Welding current source for an orbital welding device, having a coil with an intermediate tap

Abstract

The invention relates to a welding current source (128) for an orbital welding device (100, 101), having a first and a second output (174, 176) for feeding an arc welding process of an orbital welding device (100, 101). The welding current source (128) has a coil (604) which has a first coil connection (606), a second coil connection (610), and an intermediate tap (608), a first winding part (612) of the coil (604) being electrically connected between the first coil connection (606) and the intermediate tap (608) and a second winding part (614) of the coil (604) being electrically connected between the intermediate tap (608) and the second coil connection (610). The invention further relates to a method for operating the welding current source (128), to an orbital welding device (100, 101) having such a welding current source (128), and to a system (700) having such an orbital welding device (100, 101).

Description

[0001] Welding power source for an orbital welding device with a coil having an intermediate tap

[0002] The present invention relates to a welding power source for an orbital welding device, comprising a first and a second output for supplying an arc welding process of an orbital welding device. The present invention further relates to a method for operating the welding power source and to an orbital welding device with such a welding power source. The invention also relates to a system and an orbital welding process.

[0003] In the prior art, arc-based orbital welding processes, in particular tungsten inert gas (TIG) welding processes, are used, for example, for the metallurgical joining of pipes. In this process, the pipe ends to be joined are typically arranged side by side in a butt joint and welded together by moving the welding tool circumferentially (orbitally) around the joint. The welding torch can be guided manually or automatically.

[0004] On the outside of the pipes, discoloration can be largely suppressed by the shielding gas used in TIG welding; however, residual heat in the workpiece can still cause oxidation after the welding process. To protect the inner surface of the pipes from oxidation, additional measures are necessary, such as purging the pipes with forming gas.

[0005] Orbital welding of copper pipes has proven particularly challenging in this respect. Due to copper's high thermal conductivity, the heat introduced into the material from the outside during the welding process is quickly dissipated, requiring higher energy levels to reach the necessary temperatures at the weld point. This results in increased energy consumption, making the use of battery-powered welding equipment difficult. Furthermore, copper's high thermal conductivity leads to significant heating of the pipe's inner surface, making it particularly susceptible to discoloration and oxidation.

[0006] Furthermore, the use of battery-powered welding equipment, especially handheld devices, is made more difficult by the fact that the welding power sources commonly used in the prior art require rather expensive and / or large electronic components, for example rather expensive and large coupling transformers, which are poorly suited for a handheld device.

[0007] Against this background, the present invention is based on the objective of providing a welding power source, a method for operating it, an orbital welding device with such a welding power source, a system with such an orbital welding device and an orbital welding method, with which at least some of the aforementioned problems can be reduced or avoided.

[0008] The aforementioned problem is solved according to the invention by a welding power source for an orbital welding device, with a first and second output for supplying an arc welding process of an orbital welding device, wherein the welding power source has a coil which has a first coil connection, a second coil connection and an intermediate tap, wherein a first winding part of the coil is electrically connected between the first coil connection and the intermediate tap and a second winding part of the coil is electrically connected between the intermediate tap and the second coil connection.

[0009] It has been found that the use of such a coil with an intermediate tap for a welding power source makes it possible to provide the ignition voltages necessary for an orbital welding process, especially for contactless ignition, and regulated welding currents, and to manufacture the welding power source in a more compact and / or cost-effective manner than conventional welding power sources, for example welding power sources with a coupling transformer.

[0010] The welding power source described above, or an embodiment thereof, can be used in particular for the orbital welding device described below, or an embodiment thereof.

[0011] Preferably, the welding power source has a power supply with two terminals, in particular a first and a second terminal, and an electronically controlled intermediate tap switch. The welding power source is further preferably wired such that the first winding of the coil can be switched between the terminals of the power supply via the intermediate tap and the intermediate tap switch, and that the first and second windings of the coil can be switched between the terminals of the power supply via the second coil terminal and the outputs of the welding power source.

[0012] A welding power source connected in this way enables the reliable generation of the necessary ignition voltages to ignite an arc for orbital welding.

[0013] By connecting the welding power source in such a way that the first winding of the coil can be switched between the terminals of the power supply via the intermediate tap and the intermediate tap switch, a voltage can be applied between the first coil terminal and the intermediate tap with the power supply when the intermediate tap switch is closed, so that a current flow is built up through the first winding.By further connecting the welding power source in such a way that the first and second windings of the coil can be switched between the terminals of the power supply via the second coil connection and the outputs of the welding power source, an ignition voltage generated by the power supply and the coil can be applied to the outputs of the welding power source, so that a welding arc can be ignited via an ignition gap between the two outputs of the welding power source, in particular between a welding electrode and a workpiece.

[0014] Furthermore, a welding power source connected in this way also enables a reliable welding process after the ignition of the welding arc, in that the welding current can build up directly after ignition in the arc through the same coil.

[0015] Preferably, the welding power source has a power supply with a first and a second connection, wherein the first connection of the power supply is electrically connected to the first coil connection of the coil, the first output is electrically connected to the second coil connection of the coil, the second output is electrically connected to the second connection of the power supply, and the intermediate tap is electrically connected to the second connection of the power supply via an electronically controllable intermediate tap switch.In this way, the welding power source can be easily wired so that the first winding of the coil can be switched between the power supply terminals via the intermediate tap and the intermediate tap switch, and that the first and second windings of the coil can be switched between the power supply terminals via the second coil terminal and the outputs of the welding power source. This ensures reliable arc ignition and reliable welding operation. The power supply is specifically designed to provide a voltage between the two terminals, or between the first and second terminals, during operation. This voltage can be constant and / or variable.

[0016] The power supply preferably comprises a DC voltage source or inputs for connecting a DC voltage source. The DC voltage source can be, for example, a battery. The DC voltage source is preferably replaceable. The DC voltage source can also be permanently connected to the power supply and, for example, physically integrated into it, such as in the form of a non-replaceable battery, perhaps in a common housing with the power supply. In particular, the DC voltage source can be permanently connected to the inputs of the power supply, for example, by soldering.

[0017] In the simplest case, the inputs for connecting the DC voltage source also serve as the terminals of the power supply. In this case, the power supply merely provides the interface for connecting the DC voltage source.

[0018] The power supply is preferably configured to modify the voltage provided by the DC voltage source or via the inputs, in particular DC voltage, especially to convert it into a time-dependent voltage, for example in the form of voltage pulses, and to provide the modified voltage via the terminals of the power supply. In this way, the power supply can, for example, be used to control the welding current for carrying out a welding process after the ignition of the welding arc.

[0019] The power supply may, in particular, include an electronic switching unit. The electronic switching unit is preferably configured to switch the electrical voltage between the two terminals of the power supply back and forth between at least two voltage ranges, in particular between a first voltage range and a second voltage range. For this purpose, the electronic switching unit may, in particular, include a half-bridge circuit.

[0020] The first voltage range can be, in particular, the range of voltage provided by the DC voltage source, via the inputs of the power supply, or by a DC-DC converter, especially a boost converter, supplied by the DC voltage source or the inputs of the power supply. The first voltage range can be a single voltage value or a range around a voltage value, for example, if the supplied voltage is current-dependent.

[0021] The second voltage range is preferably a lower voltage range, i.e., the one or more voltage values ​​of the second voltage range are preferably lower than the voltage values ​​of the first voltage range. The second voltage range can be a single voltage value or a range around a voltage value, for example, if the supplied voltage is current-dependent.

