voltage of the welding power supply A1 (power conversion unit 1) based on the input voltage detection signal input from the input voltage sensor 73. The grace time setting unit 25 references the grace time table stored in the memory unit 4 and reads out the corresponding grace time using the acquired current value of the output current, voltage value of the output voltage, detected on-board temperature, and voltage value of the input voltage. The higher the input voltage of the welding power supply A1 (power conversion unit 1), the more heat is generated by the switching elements 11, reactor 13, and transformer of the inverter circuit. Therefore, the grace time can be set more appropriately by taking the input voltage into consideration.

[0063] This embodiment can also achieve the same effects as the first embodiment. Furthermore, according to this embodiment, grace time setting unit 25 also uses the acquired voltage value of the input voltage to set the corresponding grace time. Therefore, welding power supply A2 can set the grace time more appropriately than when the input voltage is not taken into consideration. As can be seen from this embodiment, the information used by grace time setting unit 25 to set the grace time is not limited. It is sufficient that the information used is information that detects the magnitude of a temperature rise factor, which is a factor that raises the temperature of the components of power conversion unit 1. Other possible temperature rise factors include the input current of power conversion unit 1 and the frequency (switching frequency) of the drive signal input to each switching element 11 of the inverter circuit.

[0064] Third Embodiment 6 and 7 are diagrams illustrating a welding power supply A3 according to a third embodiment. FIG. 6(a) is a block diagram illustrating the internal configuration of the welding power supply A3. FIG. 6(b) is a simplified diagram illustrating an example of the interior of the housing 9 of the welding power supply A3. FIG. 7 is an example of a flowchart illustrating an abnormality determination process according to the third embodiment. In these figures, elements that are the same as or similar to those in the above embodiment are given the same reference numerals as in the above embodiment, and redundant explanations will be omitted. The welding power supply A3 according to this embodiment differs from the welding power supply A1 according to the first embodiment in that it further includes a temperature sensor 35 that detects the temperature of the switching element 11. The configuration and operation of other parts of this embodiment are the same as those of the first embodiment.

[0065] The welding power supply A3 according to the third embodiment further includes a temperature sensor 35. The temperature sensor 35 is, for example, a thermistor, and detects the temperature of the switching element 11. Note that the temperature sensor 35 is not limited to a thermistor and may be other sensors. The temperature sensor 35 is disposed in a position where it can detect the temperature of the switching element 11. Although a simplified illustration is shown in FIG. 6(b), the temperature sensor 35 is mounted, for example, at a position on a substrate on which a plurality of switching elements 11 are mounted, at an equal distance from each of the switching elements 11. Note that the position where the temperature sensor 35 is disposed is not limited. The temperature sensor 35 outputs a temperature detection signal corresponding to the detected temperature to the control unit 2.

[0066] The stop control unit 26 according to the third embodiment acquires the temperature of the switching element 11 based on a temperature detection signal input from the temperature sensor 35. If the acquired temperature is equal to or higher than a predetermined temperature, the stop control unit 26 outputs a stop signal to the current control unit 22. When the stop signal is input from the stop control unit 26, the current control unit 22 stops outputting the drive signal. This causes the power conversion unit 1 to stop operating, and output is therefore stopped. At the same time, the stop control unit 26 outputs a temperature abnormality notification command to the notification control unit 27, which is a command to notify the notification control unit 27 that a temperature abnormality has occurred. When the temperature abnormality notification command is input from the stop control unit 26, the notification control unit 27 causes the notification unit 5 to notify that the operation of the power conversion unit 1 has been stopped due to the occurrence of a temperature abnormality.

[0067] As shown in Fig. 7, in the abnormality determination process according to the third embodiment, step S11 is added before step S1, and step S12 is added before step S5. In the abnormality determination process, first, it is determined whether or not a temperature abnormality has been detected (S11). Specifically, the stop control unit 26 determines whether or not the acquired temperature is equal to or higher than a predetermined temperature. If a temperature abnormality has been detected (S11: YES), the process proceeds to step S6, where the operation of the power conversion unit 1 is stopped (S6), and the abnormality determination process ends. On the other hand, if a temperature abnormality has not been detected (S11: NO), the process proceeds to step S1, where it is determined whether or not an abnormality has been detected in the cooling fan 6 (S1).

