Method for limiting the welding power of a welding device - Patents.com

Abstract

To ensure a stable welding process, a supply power P1 is supplied to the welding device 1 by a power source 2, and at least a portion of the supply power P1 is converted into a welding power P2 to generate a welding arc arc. In this case, the welding power P2 is controlled by presetting a welding current I2. For this purpose, a supply voltage U1 is calculated, and a maximum supply current I that can be output from the power source 2 to the welding device 1 is calculated. 1,max The supply voltage U1 and the maximum supply current I 1,max The maximum supply voltage U1 is calculated using the maximum welding power P output from the welding device 1. 2,max is the maximum supply current I 1,max The welding power P2 is calculated from the maximum welding power P that can be output. 2,max is limited to.

Description

[Technical Field]

[0001] The present invention relates to a method for operating a welding device, wherein a supply power is supplied to the welding device by a power source and at least a portion of the supply power is converted into a welding power for generating a welding arc, wherein the welding power is controlled by a predetermined welding current, and wherein a supply voltage is calculated. Furthermore, the present invention relates to a welding device for generating a welding arc by converting a supply power into a welding power, wherein the welding device is configured to control the welding power by a predetermined welding current. [Background technology]

[0002] The welding device generates a welding voltage and a welding current at the electrode during the welding process, i.e., during ignition and generation of the welding arc. The welding device then outputs an arc power calculated from the welding voltage and the welding current via the welding arc. Supply power is supplied to the welding device from a power source. For example, a power grid or a generator may serve as the power source. Naturally, a voltage converter (inverter, rectifier, converter, etc.) may be provided between the power source and the welding device for the power supply to power the welding device. The conversion of the supply power to the welding power is performed by a power supply unit. In this case, the welding device controls the welding power by presetting the welding current. For example, the welding current may be controlled to a preset target value. The welding voltage may be adjusted manually, for example, depending on the length of the welding arc.

[0003] Methods for limiting the output welding power are known. DE 35 23 879 A1 discloses a method for limiting the welding power to avoid spatter during welding. This method is carried out by measuring the welding current and welding voltage and limiting the welding power to preset limit values.

[0004] A welding power supply with a dynamic power limiting function is known from US Patent Application Publication No. 2018 / 0056428. For this purpose, static and dynamic parameters of the power supply, such as information about the maximum power loss, the maximum available power, the temperature or power drop, the actual input / output voltage values, the actual input / output current values, etc., are provided to one control module of the power supply from another module of the power supply. Then, based on the static and dynamic parameters, the maximum output power or power loss and the maximum allowable output power or power loss are calculated as dynamic determining factors, and based on the parameters, the output parameters (i.e., output voltage, output current and / or output power) are adapted by the control module.

[0005] Furthermore, a welding system and a corresponding method are known from US Patent Application Publication No. 2009 / 0277893, in which output power characteristics are calculated based on inputtable configuration parameters (e.g., wire diameter, material thickness, etc.), the actual input voltage or input power is monitored and compared with an ideal input voltage or input power, e.g., without fluctuations, etc., and if the actual input power deviates from the ideal input power, the output power is adapted according to the calculated output power characteristics. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] DE 3523879 [Patent Document 2] US Patent Application Publication No. 2018 / 0056428 [Patent Document 3] US Patent Application Publication No. 2009 / 0277893 Summary of the Invention [Problem to be solved by the invention]

[0007] SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and a welding device which allow a stable welding process. [Means for solving the problem]

[0008] According to the present invention, this problem is solved by setting in advance the maximum supply current that can be output from the power source to the welding device. electric power is calculated using the supply voltage and the maximum supply current, and the maximum welding power output from the welding device is calculated by electric power and the welding power is limited to the maximum welding power that can be output.

[0009] Furthermore, this problem is solved by a welding device that includes a calculation unit configured to calculate a maximum supply power from the supply voltage of the welding device and a maximum supply current that can be output from a power source to the welding device, and to calculate a maximum welding power output from the welding device from the maximum supply power, and a limiting unit configured to limit the output welding power to the maximum welding power that can be output. Therefore, the maximum welding power that can be output is taken into account when controlling the welding power.

[0010] Therefore, the welding power is not limited based on a previously known limit value, but is also limited based on the actual maximum supply power that can be obtained using the actual supply power. From the actual maximum supply power, the actual maximum welding power can be calculated. The welding power to be output is limited based on this calculation. This prevents the welding device from attempting to control a welding power that cannot be output at all. This prevents an undesired stop of the welding process due to an undesired extinguishing of the welding arc. Fluctuations in the supply voltage can occur, in particular, due to long cables between the power source and the welding device or when a generator is used as the power source.