[0022] To switch to the second voltage range, the electronic switching unit can be configured in particular to electrically connect the two terminals of the power supply, for example via a low electrical resistance, such as the through-resistance of a FET.

[0023] The second voltage range is therefore preferably less than IV, in particular less than 0.5V. By connecting the terminals of the power supply, these are effectively short-circuited, so that the coil can be electrically connected almost directly between the outputs of the welding power source. Due to the finite contact resistance of the electronic switching unit, a small residual voltage, preferably less than IV, can also be present between the terminals in this case.

[0024] The power supply preferably has a first and a second connection. The first connection can, for example, be an output of the preferably provided electronic switching unit, in particular a half-bridge circuit, of the power supply. The second connection can be wired in the power supply such that, during operation, it is at a reference potential, for example, at the potential of a terminal of a voltage source of the power supply or of an input for connecting the voltage source.

[0025] The first terminal of the power supply is preferably electrically connected to the first coil terminal of the coil. In particular, the first terminal of the power supply is preferably connected to the first coil terminal of the coil in such a way that a voltage can be applied to the first coil terminal and a current can flow through the first winding of the coil. The first terminal of the power supply can be connected to the first coil terminal of the coil via other electronic components, for example, via a switch and / or an electrical resistor.

[0026] The power supply connections are, in particular, points in the circuit diagram of the welding power source to which another part of the welding power source's electrical circuit, such as the coil, is connected. These connections may be mechanical elements, such as sockets, forming the terminals of the power source. However, it is also conceivable that the power source connections are simply a junction point between a component of the power source and an electrical conductor for connecting another part of the welding power source's electrical circuit, or simply any point on a conductor running from a component of the power source to another part of the electrical circuit.

[0027] The first output is preferably electrically connected to the second terminal of the coil. In particular, the first output is preferably connected to the second terminal of the coil in such a way that a current flowing through the second winding of the coil can at least partially flow through the first output. The first output can be connected to the second terminal of the coil via other electronic components, for example, via a switch and / or an electrical resistor.

[0028] The second output is preferably electrically connected to the second terminal of the power supply. In particular, the second output is preferably connected to the second terminal of the power supply in such a way that a current flowing through the second output can at least partially flow through the second terminal of the power supply. The second output can be connected to the second terminal of the power supply via further electronic components, for example, via a switch and / or a resistor and / or a welding current sensor.

[0029] The intermediate tap is preferably electrically connected to the second terminal of the power supply via an electronically controlled intermediate tap switch. In particular, the intermediate tap is preferably connected to the second terminal of the power supply in such a way that a current flowing through the intermediate tap can at least partially flow through the second terminal of the power supply. Apart from the electronically controlled intermediate tap switch, the second output can also be connected to the second terminal of the power supply via other electronic components, for example, a switch, an electrical resistor, and / or a diode. A mechanical connection element, for example, a socket, can be provided at the first and second outputs for connecting further circuitry of an orbital welding device.In this way, the welding power source can, for example, be provided as a separate, preferably replaceable, unit. However, it is also conceivable that the welding power source is permanently integrated into the electrical circuit of an orbital welding device, and that the first or second output of the welding power source is formed, for example, by any point on a respective line from the welding power source to the rest of the electrical circuit of the orbital welding device.

[0030] The aforementioned problem is further solved according to the invention by a method for operating the previously described welding power source or an embodiment thereof, in which an arc ignition process is carried out, wherein during the arc ignition process a coil ignition voltage is applied between the first coil connection and the intermediate tap, so that an electric current flows through the first winding part of the coil via the first coil connection and the intermediate tap, and then the current flow via the intermediate tap is interrupted.

[0031] In this way, high ignition voltages can be achieved with the welding power source for reliable ignition of an arc between the first and second outputs of the welding power source. For this purpose, the second coil connection is electrically connected to one of the outputs of the welding power source, in particular the first output.

[0032] The current flow via the intermediate tap can be interrupted, for example, after a predetermined or configurable time period. This time period can be, in particular, the time since the coil ignition voltage was applied between the first coil connection and the intermediate tap, especially the time since the intermediate tap switch was closed. The predetermined or configurable time period can, for example, be stored in the memory of a control unit of the welding power source. The time period can be configurable insofar as it can be set—directly or indirectly—via a user interface. The time period can, for example, be in the range of 5–20 ps.

[0033] Alternatively or additionally, the current flow via the intermediate tap can be interrupted if the electric current flowing through the first winding of the coil exceeds a predetermined or predeterminable minimum current, for example 20 A.

[0034] Preferably, the welding power source has an electronically controlled intermediate tap switch by which the current flow through the intermediate tap can be interrupted. To operate such a welding power source, during the arc ignition process, preferably with the intermediate tap switch closed, a coil ignition voltage is applied between the first coil terminal and the intermediate tap. Then, for example, after a predetermined or predeterminable time period or when a minimum current through the first winding is reached, the intermediate tap switch is opened. In this way, an electric current can first be established flowing through the first coil terminal and the intermediate tap through the first winding of the coil, and the current flow through the intermediate tap can then be interrupted.

[0035] During the arc ignition process, a coil ignition voltage is applied between the first coil terminal and the intermediate tap, so that an electric current builds up, flowing through the first winding of the coil via the first coil terminal and the intermediate tap. The coil ignition voltage can be, for example, a DC voltage or a DC voltage pulse.

[0036] Applying the coil ignition voltage between the first coil terminal and the intermediate tap causes an electric current to flow through the first winding of the coil, the current increasing over time. Interrupting the current flow, particularly by opening the intermediate tap switch, after the specified time or upon reaching the minimum current, leads to a rapid change in the current in the first winding or at the intermediate tap. This results in a brief, sharp voltage spike at the intermediate tap, according to the formula Ui~Li*dI / dt, where Ui is the voltage, Li is the inductance of the first winding, and I is the current flowing through the first winding. This voltage spike at the intermediate tap causes a voltage spike at the second coil terminal, which, depending on the ratio of the number of turns in the coil windings, can be even greater than at the intermediate tap.This voltage increase can be used as an ignition voltage to ignite an arc on an ignition gap between the outputs of the welding power source. In particular, a sufficiently large voltage increase will result in a breakdown on the ignition gap.

[0037] After the current flow is interrupted by the intermediate tap and the arc is ignited between the outputs of the welding power source, a current then flows, in particular, through both windings of the coil and the ignited arc. This current flow is achieved, in particular, by the fact that the first and second windings of the coil are switchable or connected between the terminals of the power supply via the second coil terminal and the outputs of the welding power source, between which the arc burns.

[0038] The current I reached at the end of the specified time, and thus the voltage rise or ignition voltage, can be adjusted by changing the duration and / or the coil ignition voltage. Furthermore, the ignition voltage can be adjusted by changing the inductances Li of the first winding section and L2 of the second winding section.

[0039] Preferably, the welding power source comprises a control unit configured to operate the welding power source according to the previously described method for controlling it, or an embodiment thereof. For this purpose, the control unit preferably comprises at least one processor and at least one memory containing instructions, the execution of which on the at least one processor causes the operation of the welding power source according to the method. The memory can be, for example, a ROM memory or a RAM memory. For operating the welding power source, the control unit is preferably configured to control the power supply of the welding power source, in particular an electronic switching unit of the power supply, for example, to control the gates of transistors, especially FETs, of a half-bridge circuit of the electronic switching unit.The control device is preferably further configured to control the intermediate tap switch for operating the welding power source, for example to control a gate of a transistor encompassed by the intermediate tap switch, in particular FETs.

[0040] The aforementioned problem is further solved according to the invention by an orbital welding device with the welding power source described above or an embodiment thereof.

