Welding device

Abstract

To provide a welding device that can properly perform feedback control even if a current detection part deteriorates over time.SOLUTION: A welding device A1 supplies an electric current to a welding load. The welding device A1 comprises: a conversion part (transformer TNT and so on) which converts an inputted current and outputs the same; a first detection component 11 which detects an input current to the conversion part; a second detection component 21 which detects an output current of the conversion part; and a correction part 22 which corrects a detection signal of the second detection component 21, and outputs the detection signal after correction. The correction part 22 corrects a detection signal of the second detection component 21 so that a ratio of a second detection value of the second detection component 21 to a first detection value of the first detection component 11 becomes constant.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to welding equipment. [Background technology]

[0002] Conventionally, welding devices perform feedback control to maintain the welding current at a set value. Patent Document 1 discloses an example of a welding device that performs feedback control. The welding device described in Patent Document 1 detects the welding current value using a current detection unit, compares the detected current value with a set current value, and performs feedback control so that the welding current value becomes the set current value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6417545 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional welding equipment, the current detector that detects the welding current uses, for example, a current transformer (CT) or a Hall current detector. The current detector may deteriorate over time depending on the duration of use, the environment in which the welding equipment is used, and its intended use. For example, a resistor built into the current detector may become corroded by sulfide substances, resulting in an increased resistance. Such deterioration over time can prevent the detection of an appropriate current value, resulting in a discrepancy between the actual current value and the detected value. Performing feedback control in this state may result in the welding current not being able to be controlled to the set current. This can result in problems such as an unstable arc, no arc, adhesion between the welding electrode (e.g., welding wire or welding rod) and the workpiece, or no high-frequency power being output during TIG welding.

[0005] The present disclosure has been devised in consideration of the above circumstances, and its purpose is to provide a welding device that can perform feedback control appropriately even if the current detection unit deteriorates over time. [Means for solving the problem]

[0006] The welding apparatus provided by the present disclosure is a welding apparatus that supplies current to a welding load, and includes a conversion unit that converts and outputs the input current, a first detection component that detects the input current to the conversion unit, a second detection component that detects the output current of the conversion unit, and a correction unit that corrects the detection signal of the second detection component and outputs the corrected detection signal, wherein the correction unit corrects the detection signal of the second detection component so that the ratio of the second detection value of the second detection component to the first detection value of the first detection component is constant.

[0007] In a preferred embodiment of the welding device, the correction unit includes a ratio calculation unit that calculates an initial ratio, which is the ratio at a first point in time prior to the present time; a correction value calculation unit that calculates a correction value for correcting the detection signal of the second detection component using the initial ratio; and an output unit that corrects the detection signal of the second detection component with the correction value and outputs the detection signal.

[0008] In a preferred embodiment of the welding device, the initial ratio includes a plurality of values ​​depending on the state of the welding load, and the correction value calculation unit changes the value of the initial ratio to be used depending on the state of the welding load.

[0009] In a preferred embodiment of the welding device, the initial ratio includes a plurality of values ​​depending on an internal temperature of the welding device, and the correction value calculation unit changes the value of the initial ratio to be used depending on the internal temperature.

[0010] In a preferred embodiment of the welding device, the correction unit includes a memory unit that stores the correction value calculated by the correction value calculation unit, and the output unit corrects the detection signal of the second detection component using an average value of the multiple correction values ​​stored in the memory unit.

[0011] In a preferred embodiment of the welding device, the welding device further includes an inverter circuit that inputs a current to the conversion unit, and a control unit that receives the corrected detection signal from the correction unit and controls the inverter circuit using the corrected detection signal. [Effects of the Invention]

[0012] In the welding device of the present disclosure, the correction unit corrects the detection signal of the second detection component so that the ratio of the second detection value of the second detection component to the first detection value of the first detection component is constant. With this configuration, the second detection value of the second detection component is corrected according to the first detection value of the first detection component. Therefore, even if a discrepancy occurs between the current value actually flowing through the location where the second detection component is installed on the secondary side of the conversion unit (transformer INT) and the second detection value of the second detection component due to aging of the second detection component, the correction unit outputs a detection signal in which the discrepancy is suppressed. Therefore, with the welding device of the present disclosure, feedback control can be performed appropriately even if the current detection unit (second detection component) has deteriorated over time. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a block diagram showing an example of the configuration of a welding device according to a first embodiment; [Figure 2] FIG. 10 is a block diagram showing an example of the configuration of a welding device according to a second embodiment. [Figure 3] FIG. 10 is a diagram showing an example of an initial ratio stored in a storage unit of a correction unit of a welding device according to a second embodiment. [Figure 4] FIG. 10 is a block diagram showing an example of the configuration of a welding device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the welding device of the present disclosure will be described below with reference to the drawings. In the following, identical or similar components will be designated by the same reference numerals, and redundant description will be omitted.