[0011] Advantageously, a measuring unit is provided that is configured to measure the supply voltage, so that it can be ensured that the supply voltage is actually known. Naturally, it is also conceivable that the supply voltage is pre-set in other ways, for example, that the welding device is connected to a power supply having a different supply voltage.

[0012] Preferably, the welding power is limited by limiting the welding current. To this end, the limiting unit may be configured to limit the welding current to limit the output welding power to the maximum possible supply power. If there is a current control device for controlling the welding power via the welding current, the limiting is performed by limiting the target value (i.e., target current) and / or control variable of the current control device. When the control variable is limited, it is advantageous to implement an anti-windup means to prevent the current control device from trying to control the limited control variable. Anti-windup means are basically known, so a detailed description thereof will not be given.

[0013] It is advantageous that the maximum supply current that can be output from the power source to the welding device or that can be received by the welding device is preset, particularly by a user or by automatic recognition, and the maximum supply power is calculated from the supply voltage and the maximum supply current. The maximum supply current may correspond to the cut-off current of an overcurrent protection. Unlike the supply voltage, which is considered variable, the maximum supply current is preset as a constant. In this case, the supply current is considered not to exceed the maximum supply current.

[0014] In particular, the maximum supply power output from the welding device is calculated from the maximum supply power that can be output from the power source to the welding device, taking into account the operating power. In this case, the supply power is not only used to output the welding power, but also to supply the operating power for operating the welding device. Therefore, the maximum supply power is limited by the supply power excluding the operating power. This means that the maximum welding This means that the power is equal to the maximum power supply minus the operating power.

[0015] The limiting unit can be configured to be active and inactive. Thus, for example, the user can decide whether the welding power should be limited when the amount of power changes, or whether such intervention is undesirable. In particular, if the change in the supply voltage is predictable, it may be beneficial to deactivate the control unit.

[0016] The invention will now be described in more detail with reference to Figures 1 to 6c, which show exemplary, schematic and non-limiting preferred embodiments of the invention. [Brief explanation of the drawings]

[0017] [Figure 1] 1 shows a schematic representation of a welding device; [Figure 2] 1 shows a schematic representation of a welding device having a welding power supply unit. [Figure 3] 1 shows a welding device having a computing device and a limiting device. [Figure 4a] The time course of the supply voltage and the time course of the supply current are shown. [Figure 4b] The graph shows the change in welding power over time. [Figure 4c] 1 shows the transition of welding voltage and the transition of welding current over time. [Figure 5a] 10 shows detailed time transitions of the supply voltage and supply current when the supply voltage drops. [Figure 5b] 10 shows a detailed time transition of welding power when the supply voltage drops. [Figure 5c] 10 shows detailed time transitions of welding pressure and welding current when the supply voltage is reduced. [Figure 6a] 10 shows detailed time transitions of supply voltage and supply current during the limiting process of the present invention. [Figure 6b] 10 shows detailed time transitions of welding power when limited by the present invention. [Figure 6c] 10 shows detailed time transitions of welding pressure and welding current when limited by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] 1 shows a schematic diagram of a welding device 1 receiving a supply power P1 from a power source 2. In this case, the power source 2 supplies a supply voltage U1 and a supply current I1 to the welding device 1. The supply power P1 can be expressed as the product of the supply voltage U1 and the supply current I1: P1 = U1 · I1.

[0019] The welding device 1 generates a welding arc at the electrode by outputting a welding power P2 during the welding process. The welding power P2 can be expressed as the product of the welding current I2 and the welding voltage U2: P2 = U2 · I2. Therefore, the welding current I2 passing through the electrode is generated by the welding device 1 during the welding process, i.e., when the welding arc is generated, while the welding voltage U2 is generated at the electrode. The welding voltage U2 is known, for example, by measurement.

[0020] A welding control unit 10 is provided to control the welding power P2. In the illustrated figure, a current control device that controls the welding current I2 is also provided as the welding control unit 10 to control the welding power P2. To control the welding power P2, the welding control unit 10 is configured to preset a target variable, for example, by a user. In the illustrated current control device, a target current I2 is set to control the welding power P2. 2,soll is preset. A welding voltage U2 is generated during the output of the welding current I2. The welding voltage U2 can be controlled, for example, by adjusting the length of the welding arc, for example, by changing the distance from the welding torch to the workpiece. This means that the welding power P2 is controlled by the preset target current I 2,soll on the one hand, by the welding power P2 controlled in response to, and on the other hand, by the welding voltage U2 preset.