[0041] The orbital welding device comprises in particular a welding electrode and / or a holder for it as well as contacting means for contacting a workpiece, wherein the welding electrode or the holder for it is electrically connected to one of the first and second outputs of the welding power source and wherein the contacting means are electrically connected to the respective other of the first and second outputs of the welding power source.

[0042] The welding electrode is in particular a non-consumable electrode, especially a tungsten electrode, for example with or without additives. The orbital welding device is specifically designed for carrying out a TIG welding process. According to the invention, the aforementioned problem is further solved by a system comprising the previously described orbital welding device or an embodiment thereof and a fitting. The fitting is specifically designed to be used together with the orbital welding device to create a metallurgical bond between the fitting and a joining partner, in particular a pipe end, by means of orbital welding. For this purpose, the fitting is preferably adapted to the geometry of the orbital welding device.

[0043] In particular, the fitting and the welding head of the orbital welding device can have corresponding contours, such as an outer contour of the fitting and a corresponding fitting fixation contour of the welding head, in order to position the fitting in a predetermined fitting position within the welding head. The fitting position is preferably such that the joining area of ​​the fitting, for example, an edge of the fitting where the fitting is to be welded to the pipe end, is located in the area of ​​the electrode ring segment or the welding electrode, in particular with a predetermined distance, for example, of less than 1.5 mm, and more specifically less than 1.2 mm, between the tip of the welding electrode and the edge of the fitting.

[0044] The aforementioned problem is further solved according to the invention by an orbital welding process carried out with an orbital welding device, in particular with the orbital welding device described above or an embodiment thereof, in which the welding power source of the orbital welding device is operated according to the method described above for operating a welding power source or an embodiment thereof.

[0045] In particular, during the ignition process, an ignition voltage, which can be tapped via the outputs of the welding power source, is applied between the welding electrode and a workpiece, especially a fitting and / or pipe section, so that an arc ignites between the welding electrode and the workpiece. Furthermore, a welding process is preferably carried out after the ignition process. Various embodiments of the welding power source, the method for its operation, the orbital welding device, the system, and the orbital welding process are described below, with each embodiment applying independently to the welding power source, the method for its operation, the orbital welding device, the system, and the orbital welding process, respectively. Moreover, the individual embodiments can be combined with one another as desired.

[0046] In one embodiment, particularly the welding power source, the first and second windings of the coil are wound around a common core. Specifically, the first and second windings are arranged side-by-side on the core, offset axially. This allows for a particularly compact design, which is especially advantageous for handheld devices.

[0047] The coil core can be designed as a rod core, at least within the coil itself. Outside the coil, the core can be closed, with the core exiting the coil behind the second winding section and then re-entering the coil at the first winding section. This improves the guidance of the magnetic field lines outside the coil. Preferably, the coil core is closed on two opposite sides of the coil. This improves the guidance of the magnetic field lines on both sides of the coil and also achieves a symmetrical design. In particular, the coil core can be a shell-type core and / or the coil can be arranged on the coil core in a modified shell-type configuration.In contrast to a conventional shell-type arrangement, in which two separate coils are arranged one behind the other on a coil core, in the modified shell-type arrangement two winding sections of a coil with intermediate tap are arranged one behind the other on a coil core.

[0048] The coil core can, for example, be a ferrite core. In one embodiment, particularly in the welding power source, the coil core has a longitudinal gap, preferably located within the second winding section. This allows the coil assembly to store more energy for an ignition process, especially in the field within the gap.

[0049] In one embodiment, particularly the welding power source, the inductance of the second winding is greater than the inductance of the first winding. This allows for a higher ignition voltage. Preferably, the inductance of the second winding is at least twice, and more preferably at least three times, the inductance of the first winding. This allows for higher ignition voltages. This can be achieved, in particular, by having a greater number of turns in the second winding than in the first winding.

[0050] Accordingly, in one embodiment, particularly the welding power source, the ratio of the number of turns in the second winding section to the number of turns in the first winding section is greater than 1, preferably greater than 2, and particularly greater than 3. This allows for higher ignition voltages to be achieved.

[0051] In one embodiment, particularly the welding power source, the intermediate tap switch comprises a transistor, preferably a field-effect transistor, and in particular a SiC field-effect transistor. The use of a transistor, especially a field-effect transistor, allows for faster switching times and thus higher ignition voltages.

[0052] Silicon carbide (SiC)-based field-effect transistors have proven particularly suitable because they can withstand drain-source voltages of several kV, whereas silicon-based field-effect transistors, for example, can only withstand lower drain-source voltages. The higher drain-source voltages enable higher trigger voltages. While circuits that can achieve similar voltages of several kV without SiC field-effect transistors are conceivable, they are significantly more complex and larger.

[0053] In one embodiment, particularly the welding power source, one or more diodes are connected between the intermediate tap of the coil and the intermediate tap switch, especially with a reverse recovery time of less than 100 ns, preferably less than 50 ns. These one or more diodes suppress reverse current flows caused by voltage oscillations occurring during the ignition process. Diodes with a reverse recovery time of less than 100 ns, preferably less than 50 ns, are preferred because they also suppress reverse current flows for high-frequency components of the ignition voltage. The one or more diodes can be, for example, SiC diodes or Schottky diodes, which have particularly short reverse recovery times.

[0054] In one embodiment, particularly of the welding power source, a capacitor is connected between the first and second outputs. For this purpose, one or more capacitors can be connected between the first and second outputs. The capacitor connected between the first and second outputs, together with the inductance of the coil, creates a resonant circuit, allowing the oscillation frequency and voltage amplitude of the ignition voltage pulse to be adjusted. Preferably, the capacitor capacitance between the first and second outputs is matched to the total inductance of the coil such that it forms a resonant circuit with a resonant frequency in the range of 0.5–2.5 MHz, particularly 1–2 MHz. This has proven to be a preferred frequency range for the ignition process. The capacitance is preferably less than 200 pF.In one embodiment, particularly the welding power source, a welding current sensor is provided for measuring the welding current. The welding current sensor is preferably arranged at one of the outputs of the welding power source. The welding current measurements taken by the welding current sensor can be used for welding current control. The welding current sensor can be, for example, a Hall sensor or a measuring resistor.

[0055] In one embodiment, particularly of the method, a welding process with a burning arc is carried out between the first and second outputs after the ignition process. The welding process is carried out, in particular, with the intermediate tap switch open. In this way, no current flows through the intermediate tap switch, and the first and second windings of the coil are energized by the same current, so that the coil operates like a normal coil.

[0056] In one embodiment, particularly of the method, current control is performed during the welding process, especially according to a predetermined or predefinable current characteristic. For this purpose, the control device preferably acquires measured values ​​for the welding current via the welding current measuring sensor and controls the voltage supply depending on the acquired measured values ​​for the welding current.

[0057] In one embodiment, particularly of the method, the electrical voltage applied between the two terminals of the power supply is switched back and forth between at least two voltage ranges, for example two voltage values, in particular a first and a second voltage range, for example a first and a second voltage value, depending on measured values ​​for the welding current. In particular, a control device of the welding power source, in particular the control device of the power supply, can effect a corresponding regulation of the voltage supply.

[0058] As explained above, the first voltage range can be, in particular, the voltage range provided by the DC voltage source, via the inputs of the power supply, or by a DC-DC converter, especially a boost converter, supplied by the DC voltage source or the inputs of the power supply. Furthermore, the second voltage range is preferably a lower voltage range, wherein the two terminals of the power supply are preferably electrically connected when switching to the second voltage range, for example, via a low electrical resistance, such as the through-resistance of a FET. The first and second voltage ranges can each be a single voltage value or a range around a voltage value, for example, if the supplied voltage is current-dependent.