[0015] 1 shows a welding device A1 according to a first embodiment. The welding device A1 generates an arc between a welding electrode B and a workpiece W and supplies power to the arc. The welding electrode B, the workpiece W, and the generated arc together constitute the load on the welding device A1, and so this combination is referred to as the "welding load." Note that the welding device A1 is not limited to a welder that performs arc welding.

[0016] As shown in FIG. 1, the welding device A1 includes a rectifying and smoothing circuit DR1, an inverter circuit INV, a transformer INT, a rectifying and smoothing circuit DR2, an input side detector 1, an output side detector 2, and a controller 3.

[0017] The rectifying and smoothing circuit DR1 converts AC power input from a commercial power source P into DC power and outputs it. The rectifying and smoothing circuit DR1 includes a rectifying circuit that rectifies the AC current and a smoothing circuit (e.g., a smoothing capacitor) that smoothes the output of the rectifying circuit. The configuration of the rectifying and smoothing circuit DR1 is not limited.

[0018] The inverter circuit INV is, for example, a single-phase full-bridge PWM-controlled inverter having four switching elements. The inverter circuit INV converts the DC power input from the rectifying and smoothing circuit DR1 into high-frequency AC power and outputs it by switching the four switching elements in response to an output control drive signal input from the control unit 3. Note that the inverter circuit INV may be any circuit that converts DC power into high-frequency power, and may be, for example, a half-bridge type having two switching elements, or an inverter circuit with another configuration.

[0019] The transformer INT transforms the high-frequency voltage output by the inverter circuit INV and outputs it to the rectifying and smoothing circuit DR2. The transformer INT includes a primary winding L1 and a secondary winding L2. The primary winding L1 has input terminals that are individually connected to the output terminals of the inverter circuit INV, and receives the high-frequency voltage from the inverter circuit INV. The secondary winding L2 has output terminals that are individually connected to the input terminals of the rectifying and smoothing circuit DR2, and outputs the transformed high-frequency voltage. The output voltage of the inverter circuit INV is transformed in accordance with the ratio (turns ratio) between the number of turns N1 of the primary winding L1 and the number of turns N2 of the secondary winding L2, and is output to the rectifying and smoothing circuit DR2.

[0020] The rectifying and smoothing circuit DR2 converts the high-frequency power input from the transformer INT into DC power and outputs it. The rectifying and smoothing circuit DR2 includes a rectifying circuit that rectifies the high-frequency current and a smoothing circuit (e.g., a smoothing reactor) that smoothes the output of the rectifying circuit. The configuration of the rectifying and smoothing circuit DR2 is not limited. One of the output terminals of the rectifying and smoothing circuit DR2 is connected to the welding electrode B, and the other output terminal of the rectifying and smoothing circuit DR2 is connected to the workpiece W. When the welding device A1 performs AC welding, an inverter circuit that performs DC-AC conversion is provided downstream of the rectifying and smoothing circuit DR2.

[0021] In the welding device A1, a magnetic field is generated by the current (AC current) flowing through the primary winding L1 of the transformer INT, and an induced electromotive force due to this magnetic field is generated in the secondary winding L2 of the transformer INT. This induced electromotive force causes a current to flow through the secondary winding L2. At this time, voltage conversion and current conversion are performed between the primary winding L1 and the secondary winding L2. After that, the high-frequency current is rectified to DC current in the rectifying and smoothing circuit DR2. Therefore, in this embodiment, the combination of the transformer INT and the rectifying and smoothing circuit DR2 is an example of a conversion unit that converts and outputs an input current.

[0022] The input side detector 1 detects the input current (primary side current) input to the primary winding L1, which is the current on the primary side of the transformer INT. A detection signal from the input side detector 1 is output to the output side detector 2. The input side detector 1 includes a first detection component 11, as shown in FIG.