[0021] 2, the welding device 1 may include a voltage converter 14, i.e., an AC / DC converter or a DC / DC converter, and a welding power supply unit 13 connected to the voltage converter 14. In this case, the voltage converter 14 generates a buffer circuit voltage U1 that inputs the supply voltage U1 to a capacitive buffer circuit Z. ZAs a result, the supply power P1 is buffer-charged in the buffer circuit Z. The welding power supply unit 13 is powered by the buffer circuit Z and outputs the welding current I2, i.e., the welding power P2, in response to a request from the welding control unit 10 during the welding process. Various possible basic configurations of the welding device 1 are known, and therefore will not be described in detail.

[0022] Figure 3 shows the entire welding device 1 according to Figure 1, which is used to explain the invention. Naturally, the invention can also be used with a welding device 1 according to Figure 2 or with another type of welding device 1.

[0023] According to the present invention, the maximum supply power P that can be output from the power source 2 to the welding device 1 is 1,max Preferably, a calculation unit 12 is provided which is configured to calculate the maximum supply power P 1,max is the supply voltage U1 that is considered constant at that time and the maximum supply current that can be output from power supply 1. I 1,max It is calculated from the product of :P 1,max =U1·I 1,max The supply voltage U1 is detected in particular by a measuring unit 13.

[0024] Maximum supply current I 1,max may be preset by the cut-off current of the overcurrent protection, and may be set or preset in the welding device 1 manually by the user, for example, or may be set or preset by an automatic recognition method of the power source 2.

[0025] Basically, the maximum welding power P that can be output from the welding device 1 2,max is the maximum power supply P received by the welding device 1 (i.e., output from the power source 2). 1,max However, in order to operate the welding device 1, for example, the operating power P required for buffer charging the buffer power in the buffer circuit Z is b Similarly, the operating power P b If the maximum welding power P is also received from the supply power P1, 2,max When calculating the power supply P1, bis subtracted from the power supply: P 2,max =P 1,max -P b .

[0026] Operating power P b Also, the supply voltage U1 and the operating current I b This can be expressed as the product of the maximum welding power P 2,max is P 2,max =U1(I 1,max -I b ) can be written as

[0027] The welding control device 10 determines the maximum welding power P in relation to the generated welding voltage U2. 2,max A situation may occur in which the welding current I2 is controlled to cause the welding power P2 to exceed the maximum outputtable welding power P 2,max is decreasing, for example due to a reduced supply voltage U1, or when the welding voltage U2 is increasing.

[0028] The actual welding power P2 is the maximum welding power P 2,max The product of the welding current I2 and the welding voltage U2 is the actual welding power P 2,max Similarly, the welding current I2 is set to a predetermined target value I 2,soll Therefore, if the welding power P2 is not limited, the supply current I1 (and the corresponding cut-off current of the overcurrent protection) will increase too much and / or the limit supply voltage U (the welding process will be impossible) will be exceeded. 1,min Therefore, according to the invention, the welding power P2 is limited by the limiting part 11 to the maximum welding power P2. 2,max is limited to.

[0029] In particular, the limitation is performed by limiting the welding current I2. As shown in FIG. 3, the limitation is performed by limiting the target value I of the welding current I2, which is also controlled. 2,sollHowever, the control variable of the welding control device 10 may also be limited. By limiting the welding current I2, it can be ensured that the welding voltage U2 can be maintained when the welding power P2 is reduced.

[0030] The following is an example of limiting the welding current I2 (i.e., the controlled variable): A differential welding power ΔP2 is calculated at the actual time. This differential welding power ΔP2 is calculated based on the maximum welding power P 2,max and the welding power P2 to be output: ΔP2 = P 2,max -P2.

[0031] Actual control step P of welding power 2,i To limit the welding power per 2,i may be filtered and used (P 2,i =Filtering(P 2,max -P b )), or may be used unfiltered.

[0032] Therefore, the power loss P loss If is further considered, the welding power is 2,i =P 2,max -P b -P loss or P 2,i =Filtering(P 2,max -P b -P loss ) is obtained for the power loss P loss represents in particular the switching and conduction losses in semiconductor switches (transistors) and the ohmic losses in, for example, cables, transformers, etc. In contrast, the operating power P b includes the power buffered and charged in the buffer circuit Z.

[0033] Furthermore, the actual welding current I 2,i However, the actual welding power P 2,i and the actual welding voltage generated

[0034]

number

[0035] Correspondingly, the course of the supply voltage U1, the course of the welding current I2 and the course of the welding voltage U2 are shown in FIGS. 4a, 4b and 4c.