[0059] In one embodiment, particularly of the method, the electrical voltage applied between the two terminals of the power supply is switched to a first voltage range, in particular to the voltage provided by the DC voltage source or applied to the inputs of the power supply, when the measured values ​​for the welding current fall below a predetermined or predefinable lower threshold. Additionally or alternatively, the electrical voltage applied between the two terminals of the power supply is switched to a second voltage range, in particular less than 1 V, when the measured values ​​for the welding current rise above a predetermined or predefinable upper threshold. In particular, a control device of the welding power source, especially the control device of the power supply, can effect corresponding regulation of the power supply.In this way, robust welding current control can be achieved. The upper and lower threshold values ​​can be defined, in particular, by a predefined and / or predefined current characteristic curve. This allows the welding current to be regulated according to the current characteristic curve, and thus the welding arc to be operated according to the current characteristic curve.

[0060] When switching to the first voltage level, the power supply provides energy from the DC power source to the welding process, thereby increasing the welding current. When switching to the second voltage level, the coil is preferably connected directly between the outputs of the welding power source, thus supplying power to the welding process. To switch to the second voltage range, the two terminals of the power supply can be connected together, for example, via a low electrical resistance, such as the through-resistance of a FET. This reduces the energy stored in the coil by the flowing welding current, causing the welding current to decrease.

[0061] In one embodiment, in particular of the method, the welding process involves operating the arc with a current characteristic curve that has several welding cycles, each with at least one high-current phase and one low-current phase.

[0062] The coil is operated in saturation during the welding process, i.e., after ignition, preferably at least intermittently, and more preferably continuously. This enables rapid current control in the high-current range. The current control described above, via the electronic switching unit, allows for reliable current regulation despite the coil's low inductance during saturation operation. Preferably, the welding current during the welding process is at least intermittently greater than 150 A, more preferably greater than 200 A, and particularly greater than 250 A, especially during the high-current phase.

[0063] In one embodiment, particularly the orbital welding device, the orbital welding device comprises a welding head with a receptacle for positioning a joining area of ​​two joining partners, at least tubular in the joining area, in particular a fitting and a pipe end. Preferably, the orbital welding device further comprises an electrode drive configured to move a welding electrode circumferentially around the receptacle. More preferably, one of the first and second outputs of the welding power source is electrically connected to the welding electrode or a holder for a welding electrode for a welding operation, and the other of each of the first and second outputs is electrically connected to a contacting means for contacting a joining partner. The contacting means may, in particular, comprise a contacting element.

[0064] The orbital welding device's welding head is designed to position a joining area between two components that are at least tubular in shape. Each component has a joining area where it is to be welded together. In the case of a push-on fitting, the fitting's joining area can, for example, include a region at the fitting opening, and the joining area of ​​the pipe end to be welded to it can include the portion of the pipe end that, when the fitting is pushed on, is located at the fitting opening. In the case of a push-in fitting, the fitting's joining area can, for example, include a region at a stop edge for a pipe end, and the joining area of ​​the pipe end to be welded to it can include the portion of the pipe opening that, when the fitting is inserted, abuts the stop edge.The joining area of ​​the fitting and the joining area of ​​the pipe end, or more generally, the respective joining areas of the two components, together form the joining area of ​​the two components. In addition to these two components, further components can also be provided.

[0065] In one embodiment of the orbital welding device, a control unit is provided that is configured to control the orbital welding device such that a weld seam is produced by means of the welding electrode on two joining partners arranged in the holder, consisting of a circumferentially extending chain of joining points. For this purpose, the control unit preferably comprises at least one processor and at least one memory containing instructions, the execution of which on the at least one processor results in corresponding control of the orbital welding device. The memory can, for example, be a ROM memory or a RAM memory. In particular, the control unit of the orbital welding device can control the welding power source and / or the electrode drive.

[0066] The control unit of the orbital welding device and the preferably provided control unit of the welding power source can be identical; that is, the control unit of the orbital welding device can also be the control unit of the welding power source, or vice versa. Furthermore, it is conceivable that different control units are provided.

[0067] In one embodiment, particularly the orbital welding device, the device comprises a handheld unit that includes the welding head and preferably a handle connected to the welding head. Preferably, the welding power source and the control unit can also be housed in the handheld unit. Furthermore, the handheld unit can have a battery or accumulator, a receptacle or connection for one, particularly for a replaceable accumulator. For example, a connection for plugging in a replaceable accumulator can be provided. This enables flexible and easy operation of the orbital welding device even under confined working conditions.

[0068] Preferably, the orbital welding device is designed entirely as a handheld unit, in particular with an integrated or attachable battery, especially a replaceable battery. This allows for particularly flexible and easy use of the orbital welding device.

[0069] It is also conceivable that the orbital welding device, in addition to the handheld unit, includes at least one case or backpack, connected to the handheld unit, for example, via a hose package, in which components of the orbital welding device, such as the welding power source and / or a battery or accumulator, or a holder for one, are located. In this way, the handheld unit can be designed to be more compact and lighter, thus simplifying its operation. At the same time, the orbital welding device remains portable.

[0070] In one embodiment, the welding head has a first opening and a second opening opposite the first opening, between which the receptacle extends longitudinally. In this way, two joining partners, in particular a fitting and a pipe end, which are to be arranged in the receptacle with their joining area, can extend out of the first and second openings.

[0071] The welding head surrounds the receiver, particularly at least partially, in an azimuthal direction.

[0072] The first and second openings can be connected to each other. In particular, the welding head can be adjustable between an open position and a closed position, wherein in the open position the welding head has an insertion opening connecting the first and second openings for inserting a joining area of ​​two joining partners, which are at least tubular in the joining area, into the receptacle, and wherein the insertion opening is at least partially closed in the closed position.

[0073] The insertion opening forms, in particular, an azimuthal insertion area. This allows the two joining partners, with their joining area in the open position, to be inserted through the insertion opening into the receptacle. This means the welding head can be placed laterally onto the joining partners, especially a pipe end and a fitting, particularly if they are already arranged relative to each other, for example, nested together. In the closed position, the two joining partners, with their joining area, can be fixed in the receptacle. Preferably, the insertion opening is completely closed in the closed position. This provides better protection for the user against UV radiation and welding fumes. Furthermore, the escape of shielding gas can be largely prevented.

[0074] In one embodiment, the orbital welding device comprises an adjustment mechanism and a locking mechanism for actuating the adjustment mechanism, wherein the adjustment mechanism is configured to move the welding head between the open and closed positions. The locking mechanism is preferably mechanically operable. The adjustment mechanism can, in particular, comprise one or more locking ring segments, preferably driven in opposite directions.

[0075] In one embodiment, the orbital welding device comprises an electrode recirculation mechanism and an electrode drive, in particular a motor, for driving the electrode recirculation mechanism, wherein the electrode recirculation mechanism is configured to move the electrode holder or welding electrode circumferentially around the holder. In this way, the welding electrode can be moved automatically and in a controlled manner circumferentially around the joining area of ​​the joining partners arranged in the holder during the orbital welding process in order to weld them together, in particular by means of a chain of joining points.

[0076] In one embodiment, particularly the orbital welding device, the welding head has a fitting fixing contour designed to engage with a corresponding outer contour of the fitting, especially when the welding head is closed and the joining area of ​​a fitting is arranged in a predetermined fitting position within the welding head receptacle, such that the joining area of ​​the fitting is held in a predetermined fitting position. In one embodiment of the system, the fitting has an outer contour corresponding to the fitting fixing contour.