[0068] Also, while waiting for the grace period to elapse in step S5, it is determined whether or not a temperature abnormality has been detected (S12). If a temperature abnormality has been detected (S12: YES), the process proceeds to step S6, where the operation of the power conversion unit 1 is stopped (S6), and the abnormality determination process ends. On the other hand, if a temperature abnormality has not been detected (S12: NO), the process proceeds to step S5, where it is determined whether or not the grace period has elapsed (S5). In other words, the determinations in steps S12 and S5 are repeated until a temperature abnormality is detected or the grace period has elapsed. Note that the process shown in the flowchart of FIG. 7 is an example, and the abnormality stop process performed by the control unit 2 is not limited to the one described above.

[0069] This embodiment can also achieve the same effects as the first embodiment. Furthermore, according to this embodiment, if the temperature of switching element 11 rises suddenly and exceeds a predetermined temperature, power conversion unit 1 stops operating and output is stopped. Therefore, welding power supply A3 can prevent switching element 11 from being damaged even if the temperature of switching element 11 rises suddenly before the grace period has elapsed.

[0070] In the third embodiment, the temperature sensor 35 detects the temperature of the switching element 11, but this is not limiting. The temperature sensor 35 may detect the temperature of other components.

[0071] In the first to third embodiments, the present invention has been described as being applied to a welding power supply, but is not limited to this. The present invention can also be applied to thermal processing power supply devices for processes other than welding. For example, the present invention can be applied to thermal processing power supply devices that supply power to a plasma cutting system that generates plasma at the tip of a torch to cut a workpiece W, or an air arc gouging system that digs grooves by using the heat of an arc generated at the tip of a torch and a jet of compressed air.

[0072] The thermal processing power supply device according to the present invention is not limited to the above-described embodiment, and the specific configuration of each part of the thermal processing power supply device according to the present invention can be freely designed and modified in various ways. [Explanation of symbols]

[0073] A1 to A3: welding power supply, 1: power conversion unit, 2: control unit, 3: temperature sensor, 5: alarm unit, 6: cooling fan, 71: output current sensor, 72: output voltage sensor, 73: input voltage sensor, 9: housing

Claims

1. A power conversion unit that converts the input power into power for hot processing, A control unit that controls the power conversion unit, A housing that houses the power conversion unit and the control unit, At least one cooling fan that cools the inside of the housing, A detection unit that detects the size of a temperature-rising element, which is an element that raises the temperature of the components of the power conversion unit, Comprising, When the control unit detects an abnormality in the cooling fan, it sets a grace period corresponding to the value detected by the detection unit, and stops the operation of the power conversion unit when the grace period has elapsed. A power supply device for hot processing.

2. The detection unit includes an output current sensor that detects the output current of the power conversion unit, an output voltage sensor that detects the output voltage of the power conversion unit, and a temperature sensor that detects the in-machine temperature, which is the ambient temperature inside the housing. The control unit sets the grace period based on the output current value detected by the output current sensor, the output voltage value detected by the output voltage sensor, and the temperature detection value detected by the temperature sensor. The power supply device for hot processing according to Claim 1.

3. The detection unit further includes an input voltage sensor that detects the input voltage of the power conversion unit. The control unit further sets the grace period based on the input voltage value detected by the input voltage sensor. The power supply device for hot processing according to Claim 2.

4. There are a plurality of the cooling fans. The control unit further sets the grace period based on which cooling fan has an abnormality. The power supply device for hot processing according to any one of Claims 1 to 3.

5. When the control unit detects an abnormality in the cooling fan, it further includes a notification unit that notifies that the operation of the power conversion unit is stopped. The power supply device for hot processing according to Claim 1.

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