[0023] The first detection component 11 is installed on a line 91 connecting the inverter circuit INV and the primary winding L1 of the transformer INT. The first detection component 11 outputs a detection signal corresponding to the current (input current) flowing through the line 91. Hereinafter, the detection signal output by the first detection component 11 will be referred to as a "primary-side current detection signal." The first detection component 11 is configured, for example, by a CT (instrument current transformer). The first detection component 11 may be configured by a Hall element instead of a CT. In this embodiment, the primary-side current detection signal of the first detection component 11 is output to the output-side detection unit 2 as the detection signal of the input-side detection unit 1. The input-side detection unit 1 may output the output (primary-side current detection signal) of the first detection component 11 to the output-side detection unit 2 as an analog signal, or may convert the output (primary-side current detection signal) of the first detection component 11 to a digital signal using an AD converter (not shown) and then output it to the output-side detection unit 2.

[0024] The output-side detector 2 detects the output current (secondary-side current) of the rectifying and smoothing circuit DR2, which is the current on the secondary side of the transformer INT. The output current of the rectifying and smoothing circuit DR2 is the output current (welding current) of the welding device A1. The output-side detector 2 includes a current detector using, for example, a Hall element. As shown in FIG. 1, the output-side detector 2 includes a second detection component 21 and a correction unit 22.

[0025] The second detection component 21 is installed on a line 93 electrically connected between the rectifying and smoothing circuit DR2 and the welding load. In this embodiment, the line 93 connects the rectifying and smoothing circuit DR2 and the workpiece W. Unlike the example shown in FIG. 1 , the second detection component 21 may be installed on a line connecting the rectifying and smoothing circuit DR2 and the welding electrode B, or on a line connecting the secondary winding L2 and the rectifying and smoothing circuit DR2. The second detection component 21 outputs a detection signal corresponding to the current (output current) flowing through the line 93 to the correction unit 22. Hereinafter, the detection signal output by the second detection component 21 will be referred to as a "secondary-side current detection signal." A state in which a current flows through the line 93 will be referred to as a "powered state," and a state in which no current flows through the line 93 will be referred to as a "powered state." The second detection component 21 is, for example, a Hall element, and detects a magnetic field generated by the current flowing through the line 93 and outputs a voltage signal as the secondary-side current detection signal. Second detection component 21 may be another current sensor such as a CT (instrument current transformer) instead of a Hall element. Note that output-side detection unit 2 may output the output (secondary-side current detection signal) of second detection component 21 to correction unit 22 as an analog signal, or may convert the output into a digital signal by an AD converter (not shown) and then output it to correction unit 22.

[0026] The correction unit 22 corrects the secondary-side current detection signal of the second detection component 21 so that the ratio (second detection value / first detection value) of the second detection value of the second detection component 21 to the first detection value of the first detection component 11 is constant. The first detection value is a value corresponding to the primary-side current detection signal of the first detection component 11, and the second detection value is a value corresponding to the secondary-side current detection signal of the second detection component 21. The correction unit 22 outputs the corrected secondary-side current detection signal to the control unit 3. As shown in FIG. 1 , the correction unit 22 includes a ratio calculation unit 221, a storage unit 222, a correction value calculation unit 223, and an output unit 224.

[0027] The ratio calculation unit 221 calculates the ratio of the second detection value of the second detection component 21 to the first detection value of the first detection component 11. In this embodiment, the ratio calculation unit 221 calculates the ratio at a first time point prior to the present time. Hereinafter, this ratio will be referred to as the "initial ratio." In this embodiment, the first time point is the time of shipment (shipment inspection) of the welding device A1. That is, the initial ratio in this embodiment is the ratio (the ratio of the second detection value to the first detection value) at the time of shipment (shipment inspection) of the welding device A1. For example, an electrical current inspection is performed during the shipping inspection of the welding device A1, and the ratio calculation unit 221 calculates the initial ratio using the first detection value of the first detection component 11 and the second detection value of the second detection component 21 when electrical current is applied during this electrical current inspection. At this time, the initial ratio is calculated using the first detection value when the second detection value is a predetermined value. Unlike this example, the initial ratio may be calculated using the second detection value when the first detection value is a predetermined value. The calculated initial ratio is then stored in the storage unit 222. Note that the first point in time is not limited to the time of shipment, as long as it is a point in time prior to the present time. For example, the first point in time may be when the second detection component 21 is replaced, or when an inspection button (not shown) is operated.

[0028] The storage unit 222 is configured by, for example, a memory, etc. The storage unit 222 stores the initial ratio Kzz calculated by the ratio calculation unit 221.