[0077] In the predetermined fitting position, the fitting opening or an edge of the fitting assumes a predetermined position relative to the electrode ring segment or the welding electrode, particularly at a predetermined distance from the tip of the welding electrode. This predetermined distance can be, for example, a maximum of 1.2 mm, preferably a maximum of 1.1 mm. More specifically, the predetermined distance can be in the range of 0.15–1.2 mm, preferably 0.25–1.1 mm, and more preferably 0.35–1.0 mm. Preferably, the welding electrode maintains the predetermined distance or distance range to the fitting opening in every rotational position of the welding electrode, so that the orbital welding process can be carried out with a very small distance between the welding electrode and the fitting opening. In this way, the welding process can be carried out with a short arc length and low energy consumption and heat input into the fitting or pipe end.

[0078] In one embodiment, particularly when the fitting is a push-on fitting, the predetermined fitting position is such that the tip of the welding electrode has a radial distance to the outer surface of the pipe end in the range of 0.3–1.5 mm, preferably 0.4–1.4 mm, more preferably 0.5–1.3 mm, particularly 0.60–0.80 mm, and / or an axial distance to the welding edge or stop edge in the range of 0.15–1.2 mm, preferably 0.25–1.1 mm, more preferably 0.35–1.0 mm, particularly 0.40–0.70 mm. In this embodiment, the welding electrode is preferably oriented obliquely inwards with respect to the longitudinal direction.

[0079] In one embodiment, particularly when the fitting is a push-fit fitting, the predetermined fitting position is such that the tip of the welding electrode has a radial distance from the outer surface of the pipe end and / or the outer surface of the fitting in the range of 0.3–1.5 mm, preferably 0.4–1.4 mm, and more specifically 0.40–0.80 mm. In this embodiment, the welding electrode is preferably oriented radially inwards with respect to the longitudinal direction.

[0080] In one embodiment, particularly the orbital welding process, two joining partners, at least in one joining area tubular, are arranged relative to each other, especially in a lap joint, and a chain of joining points extending circumferentially to the joining partners is created in the joining area, which connects the joining partners by a material bond. The chain of joining points is preferably created in a single welding operation, preferably without an intermediate ignition operation. In particular, several joining points are preferably created after an ignition operation without an intermediate ignition operation.

[0081] During the welding process, the welding electrode is preferably moved in a circumferential direction around the fixture, for example between or during the creation of the individual joining points.

[0082] In one embodiment, the joining points are placed side by side, overlapping. This ensures a reliably liquid-tight weld. In another embodiment, the joining points are created using a welding electrode guided circumferentially around the joining partners. The tip of this electrode preferably has a distance to the joining partners of a maximum of 1.5 mm, more preferably a maximum of 1.4 mm, more preferably a maximum of 1.3 mm, and particularly a maximum of 1.2 mm. This distance of the welding electrode to the joining partners of a maximum of 1.5 mm, more preferably a maximum of 1.2 mm, allows for more precise positioning of the joining point. Furthermore, the arc length is reduced, thereby minimizing heat loss and reducing the overall energy required for the welding process.By maintaining a preferably minimum distance of 0.15 mm, more preferably 0.25 mm, even more preferably 0.35 mm, and in particular 0.4 mm, immersion of the welding electrode in the weld pool can be avoided.

[0083] Further features and advantages of the welding power source, the method for its operation, the orbital welding device, the system and the orbital welding process will become apparent from the following description of exemplary embodiments, with reference to the accompanying drawing.

[0084] The drawing shows

[0085] Fig. 1 shows a first embodiment of the orbital welding device,

[0086] Fig. 2a-d shows the welding head of the orbital welding device from Fig. 1,

[0087] Fig. 3 shows a schematic block representation of the functional components of the orbital welding device from Fig. 1.

[0088] Fig. 4 shows a schematic block representation of the welding power source of the orbital welding device from Fig. 1.

[0089] Fig. 5a-b shows a schematic representation of the creation of a joining point in the orbital welding process, Fig. 6a-c shows an embodiment of the orbital welding process on a fitting and a pipe end,

[0090] Fig. 7 shows another embodiment of the orbital welding device,

[0091] Fig. 8 shows a more detailed schematic block representation of the welding power source from Fig. 1.

[0092] Fig. 9 Time diagrams of different voltage and current intensities during the ignition process of an embodiment of the orbital welding process and

[0093] Fig. lOa-c shows a schematic block diagram and diagrams illustrating welding current control according to a welding current characteristic curve in an embodiment of the orbital welding process.

[0094] Fig. 1 shows a schematic representation of an embodiment of the orbital welding device.

[0095] The orbital welding device 100 is designed as a mobile welding device in the form of a handheld unit 102. In the present embodiment, the handheld unit 102 comprises all components of the orbital welding device 100, making the orbital welding device 100 very flexible to handle, even under difficult installation conditions.

[0096] The handheld device 102 comprises a welding head 104, which has a receptacle 106 in which a joining area of ​​two joining partners, for example a pipe end and a fitting, can be arranged. The handheld device 102 further comprises a handle 108 with a shaft 110 on which the welding head 104 is arranged, and a grip 112 for holding and operating the handheld device 102. The grip 112 has a connection 114 at its end opposite the shaft 110 for an interchangeable accumulator unit 116. The shaft 110 further has a connection 115 for an interchangeable shielding gas magazine 120.

[0097] The handle 108 houses various components for operating the orbital welding device 100, namely, in particular, an adjustment mechanism 122 for adjusting the welding head 104 between an open and a closed position, an electrode drive 124 for driving a welding electrode 126 in the welding head 104, a welding power source 128 for providing the ignition voltage and welding current for the orbital welding process, a control unit 130 for controlling the orbital welding device 100, a valve 132 for controlling the shielding gas supply, and a user interface 134 comprising display and operating elements 136 for configuring the orbital welding device 100, as well as a torch trigger 138 for starting an orbital welding process. Furthermore, the accumulator unit 116 includes an accumulator 140, for example, a lithium-ion accumulator, and the shielding gas magazine 120 includes a shielding gas container 142.

[0098] Figures 2a-d show the welding head 104 of the orbital welding device 100 in a schematic, perspective view, in the open position (Fig. 2a), in the open position after arranging a joining area 150 of two joining partners, namely a fitting 152 and a pipe end 154, in the receptacle 106 (Fig. 2b), as well as in the closed position before (Fig. 2c) and during the execution of an orbital welding process (Fig. 2d).

[0099] The welding head 104 has a fixed part 160, which circumferentially surrounds the receptacle 106, and a movable part 162. In the open position, the movable part 162 is at least partially retracted into the fixed part 160, exposing an insertion opening 164 in the circumferential direction. In the closed position, the movable part 162 closes the insertion opening 164, so that the receptacle 106 is essentially completely closed in the circumferential direction. In the axial direction (longitudinal direction), the receptacle 106 extends between a first opening 166 and a second opening 168.

[0100] To adjust the welding head 104 between the open and closed positions, an adjustment mechanism 170 is provided on the welding head 104. Furthermore, an electrode circulation mechanism 172 is provided on the welding head 104, with which the welding electrode 126 can be moved circumferentially around the receptacle 106 in the closed position of the welding head 104 for carrying out an orbital welding process.

[0101] Fig. 3 shows a schematic block diagram of the functional components of the orbital welding device 100 from Fig. 1. The accumulator 140 supplies all electrical components of the orbital welding device 100 with electrical energy. In particular, the accumulator 140 supplies the welding power source 128, the control unit 130 and the electrode drive 124.