[0036] 4a shows the time course of the supply voltage U1 and the time course of the supply current I1. In FIG. 4a, the supply current I1 is constant throughout. The supply voltage U1 is at a first voltage value up to a first time point t1, and decreases from the first time point t1 to a second time point t2. 10 The supply voltage U1 decreases from the constant first voltage value to the constant supply voltage U2, and then increases to the initial first voltage value after the second time point t2. 10 The stepwise change to the first voltage value and the subsequent stepwise increase to the constant first voltage value are shown solely for the sake of easier explanation and are therefore merely exemplary. A drop in the supply voltage U1 can occur, for example, due to an overload, a fault, etc. of the power source 2 and / or the cable from the power source 2 to the welding device 1. In this case, the supply current I1 is constant, so that the profile P1 of the supply power (not explicitly shown) coincides with the profile of the supply voltage U1.

[0037] 4b shows the course of the welding power P2 when the present invention is used, and FIG. 4c shows the course of the welding current I2 when the present invention is used. The welding current I2 is maintained at the same target current I2 up to the time t1. 12,soll The welding power P2 is obtained as the product of the welding current I2 and the welding voltage U2. After the first time point t1, the supply voltage U1 is controlled to the reduced supply voltage U2 as described above. 10 Therefore, after the first time point t1, the maximum supply power P 1,max The maximum supply current I 1,max is set to a constant value in advance.

[0038] Therefore, from the first time point t1 onwards, the maximum supply power P 1,max The welding power P2 obtained from the reduced maximum welding power P 2,max The welding current I2 is reduced to the target current I1, which remains unchanged (without limitation) from the first time point onwards. 2,soll If the supply current I1 must be controlled to a value lower than the reference voltage, the supply current I1 is increased as described below with respect to FIGS. 5a, b, c.

[0039] Therefore, the welding current I2 is preferably limited from the first time point t1 onwards (FIG. 4c). 2,soll Alternatively, the limited welding power P2 can be implemented by intervening in a control variable. The limited welding power P2 is obtained from a preset (for example, constant) welding voltage U2 between a first time t1 and a second time t2 and a controlled (here, limited) welding current I2. The rise time, time delay, and upper and lower limits of the welding power P2 in Fig. 4b and the rise time, time delay, and upper and lower limits of the welding current in Fig. 4c are exaggerated and are used only for a better understanding of the invention.

[0040] Naturally, the limitation of the welding power P2 is not performed instantaneously, as can be seen in Figures 4a, b, and c, because the welding control device 10 must first respond to the new target or control value. It is essentially advantageous that the limitation of the welding current I2 is not performed in a stepped manner, because this would cause a very clearly audible noise.

[0041] 5a, 5b, and 5c show detailed progressions of the supply parameter, i.e., supply voltage U1, and the welding parameters, i.e., welding voltage U2 and welding current I2, relative to time t1 of FIGS. 4a, 4b, and 4c when the control / limitation of the present invention is not implemented or is not performed. Accordingly, the first time point t1 shown in FIGS. 4a, 4b, and 4c is now shown in detail as individual finer time points t3, t4, and t5. The duration of these finer time points t3 to t5 may be, for example, 5 milliseconds to 5 seconds. In this case, the duration of the finer time points t3 to t5 is preferably 200 milliseconds.

[0042] 5a, the supply voltage U1 drops, for example, at a small instant t3, due to an extreme effect (fluctuations in the power grid). In this case, the value of the supply voltage U1 falls below the limit supply voltage U1 by a small instant t4. 1,min The limit supply voltage U (which may vary depending on the power supply 2) is reached. 1,min The power supply 2 can still supply a constant welding current I2 until the limit supply voltage U 1,min When the limit supply voltage U 1,min ), the welding device 1 is stopped. Therefore, the supply current I1 drops to a value of 0 A (FIG. 5a). After the supply current I1 drops to 0 A, the supply voltage U1 rises to a value smaller than the supply voltage U1 for the time instant t3.

[0043] Since the welding device 1 stops at time t4, the welding current I2 and the welding voltage U2 are not generated (FIG. 5c). As a result, the welding arc is extinguished. Since the supply current I1 drops to 0 A at time t4, the supply power P1 also drops to 0 W at time t4, as can also be seen in FIG. 5b.