[0029] The correction value calculation unit 223 calculates a correction value for correcting the detection signal (secondary-side current detection signal) of the second detection component 21 using the initial ratio stored in the storage unit 222. The primary-side current detection signal of the first detection component 11 and the secondary-side current detection signal of the second detection component 21 are input to the correction value calculation unit 223. The correction value calculation unit 223 calculates a first detection value from the input primary-side current detection signal and calculates a second detection value from the input secondary-side current detection signal. Then, the correction value calculation unit 223 multiplies the first detection value by the initial ratio and subtracts the second detection value from the multiplied value. The correction value calculation unit 223 calculates this subtracted value as the correction value. That is, the correction value calculation unit 223 calculates the correction value by calculating ((Idet1 × Kzz) - Idet2) where Idet1 is the first detection value, Idet2 is the second detection value, and Kzz is the initial ratio. The correction value calculation unit 223 outputs a correction signal according to the calculated correction value to the output unit 224.

[0030] The output unit 224 receives the secondary-side current detection signal from the second detection component 21 and the correction signal from the correction value calculation unit 223. The output unit 224 corrects the input secondary-side current detection signal using the input correction signal. For example, the output unit 224 is configured with an adder circuit, and adds the correction signal to the input secondary-side current detection signal. The output unit 224 outputs this added signal to the control unit 3 as the corrected secondary-side current detection signal.

[0031] Setting unit 4 performs various settings for welding device A1. For example, setting unit 4 sets the output current (welding current) and the output voltage (welding voltage) as the welding output settings. For example, when a user of welding device A1 operates an operation unit (not shown) to specify the output current and output voltage, setting unit 4 sets the specified output current and output voltage. Setting unit 4 outputs the set welding output setting values ​​(the respective setting values ​​of the output current and output voltage) to control unit 3.

[0032] Control unit 3 controls inverter circuit INV based on the set values ​​of welding output (set values ​​of output current and output voltage) input from setting unit 4. For example, control unit 3 performs feedback control of the output current of welding device A1. Control unit 3 generates an output control drive signal for controlling the switching element of inverter circuit INV by PWM control based on the deviation between the detected value of the output current (welding current) of welding device A1 (i.e., the output of output-side detection unit 2, which is the corrected secondary-side current detection signal) and the set value of the output current. Control unit 3 outputs the generated output control drive signal to inverter circuit INV.

[0033] The welding device A1 configured as above has the following functions and effects.

[0034] The welding device A1 includes a transformer INT, a rectifying and smoothing circuit DR2, a first detection component 11, a second detection component 21, and a correction unit 22. The transformer INT transforms an input voltage and outputs it. During this transformation, the transformer INT converts the input current and outputs it. The rectifying and smoothing circuit DR2 rectifies and smooths the output current (high-frequency current) of the transformer INT and outputs it. In other words, the transformer INT and the rectifying and smoothing circuit DR2 function as a conversion unit that converts and outputs the input current. The first detection component 11 detects the input current (primary-side current) to the conversion unit (transformer INT). The second detection component 21 detects the output current (secondary-side current) of the conversion unit (rectifying and smoothing circuit DR2). The correction unit 22 corrects the detection signal (secondary-side current detection signal) of the second detection component 21 so that the ratio of the second detection value of the second detection component 21 to the first detection value of the first detection component 11 is constant. According to this configuration, the second detection value of second detection component 21 is corrected in accordance with the first detection value of first detection component 11. Therefore, even if a deviation occurs between the value of the current actually flowing at the installation location of second detection component 21 on the secondary side of the conversion unit (transformer INT) and the second detection value of second detection component 21 due to aging deterioration of second detection component 21, correction unit 22 outputs a detection signal (secondary-side current detection signal) in which the deviation is suppressed. Therefore, even if second detection component 21 has deteriorated over time, welding device A1 can use the corrected secondary-side current detection signal of second detection component 21, thereby enabling appropriate feedback control of the welding output.

[0035] The welding device A1 includes an inverter circuit INV that inputs current to a conversion unit (transformer INT in this embodiment) and a control unit 3 that controls the inverter circuit INV using a corrected secondary-side current detection signal from a correction unit 22. When the inverter circuit INV is controlled by such feedback control, a second detection component 21 that detects the secondary-side current (output current) is provided. If the detection accuracy of the second detection component 21 decreases due to aging of the second detection component 21, the welding quality (e.g., the bead cross section) may gradually deteriorate. For this reason, the welding quality may be suppressed by adjusting the set current based on the skill and intuition of the welding operator. Manual adjustment of the set current by the welding operator may result in a long-term stoppage of the production line, resulting in a decrease in productivity. In contrast, the welding device A1 corrects the second detection value (secondary-side current detection signal) of the second detection component 21 even if the second detection component 21 deteriorates over time, eliminating the need for manual adjustment of the set current by the welding operator. Therefore, the welding device A1 can suppress a decrease in productivity.