[0102] The welding power source 128 provides the ignition voltage for arc ignition and the welding current for the orbital welding process. For this purpose, the welding power source 128 has two outputs 174, 176, one of which is electrically conductively connected to the welding electrode 126 during an orbital welding process, and the other is electrically conductively connected to one or more contacting elements 178 for contacting a joining partner arranged in the receptacle 106.

[0103] The electrode drive 124 preferably has an electric motor and is connected, for example via an axis 180, to the electrode recirculation mechanism 172 in order to transmit the movement, for example a rotary movement, from the electric motor to the electrode recirculation mechanism 172, so that the electrode recirculation mechanism 172 moves the welding electrode around the receptacle 106.

[0104] The control device 130 is designed to control the orbital welding device 100 and for this purpose may in particular have at least one microprocessor 182 and a memory 184 with instructions, the execution of which on the at least one microprocessor 182 effects the control of the orbital welding device 100.

[0105] Furthermore, the control unit 130 is connected to the user interface 134 to output user output, for example via a screen included by the display and control elements 136, and to receive user input, for example via buttons or touchscreen included by the display and control elements 136 or from the burner button 138.

[0106] The control unit 130 is specifically designed to control an orbital welding process. For this purpose, the control unit 130 is connected to the electrode drive 124, the valve 132 for controlling the shielding gas flow to the welding head 104, and the welding power source 128.

[0107] In the present embodiment, the adjustment mechanism 122 is mechanically designed, allowing a user to manually actuate the adjustment mechanism 170 to move the welding head 104 between the closed and open positions. Alternatively, or additionally, the adjustment mechanism 122 could be motorized, for example, by having an electric motor controllable via the control unit 130, so that the welding head 104 can be automatically adjusted between the closed and open positions. The shielding gas reservoir 142, which contains a shielding gas, in particular an inert gas, and is preferably replaceable, is connected to the welding head 104 via the valve 132. The welding head 104 preferably has a shielding gas guide to deliver the shielding gas to the area of ​​the welding electrode 126 for the orbital welding process.

[0108] Fig. 4 shows a schematic block diagram of the functional components and connections of the welding power source 128. The welding power source 128 has two inputs 186, 188 for connecting the two poles of the accumulator 140 and two outputs 174, 176 for providing the ignition voltage and the welding current and for electrically conductive connection with the contacting element 178 and the welding electrode 126.

[0109] The welding power source 128 has an electronic circuit 190 which is supplied by the voltage, in particular DC voltage, applied to the inputs 186, 188 and can provide an ignition voltage for igniting an arc and a welding current for supplying an arc welding process via the outputs 174, 176. The electronic circuit 190 can, for example, comprise one or more electronic switches, in particular a half-bridge circuit, and preferably at least one coil.

[0110] The electronic circuit 190 can further include its own control device, for example a microprocessor, which controls the operation of the welding power source 128, in particular by controlling one or more switches of the electronic circuit 190.

[0111] The electronic circuit 190 is functionally configured to provide a high-voltage pulse at outputs 174 and 176 for igniting the welding arc. This is illustrated in Fig. 4 by the functional module HV ignition 194. Furthermore, the electronic circuit 190 is configured to provide welding current control, allowing the current intensity of a welding current flowing through outputs 174 and 176, i.e., the welding current intensity, to be regulated, particularly according to a predefined current characteristic. This is illustrated in Fig. 4 by the functional module welding current control 192.

[0112] Accordingly, the control unit of the welding power source 128 can be configured, in particular, to generate a high-voltage pulse to ignite a welding arc and subsequently to provide a welding current for an orbital welding process, and in particular to regulate the welding current. The control unit of the welding power source 128 is preferably configured to regulate the welding current according to a predetermined or predefinable welding current characteristic curve when the arc is burning.

[0113] The welding power source 128 can be connected to, or is connected to, the control unit 130 and can thus be controlled by the control unit 130. In particular, the control unit 130 can control the control unit of the welding power source 128 in order to initiate and / or configure the control of the operation of the welding power source 128 by the control unit of the welding power source 128.

[0114] Instead of two separate control units, it is also conceivable that the control unit 130 and the control unit of the welding power source 128 are designed as a common control unit, for example as a microprocessor.

[0115] The following explains the execution of an orbital welding process with the orbital welding device 100, namely the execution of an orbital welding process on a pipe end 154 and a fitting 152.

[0116] Figures 5a and 5b each show a schematic cross-sectional view of the joining area 150 of fitting 152 and pipe end 154 arranged in the welding head 104, with the figures showing only the upper half. Some of the components of the welding head 104 are shown with dashed lines.

[0117] The fitting 152 is pushed onto the pipe end 154, as shown in Fig. 5a. For this purpose, the inner cross-section of the fitting 152 is preferably adapted to the outer cross-section of the pipe end 154 in such a way that only a small gap remains between the outer wall of the pipe end 154 and the inner wall of the fitting 152.

[0118] The overlap joint formed in this way between pipe end 154 and fitting 152 forms the joining area 150, in which fitting 152 and pipe end 154 are to be welded together.

[0119] To perform the orbital welding process, the welding head 104 is first moved to the open position via the adjustment mechanism 122, so that the movable part 162 of the welding head 104 exposes the insertion opening 164 (Fig. 2a). The hand-held device 102 with the welding head 104 can then be placed laterally with the insertion opening 164 onto the joining area 150 of the pipe end 154 and the fitting 152 pushed onto it, so that the joining area 150 is arranged in the receptacle 106 (Fig. 2b), while the remaining part of the fitting 152 and the remaining part of the pipe end 154 extend out of the receptacle 106 through the openings 166, 168.

[0120] The welding head 104 is then moved into the closed position via the adjustment actuator 122 (Fig. 2c). In the closed position, the joining area 150 of the pipe end 154 and the fitting 152 is preferably fixed in the receptacle 106 by the stationary part 160 and the movable part 162 of the welding head 104 by means of a positive and / or non-positive locking mechanism, particularly in the axial direction and more preferably also in the azimuthal direction. Furthermore, this fixing preferably also aligns the pipe end 154 and the fitting 152, and most preferably centers the pipe end 154 in the fitting 152. In Fig. 5a, the contours 200, 202 fixing the fitting 152 and the pipe end 154 are shown schematically with dashed lines. The fixing is achieved in particular by the joining area 150 being arranged in the area of ​​the welding electrode 126.The welding electrode 126 is directed obliquely inwards, in particular at an angle to the radial direction in the range of 5–45°, for example 45°, and can be directed obliquely in the circumferential direction, i.e., in the welding direction, for example at an angle in the range of 0–15° to the radial direction. In the arrangement shown in Fig. 5a, the tip of the welding electrode 126 points towards the overlap joint. The contours 200, 202 can, in particular, at least partially form one or more contacting elements 178 for electrically connecting the fitting 152 and the pipe end 154 to an output of the welding power source 128.

[0121] The contours 200 are specifically adapted to the outer contour of the fitting. The contours 200, 202 that fix the fitting 152 and the pipe end 154 can be designed, in particular, to clamp the fitting 152 and the pipe end 154, especially to hold them in a force-fit position. Such fixation of the fitting 152 and / or the pipe end 154 ensures reliable electrical contact between the fitting 152 and the pipe end 154.

[0122] The orbital welding device 100 with the welding head 104 and the fitting 152 form a system 700.