[0044] 6a, 6b, and 6c show the detailed progression of the supply and welding parameters relative to time t1, similarly to FIGS. 5a, 5b, and 5c. In this case, precise times t3, t4, and t5 are shown. Unlike FIGS. 5a, 5b, and 5c, in FIGS. 6a, 6b, and 6c, the limitations of the present invention are applied. In this case, for easier representation, instantaneous ideal control is adopted. Therefore, here, when the supply voltage U1 decreases, the welding current I2 is immediately reduced. As a result, unlike in FIGS. 4b and 4c, there is no time delay, rise time, or overshoot or undershoot of the welding power P2 and the welding current I2. Therefore, here too, the supply voltage U1 decreases, for example, due to an extreme effect, after the precise time t3 (FIG. 6a). However, since the welding current I2 is reduced due to the limitations of the present invention, the supply current I1 can be maintained constant. This allows the supply voltage U1 to be reduced to the limit supply voltage U2. 1,min , the welding arc is maintained. Thus, according to the present invention, a very rapid drop in the supply voltage U1 can be avoided by reducing the welding current I2. 1,min The supply voltage U1 does not reach or fall below the supply voltage U2 at the time t5, and the welding device 1 does not stop. 10 This supply voltage U 10 is maintained at 100% (see Figure 4a).

[0045] The course of the supplied power P1 corresponds to the course of the supply voltage U1 due to the constant supply current I1 (caused by the limitation of the welding power P2). In Fig. 6b, the available supply power P1 and the welding power P2 are shown. The interval between the supplied power P1 and the welding power P2 is the power loss P of the welding system. loss Shows.

[0046] The calculation unit 12 and / or the limiting unit 11 may comprise microprocessor-based hardware, e.g., a computer or digital signal processor (DSP) on which corresponding software for performing the respective functions is executed. The calculation unit 12 and / or the limiting unit 11 may comprise an integrated circuit, e.g., an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA), or a complex programmable logic device (CPLD), and / or may be monitored by a microprocessor in parallel with the calculation unit 12 and / or the limiting unit 11. However, the calculation unit 12 and / or the limiting unit 11 may also comprise analog circuits or an analog computer. Hybrid solutions are also conceivable. Various functions can be implemented on the same and / or different hardware components. A hybrid solution, in which individual units are implemented by both hardware and software, is particularly advantageous. [Explanation of symbols]

[0047] 1. Welding equipment 2 power supply 10 Welding control unit 11 Restrictions 12 Arithmetic section 13 Welding power supply unit, measurement unit 14 Voltage conversion device P1 supply power U1 supply voltage U2 welding voltage I1 supply current P2 welding power Z-buffer circuit U Z Buffer Circuit Voltage arc welding arc I 2,soll target current P 1,max Maximum power supply I 1,max Maximum supply current P 2,max Maximum Welding Power P b Operating Power U 1,minSupply Voltage Limit

Claims

1. A method for operating a welding device (1), comprising: Supply power (P １ ) is supplied to the welding device (1) by a power source (2), and the supply power (P １ At least a part of the welding power (P ２ ) and The welding power (P ２ ) is the welding current (I ２ ) is preset, Supply voltage (U １ ) is detected, The maximum supply current (I １，ｍａｘ ) is preset, The maximum supply power (P 1,max) is the supply voltage (U １ ) and the maximum supply current (I １，ｍａｘ ) and The maximum welding power (P ２，ｍａｘ ) is the maximum supply power (P １，ｍａｘ ) is calculated from The welding power (P ２ ) is the maximum welding power (P ２，ｍａｘ )

2. The welding power (P ２ ) is the welding current (I ２ 2. The method of claim 1, wherein the limit is set by limiting

3. The maximum welding power (P ２，ｍａｘ ) is the operating power (P ｂ ) is taken into consideration, the maximum supply power (P １，ｍａｘ 3. The method according to claim 1, wherein the calculated value is calculated from the above formula (1).

4. Supply power (P １ ) to the welding power (P ２ ) to generate a welding arc, the welding apparatus (1) comprising: ２ ) to a preset welding current (I ２ In the welding device (1), The supply voltage (U １ ) and the maximum supply current (I １，ｍａｘ ) and the maximum supply power (P １，ｍａｘ ) and calculate the maximum supply power (P １，ｍａｘ ) to obtain the maximum welding power (P ２，ｍａｘ a calculation unit (12) configured to calculate Output welding power (P ２ ) is the maximum welding power that can be output (P ２，ｍａｘ The welding device (1) is provided with a restriction portion (11) configured to restrict the welding force to a predetermined value.

5. 5. The welding device (1) according to claim 4, characterized in that it is provided with a measuring part (13) arranged to measure the supply voltage (U1).

6. Output welding power (P ２ ) is the maximum welding power that can be output (P ２，ｍａｘ 6. The welding device (1) according to claim 4 or 5, characterized in that the limiting part (11) is configured to limit the welding current (I2) to a value equal to or less than 1000 .mu.m.

7. The welding device (1) according to any one of claims 4 to 6, wherein the limiting portion (11) is configured to be operable and stoppable.

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