[0036] In the welding device A1, the correction unit 22 includes a ratio calculation unit 221 that calculates a ratio (initial ratio) at a first time point prior to the present time, a correction value calculation unit 223 that calculates a correction value for correcting the secondary-side current detection signal of the second detection component 21 using the initial ratio, and an output unit 224 that corrects the secondary-side current detection signal of the second detection component 21 with the correction value and outputs the corrected signal. In this configuration, the secondary-side current detection signal of the second detection component 21 is corrected so that the ratio at the present time becomes the ratio at the first time point. Therefore, the secondary-side current detection signal of the second detection component 21 can be corrected to a secondary-side current detection signal in a state where deterioration over time is less advanced than at the present time. In particular, in the welding device A1, the first time point is the time of shipment of the welding device A1. Therefore, in the welding device A1, deviation of the secondary-side current detection signal (corrected secondary-side current detection signal) output from the correction unit 22 from the shipping state before deterioration of the second detection component 21 over time is suppressed. That is, the welding device A1 can maintain the detection accuracy at the same level as when it was shipped from the factory before the second detection component 21 deteriorated over time.

[0037] In the welding device A1, the first detection component 11 is a CT (instrument current transformer), and the second detection component 21 is a current detector (Hall current detector) that uses a Hall element. Hall current detectors are more susceptible to the effects of aging (e.g., increased internal resistance) than CTs, and do not have very high detection accuracy. Therefore, by correcting the second detection signal of the second detection component 21, which is a Hall current detector, the welding output of the welding device A1 can be stabilized.

[0038] 2 shows a welding device A2 according to a second embodiment. Welding device A2 differs from welding device A1 in that it includes a voltage sensor 41 and a temperature sensor 42, and in that memory unit 222 stores initial ratios of multiple values.

[0039] The voltage sensor 41 detects the output voltage (secondary side voltage) of the welding device A2. The voltage sensor 41 is connected to a pair of output terminals of the rectifying and smoothing circuit DR2. The voltage sensor 41 outputs a detection signal (secondary side voltage detection signal) corresponding to the secondary side voltage to the correction unit 22.

[0040] Temperature sensor 42 is disposed inside welding device A2 and detects the internal temperature of welding device A2. The location of temperature sensor 42 is not limited as long as it is inside welding device A2, but may be disposed, for example, near transformer INT and rectifying smoothing circuit DR2.

[0041] In the welding device A2, the initial ratio includes multiple values ​​depending on predetermined conditions. The conditions in this embodiment include the resistance value of the welding load and the internal temperature of the welding device A2. In this example, multiple values ​​of the initial ratio are stored in the memory unit 222 for each combination of the resistance value of the welding load and the internal temperature of the welding device A2. For example, there are 100 combinations of the resistance value of the welding load, varying in 0.001 Ω increments from 0.001 Ω to 0.1 Ω. There are 20 combinations of the internal temperature, varying in 5°C increments from 5°C to 100°C. Therefore, there are 2000 combinations of the resistance value and the internal temperature. Therefore, 2000 initial ratios are stored in the memory unit 222. Note that the lower limit, upper limit, and pitch for the resistance value of the welding load and the lower limit, upper limit, and pitch for the internal temperature are not limited to the above examples.

[0042] Ratio calculation unit 221 calculates each initial ratio according to the resistance value and internal temperature of each welding load in the state at the first point in time (e.g., at the time of shipment) described above, and stores the calculated initial ratio in storage unit 222. The resistance value of the welding load is calculated according to Ohm's law using the second detection value (secondary-side current detection signal) of second detection component 21 and the detection value (secondary-side voltage detection signal) of voltage sensor 41.

[0043] For example, under certain conditions, the first detection value (primary side current) of first detection component 11 is 100 A, the second detection value (secondary side current) of second detection component 21 is 400 A, the detection value (secondary side voltage) of voltage sensor 41 is 40 V, and the detection value (internal temperature) of temperature sensor 42 is 40°C. In this case, ratio calculation unit 221 calculates 4 (=400 A ÷ 100 A) as the initial ratio Kzz(0.1, 40) when the resistance value of the welding load is 0.1 Ω (=40 V ÷ 400 A) and the internal temperature is 40°C, and stores this in memory unit 222. That is, as shown in FIG. 3 , memory unit 222 stores the value 4 as the initial ratio Kzz(0.1, 40) under the condition where the resistance value of the welding load is 0.1 Ω and the internal temperature is 40°C.