[0123] In the closed position of the welding head 104, the joining area 150 is preferably completely enclosed in the circumferential direction, so that the shielding gas supplied during the orbital welding process is retained in the joining area 150 and the surroundings, in particular the user, are protected from welding fumes and UV light generated during the orbital welding process. After adjusting the welding head 104 to the closed position, the user can trigger the start of the orbital welding process, for example by pressing the torch trigger 138. The control unit 130 controls the electrode drive 124 and the welding power source 128 such that the welding electrode 126 creates a chain 211 of weld points 210 in the circumferential direction, which materially join the fitting 152 and the pipe end 154.

[0124] Figures 5a-b schematically illustrate the creation of a joint 210. To create a first joint 210, the welding power source 128 initially generates a high-voltage pulse, which causes a contactless ignition of an arc between the welding electrode 126 and the fitting 152 or pipe end 154. Subsequently, the welding power source 128 regulates the welding current according to a welding current characteristic curve, which includes, in particular, a sequence of high-current and low-current phases. During the high-current phases, the heat input caused by the arc leads to the formation of a molten pool (also referred to as a weld pool) at the overlap joint of fitting 152 and pipe end 154, which at least partially solidifies during the low-current phase and forms a joint 210.To ensure that the next weld point is offset circumferentially from the previous weld point, the control unit 130 activates the electrode drive 124, causing it to move the welding electrode 126 circumferentially. During the next high-current phase, the welding power source 128 melts a new weld pool for the adjacent weld point, which preferably overlaps with the first weld point. A new ignition is not required for the second and subsequent weld points, as the arc preferably burns continuously until the last weld point.

[0125] In this way, the chain 211 of joining points 210 is gradually created, by which fitting 152 and pipe end 154 are preferably fluid-tightly connected to each other at the overlap joint. Figures 6a-b show the creation of the joining points 210 in schematic sectional views corresponding to the section plane labeled "Via" in Figure 5a, where Figure 6a shows a point in time during the ongoing orbital welding process and Figure 6b shows a point in time after completion of the orbital welding process. Figure 6c shows a perspective view of the finished joint (weld) of fitting 152 and pipe end 154.

[0126] After the weld has been completed, the welding power source 128 reduces the welding current to zero, extinguishing the arc. By actuating the adjustment mechanism 122, the user can then return the welding head 104 to the open position and remove the welding head 104 laterally from the now materially bonded fitting 152 and pipe end 154.

[0127] Fig. 7 shows another embodiment of the orbital welding device. The orbital welding device 101 has a similar structure and function to the orbital welding device 100. Functionally corresponding components are therefore provided with the same reference numerals, even if they may be arranged or designed differently in some respects, and reference is made to the description of Figs. 1-6c above.

[0128] The orbital welding device 101 differs from the orbital welding device 100 in that some components, namely the shielding gas cylinder 142 and the accumulator 140 in Fig. 7, are designed separately from the handheld device and connected to it by corresponding gas and electrical lines. This allows the handheld device to be designed more compactly and lighter.

[0129] Furthermore, larger inert gas cylinders 142 and accumulators 140 can be used in this way. The inert gas cylinder 142 and the accumulator 140 can, for example, be arranged in a separate case or backpack.

[0130] Instead of a battery, a mains connection can also be provided to supply power to the handheld device 102 of the welding power source 128. This allows for longer operation, albeit with less flexibility in handling. Fig. 8 shows a more detailed schematic block diagram of the welding power source 128.

[0131] As already explained with reference to Fig. 4, the welding power source 128 has a first and second input 186, 188 for connecting a DC voltage source, such as the accumulator 140, as well as a first and second output 174, 176 for supplying an arc welding process. Furthermore, the welding power source 128 includes the electronic circuit 190, which is supplied via the inputs 186, 188 and can provide an ignition voltage for igniting an arc and a welding current for supplying an arc welding process via the outputs 174, 176.

[0132] The welding power source 128 has its own control unit 198, which is connected to the control unit 130. As previously explained, the control unit 130 and the control unit 198 of the welding power source 128 can also be configured as a single, combined control unit.

[0133] The welding power source 128, or rather the electronic circuit 190 of the welding power source 128, now comprises a coil 604, which has a first coil terminal 606, an intermediate tap 608, and a second coil terminal 610. A first winding section 612 of the coil 604 is connected between the first coil terminal 606 and the intermediate tap 608, and a second winding section 614 of the coil 604 is connected between the intermediate tap 608 and the second coil terminal 610. The first and second winding sections 612, 614 are arranged axially offset side by side on a coil core 616, for example, a ferrite core, which has a gap 618 located within the second winding section 614 and is closed by means of two legs 620, 622 outside the first and second winding sections 612, 614.

[0134] The first winding section 612 has a number of turns Ni and an inductance Li. The second winding section 614 has a number of turns N2 and an inductance L2. In the present embodiment, for example, Ni = 3 and N2 = 10, resulting, for example, in an inductance ratio L2 / L1 > 3.

[0135] The welding power source 128 further comprises a power supply 624, which has a first and second terminal 626, 628 as outputs and is configured to modify the voltage applied to the first and second inputs 186, 188 and provide it via the terminals 626, 628. For this purpose, the power supply 624 comprises an electronic switching unit 196, preferably with a half-bridge circuit 197, the output of which is connected to the first terminal 626 and which, during operation, preferably provides a pulsed voltage at the terminals 626, 628, in particular a voltage that switches back and forth between 0 V or a voltage range around 0 V, for example 0–1 V, and a voltage value Uack or a voltage range around Uack. Uack preferably corresponds to the voltage applied to the inputs 186, 188 or to the battery voltage.Uakk can also correspond to the voltage of an optional DC voltage converter, in particular a boost converter, powered via inputs 186, 188 or the accumulator.

[0136] For operation, the accumulator can, for example, be connected with its positive terminal to input 186 and with its negative terminal to input 188. The potential at input 188 can be considered, for example, as a reference potential of 0V (virtual ground). The potential Uakk is then present at input 186.

[0137] The half-bridge circuit 197 comprises two electronic switches S1 and S2, which are implemented as FETs. The power supply 624 can apply the potential from input 186 to the first terminal 626 of the power supply 624 by closing switch S1 and opening switch S2, and the potential from input 188 by closing switch S2 and opening switch S1, so that the voltage between the first and second terminals 626, 628 of the power supply 624 can be switched back and forth between 0 V and Uakk. Furthermore, the welding power source 128 includes an electronically controllable intermediate tap switch 644, which can include, for example, a FET 646, in particular a SiC-FET, and a gate-side driver circuit 648, with which the gate-source voltage of the FET 646 can be switched back and forth between a voltage UGS_O opening the FET 646 and a voltage UGS_I closing the FET 646.

[0138] The control unit 198 of the welding power source 128 is designed to control the welding power source 128, in particular to control the electronic switching unit 196, for example to switch the electronic switching elements S1 and S2 of the half-bridge circuit 197 and to control the intermediate tap switch 644 and is connected to these for this purpose.

[0139] The first terminal 626 of the power supply 624 is electrically connected to the first coil terminal 606 of the coil 604. Furthermore, the intermediate tap 608 of the coil 604 is electrically connected to the second terminal 628 of the power supply via the intermediate tap switch 644. In this way, the welding power source 128 is connected such that the first winding 612 of the coil 604 is connected between the terminals 626 and 628 of the power supply 624 via the intermediate tap 608 and the intermediate tap switch 644.