[0044] Also, under another condition, the first detection value (primary side current) of first detection component 11 is 100 A, the second detection value (secondary side current) of second detection component 21 is 410 A, the detection value (secondary side voltage) of voltage sensor 41 is 4.1 V, and the detection value (internal temperature) of temperature sensor 42 is 40°C. In this case, ratio calculation unit 221 calculates 4.1 (=410 A ÷ 100 A) as the initial ratio Kzz(0.01, 40) when the resistance value of the welding load is 0.01 Ω (=4.1 V ÷ 410 A) and the internal temperature is 40°C, and stores this in memory unit 222. That is, as shown in FIG. 3, memory unit 222 stores the value 4.1 as the initial ratio Kzz(0.01, 40) under the condition that the resistance of the welding load is 0.01 Ω and the internal temperature is 40°C.

[0045] Also, under another condition, it is assumed that the first detection value (primary side current) of first detection component 11 is 100 A, the second detection value (secondary side current) of second detection component 21 is 390 A, the detection value (secondary side voltage) of voltage sensor 41 is 39 V, and the detection value (internal temperature) of temperature sensor 42 is 25°C. In this case, as shown in FIG. 3 , ratio calculation unit 221 calculates 3.9 (=390 A ÷ 100 A) as the initial ratio Kzz(0.1,25) when the resistance value of the welding load is 0.1 Ω (=39 V ÷ 390 A) and the internal temperature is 25°C, and stores this in memory unit 222. That is, the value 3.9 is stored in memory unit 222 as the initial ratio Kzz(0.1,25) under the condition that the resistance of the welding load is 0.1 Ω and the internal temperature is 25°C, as shown in FIG. 3 .

[0046] Also, under another condition, it is assumed that the first detection value (primary side current) of first detection component 11 is 100 A, the second detection value (secondary side current) of second detection component 21 is 400 A, the detection value (secondary side voltage) of voltage sensor 41 is 4 V, and the detection value (internal temperature) of temperature sensor 42 is 25°C. In this case, as shown in FIG. 3 , ratio calculation unit 221 calculates 4 (=400 A ÷ 100 A) as the initial ratio Kzz(0.01, 25) when the resistance value of the welding load is 0.01 Ω (=4 V ÷ 400 A) and the internal temperature is 25°C, and stores this in memory unit 222. That is, the value 4 is stored in memory unit 222 as the initial ratio Kzz(0.01, 25) under the condition that the resistance of the welding load is 0.01 Ω and the internal temperature is 25°C, as shown in FIG. 3 .

[0047] The correction value calculation unit 223 of the welding device A2 calculates a correction value for the secondary-side current detection signal of the second detection component 21 using the initial ratio Kzz corresponding to the current conditions (resistance value and internal temperature of the welding load). If the specific conditions (resistance value and internal temperature of the welding load) for each initial ratio Kzz match, the correction value calculation unit 223 calculates the correction value using the value of the initial ratio Kzz under those conditions. If the specific conditions do not match, the correction value may be calculated using the value of the initial ratio Kzz under the closest conditions, or the previously calculated correction value may be used. Then, like the output unit 224 of the welding device A1, the output unit 224 of the welding device A2 corrects the secondary-side current detection signal of the second detection component 21 using the correction signal input from the correction value calculation unit 223 and outputs the corrected secondary-side current detection signal to the control unit 3.

[0048] In welding device A2, similar to welding device A1, correction unit 22 corrects the detection signal (secondary-side current detection signal) of second detection component 21 so that the ratio of the second detection value of second detection component 21 to the first detection value of first detection component 11 is constant. Therefore, similar to welding device A1, welding device A2 corrects the second detection value of second detection component 21 according to the first detection value of first detection component 11. Therefore, even if second detection component 21 deteriorates over time, the corrected secondary-side current detection signal of second detection component 21 can be used, enabling appropriate feedback control of the welding output. In addition, welding device A2 achieves the same effects as welding device A1 by using a configuration common to welding device A1.

[0049] Furthermore, in the welding device A2, the initial ratio includes multiple values ​​depending on predetermined conditions. This configuration allows the initial ratio to be changed according to predetermined conditions. For example, when performing consumable electrode welding, the welding load repeatedly arcs and shorts, which can cause the resistance value of the welding load to fluctuate. Therefore, correction unit 22 of welding device A2 stores initial ratios corresponding to the resistance value of the welding load in memory unit 222, and correction value calculation unit 223 of correction unit 22 calculates a correction value using the initial ratio corresponding to the current resistance value of the welding load. This allows the initial ratio value to be changed according to fluctuations in the resistance value of the welding load, allowing correction unit 22 to calculate an appropriate correction value. Furthermore, the power conversion efficiency of components of the conversion unit (e.g., the transformer of transformer INT and the diode of rectifying and smoothing circuit DR2) can fluctuate depending on the internal temperature of the welding device A2 due to their temperature characteristics. Therefore, correction unit 22 of welding device A2 stores in memory unit 222 initial ratios corresponding to the internal temperatures of welding device A2, and correction value calculation unit 223 of correction unit 22 calculates a correction value using the initial ratio corresponding to the current internal temperature of welding device A2. This allows the value of the initial ratio to be changed in accordance with fluctuations in the internal temperature of welding device A2, so that correction unit 22 can calculate an appropriate correction value.

[0050] In the second embodiment, the predetermined conditions include the resistance value of the welding load and the internal temperature of the welding device A2. In an example different from this configuration, the predetermined conditions may include only one of the resistance value of the welding load and the internal temperature of the welding device A2. However, in order to improve the correction accuracy of the secondary side current detection signal of second detection component 21, it is preferable that the predetermined conditions include both of these. Furthermore, the predetermined conditions may include conditions other than the resistance value of the welding load and the internal temperature of the welding device A2.

[0051] 4 shows a welding device A3 according to a third embodiment. The welding device A3 differs from the welding device A1 in that the output side detector 2 includes an offset adjuster .

[0052] The offset adjustment unit 23 performs offset adjustment of the second detection component 21. Even when no current flows through the line 93 (even when the line 93 is in a non-energized state), an offset voltage may be generated. The offset voltage is superimposed on the current detection signal (secondary-side current detection signal) of the second detection component 21, resulting in an offset error in addition to an output amplification error. Therefore, the offset adjustment unit 23 calculates a second detection value of the second detection component 21 when the secondary-side current is 0 A, i.e., when the output of the inverter circuit INV is 0 A. Then, the offset adjustment unit 23 calculates an offset value that makes the second detection value 0. The offset adjustment unit 23 receives the secondary-side current detection signal from the second detection component 21, adds the calculated offset value to the secondary-side current detection signal, and outputs the offset-adjusted secondary-side current detection signal to the correction unit 22 (ratio calculation unit 221, correction value calculation unit 223, and output unit 224). Thereafter, the correction unit 22 corrects the secondary-side current detection signal, similar to the welding device A1.

[0053] In welding device A3, similar to welding device A1, correction unit 22 corrects the detection signal (secondary-side current detection signal) of second detection component 21 so that the ratio of the second detection value of second detection component 21 to the first detection value of first detection component 11 is constant. Therefore, similar to welding device A1, welding device A3 corrects the second detection value of second detection component 21 according to the first detection value of first detection component 11, so that even if second detection component 21 deteriorates over time, the corrected secondary-side current detection signal of second detection component 21 can be used, enabling appropriate feedback control of the welding output. In addition, welding device A3 achieves the same effects as welding device A1 by using a configuration common to welding device A1.

[0054] Furthermore, in welding device A3, correction unit 22 of output side detection unit 2 corrects the offset-adjusted secondary side current detection signal so that the ratio is constant, as in welding device A1, and outputs the corrected signal to control unit 3. Therefore, in welding device A3, control unit 3 controls inverter circuit INV using the secondary side current detection signal in which both the offset error and the gain error have been corrected, thereby enabling more appropriate feedback control.

[0055] In the third embodiment, an example in which the offset adjuster 23 is provided in the welding device A1 has been described, but the offset adjuster 23 may also be provided in the welding device A2. Furthermore, in the third embodiment, an example in which the offset adjuster 23 is provided in the output side detector 2 has been described, but in addition, an offset adjuster equivalent to the offset adjuster 23 may also be provided in the input side detector 1.

[0056] In the first to third embodiments, when correcting the second detection value (secondary-side current detection signal) with a correction value (correction signal), the output unit 224 may use an average value of several past correction values ​​(e.g., the past 10 or 100) as the correction value. For example, the correction value calculation unit 223 stores the correction value in the storage unit 222 every time it calculates it. As a result, previously calculated correction values ​​are stored in the storage unit 222, and the output unit 224 calculates an average value of several past correction values ​​(e.g., the past 10 or 100) stored in the storage unit 222. Then, the output unit 224 corrects the secondary-side current detection signal using the calculated average value of the correction values. Note that the calculation of the average correction value may be performed by the correction value calculation unit 223. If noise or the like is applied to at least one of the primary-side current detection signal and the secondary-side current detection signal, the correction value calculated by the correction value calculation unit 223 may be an abnormal value. Therefore, by using the average value of the past several correction values ​​in the configuration according to this modification, it is possible to suppress the occurrence of sudden abnormal values.

[0057] In the first to third embodiments, an example was shown in which the first detection component 11 is a CT (instrument current transformer). However, instead of this configuration, the first detection component 11 may be a shunt resistor. In this case, the ratio calculation unit 221 and the correction value calculation unit 223 of the correction unit 22 may convert the inter-terminal voltage of the shunt resistor into a current value (input current) corresponding to the inter-terminal voltage, and calculate the ratio and correction value, respectively. Alternatively, the input-side detection unit 1 may convert the inter-terminal voltage of the shunt resistor into a current value corresponding to the inter-terminal voltage, and output the converted primary-side current detection signal to the output-side detection unit 2.

[0058] In the first to third embodiments, the output-side detector 2 may be provided with a fault detection unit that detects a fault in the second detection component 21. For example, the fault detection unit determines that the second detection component 21 is faulty when the ratio calculated by the ratio calculation unit 221 deviates by a predetermined value or more. In this example, the fault detection unit determines that the second detection component 21 is faulty when the ratio is 1.2 times or more the transformation ratio of the transformer INT. Alternatively, for example, the fault detection unit determines that the second detection component 21 is faulty when the correction value calculated by the correction value calculation unit 223 deviates by a predetermined value or more. In this example, in a configuration in which the maximum rated output of the welding current is 300 A or more and 600 A or less, the fault detection unit determines that the second detection component 21 is faulty when the correction value is 50 A or more. Alternatively, when no current is being output (when the inverter circuit INV is stopped and no current is flowing through the line 93), the fault detection unit determines that an abnormality has occurred when the output value of the second detection component 21 exceeds ±30 A. Note that these numerical examples are merely examples and are not limiting. If second detection component 21 is faulty, the fault detection unit described above may notify the fault by a notifying means (not shown).

[0059] In the above first to third embodiments, an example has been shown in which the correction unit 22 is provided in the output-side detection unit 2. However, instead of this configuration, the correction unit 22 may be provided in the control unit 3. In this case, the secondary-side current detection signal of the second detection component 21 is output to the control unit 3, and the correction unit 22 in the control unit 3 corrects the secondary-side current detection signal.

[0060] The welding device according to the present disclosure is not limited to the above-described embodiment, and the specific configuration of each part of the welding device according to the present disclosure can be freely modified in various ways. [Explanation of symbols]

[0061] A1, A2, A3: welding equipment, DR1, DR2: rectifying and smoothing circuit, INT: transformer, INV: inverter circuit, 11: first detection component, 21: second detection component, 22: correction unit, 221: ratio calculation unit, 222: memory unit, 223: correction value calculation unit, 224: output unit, 3: control unit, 41: voltage sensor, 42: temperature sensor

Claims

1. 1. A welding device for supplying current to a welding load, comprising: a conversion unit that converts an input current and outputs the converted current; a first detection component for detecting an input current to the conversion unit; a second detection component for detecting an output current of the conversion unit; a correction unit that corrects the detection signal of the second detection component and outputs the corrected detection signal; Equipped with The correction unit corrects the detection signal of the second detection component so that a ratio of a second detection value of the second detection component to a first detection value of the first detection component is constant.

2. 2. The welding device according to claim 1, wherein the correction unit includes: a ratio calculation unit that calculates an initial ratio, which is the ratio at a first time point before the present time; a correction value calculation unit that calculates a correction value for correcting the detection signal of the second detection component using the initial ratio; and an output unit that corrects the detection signal of the second detection component with the correction value and outputs the detection signal.

3. The initial ratio includes a plurality of values ​​depending on the state of the welding load, The welding device according to claim 2 , wherein the correction value calculation unit changes the value of the initial ratio to be used depending on the state of the welding load.

4. the initial ratio includes a plurality of values ​​depending on the internal temperature of the welding device; 4. The welding device according to claim 2, wherein the correction value calculation unit changes the value of the initial ratio to be used depending on the internal temperature.

5. the correction unit includes a storage unit that stores the correction value calculated by the correction value calculation unit, The welding device according to claim 2 , wherein the output unit corrects the detection signal of the second detection component using an average value of the plurality of correction values ​​stored in the storage unit.

6. an inverter circuit that inputs a current to the conversion unit; 3. The welding device according to claim 1, further comprising: a control unit that receives the corrected detection signal from the correction unit and controls the inverter circuit using the corrected detection signal.

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