[0140] The second coil terminal 610 of the coil is electrically connected to the first output 174 of the welding power source 128, and the second output 176 of the welding power source 128 is electrically connected to the second terminal 628 of the power supply 624. In this way, the welding power source 128 is connected such that the first and second windings 612, 614 of the coil 604 are connected via the second coil terminal 610 and the outputs 174, 176 of the welding power source 128 between the terminals 626, 628 of the power supply 624. One or more diodes 652, in particular SiC or Schottky diodes, one of which is shown in Fig. 8, are connected between the intermediate tap 608 of the coil 604 and the intermediate tap switch 644. The one or more diodes 652 have in particular a reverse recovery time of preferably less than 50 ns.

[0141] A capacitor 654 is preferably connected between the first and second outputs 174, 176 of the welding power source 128, for example in the form of one or more capacitors, one of which is shown by way of example in Fig. 8.

[0142] Furthermore, a welding current sensor 656 is provided, with which measured values ​​for the welding current flowing via outputs 174 and 176 can be measured. The welding current sensor 656 can be, for example, a Hall sensor or a current-sensing resistor. The control unit 198 is connected to the welding current sensor 656 to determine measured values ​​for the welding current. In this way, the control unit 198 can, in particular, regulate the welding current as a function of the measured values ​​for the welding current with the welding current sensor 656.

[0143] The welding electrode 126 or the electrode holder therefor, and the one or more contacting elements 178 for contacting a joining partner arranged in the receptacle 106 of the orbital welding device 100, are each connected to an output 174, 176 of the welding power source 128. In Fig. 8, for example, the welding electrode 126 or the electrode holder therefor is connected to the second output 176, and the one or more contacting elements 178 are connected to the first output 174. A distance 668 lies between the welding electrode 126 and the workpiece contacted during operation by the one or more contacting elements 178. An arc is to be ignited over this distance during operation and burn for a welding process. The operation of the welding power source 128 and the orbital welding device 100 with this welding power source 128 is described below with reference to Fig. 9 and Fig. 10a-c.Figure 9 first illustrates a high-voltage ignition system for igniting the welding arc. Figures 10a-c then illustrate a welding current control system for carrying out the orbital welding process after ignition of the welding arc.

[0144] Figure 9 shows three diagrams over a common time axis. The diagrams are labelled (a), (b) and (c) respectively on the right-hand side; hereafter, the individual diagrams will be referred to accordingly as Fig. 9(a), Fig. 9(b) and Fig. 9(c). Fig. 9(a) shows the gate-source voltage Ucs(t) produced by the gate-side driver circuit 648 to control the FET 646, Fig. 9(b) shows the current IzA(t) flowing through the first winding section 612 and the intermediate tap switch 644, and Fig. 9(c) shows the voltage Uout(t) between the first and second outputs 174, 176 of the welding power source 128.

[0145] In an orbital welding process using the orbital welding device 100 (or 101), a joining area of ​​two workpieces, namely in particular a fitting and a pipe, is first arranged in the area of ​​the welding electrode 662, and one or both of the workpieces are contacted with the contacting means 664. Subsequently, the control unit 130, for example upon receiving a corresponding user input via the user interface 134, starts a welding process and controls the control unit 198 of the welding power source 128 for this purpose.

[0146] The control unit 198 controls the welding power source 128 such that an ignition process is carried out. During the ignition process, the control unit 198, by appropriately controlling the driver circuit 648, causes the intermediate tap switch 644 to close at time to. Furthermore, the control unit 198, by controlling the switching unit 196, causes the potential Uakk to be applied to the first coil terminal 606 from time ti. Preferably, ti > to. As a result, from time ti, a coil ignition voltage approximately equal to the battery voltage is present between the first coil terminal 606 and the intermediate tap 608. This causes a current to flow through the first winding 612 of the coil 604, the intermediate tap 608, and the intermediate tap switch 644 with increasing current IzA(t), as shown in Fig. 9(b).

[0147] After a time interval At has elapsed since the start of the current flow through the first winding section 612, i.e., at time t2 in Fig. 9, the control device 198 causes the intermediate tap switch 644 to open, thus interrupting the current flow through the intermediate tap 608. The current IzA(t) flowing through the intermediate tap 608 and the intermediate tap switch 644 therefore drops abruptly. This change in current causes a significant voltage increase at the intermediate tap 608 due to the inductance of the first winding section 612 of the coil 604. This voltage increase, amplified by the ratio L2 / L1 of the inductances, leads to an even greater voltage increase at the second coil terminal 610, resulting in voltage spikes sufficient to ignite an arc across the path 668, as shown in Fig. 9(c).

[0148] The inductance of coil 604 and the capacitance 654, together with any existing resistances such as line resistances, form a damped resonant circuit, wherein the capacitance 654 is preferably selected such that the frequency of the resonant circuit is in the range of 1–2 MHz. This results in a decaying high-frequency voltage pulse across the path 668 at time t2, which ignites the arc.

[0149] In this way, the coil 604 and the intermediate tap switch 644, together with the control described above by the control device 198, ensure that the electronic circuit 190 functionally provides an HV ignition 194.

[0150] Figures 10a-c illustrate the operation of the welding power source 128 for carrying out a welding process after arc ignition. Figure 10a shows a schematic representation of the components of the welding power source 128 involved in regulating the welding current. Figure 10b shows a diagram illustrating the control of the electronic switching unit 196 by the control device 198. Figure 10c shows a diagram in which the current characteristic of the welding process following the ignition process is plotted against time.

[0151] After the welding arc is ignited, the intermediate tap switch 644 remains open. Therefore, no current flows through the intermediate tap switch 644 during welding current regulation, so that current flows through both windings 612, 614 of the coil 604 and the coil 604 behaves like a normal two-pole coil.

[0152] The control unit 198 controls the switching unit 196 for welding current control based on the measured values ​​for the welding current hoad obtained from the welding current sensor 656. Fig. 10a shows an example of the logic implemented in the control unit 198 for carrying out the welding current control. In this example, the welding current sensor 656 provides a measured voltage Ucurrent, proportional to the welding current hoad, as the measured value for the welding current. In the control unit 198, this measured voltage Ucurrent is compared with an upper threshold voltage Uhigh and a lower threshold voltage Uiow, respectively, using a comparator 670 or 671. These voltages correspond to an upper and lower threshold welding current, respectively. The threshold voltages Uhigh and Uiow are selected such that they lie above and below a voltage Uset, respectively, which corresponds to the current target welding current according to the current characteristic curve.

[0153] Fig. 10b shows a possible course of the measurement voltage Ucurrent over time during welding current control.

[0154] If the measured voltage Ucurrent exceeds the upper threshold voltage Uhigh, the comparator 670 outputs a voltage signal Ucompi.out to a switching logic 672 implemented in the control unit 198. This voltage signal Ucompi.out causes the switching logic 672 to open the switching element S1 and close the switching element S2. As a result, the first coil terminal 606 is pulled to the potential of the second terminal 628, or the second output 176. Thus, the coil 604, with its two coil terminals 606 and 610, is effectively directly connected to the outputs 174 and 176, and the welding process is powered by the energy stored in the coil 604. The energy stored in the coil 604, and consequently the welding current flowing through the coil 604 and the outputs 174 and 176, decreases, which also reduces the measured voltage Ucurrent.

[0155] If the measured voltage Ucurrent falls below the lower threshold voltage Ui OWj, the comparator 671 outputs a voltage signal Ucom. P 2_out is sent to the switching logic 672, which causes it to open switching element S2 and close switching element S1. This results in the first coil terminal 606 being pulled to Uakkb, or the potential of the first input 186, so that coil 604 and the accumulator 140 connected to inputs 186 and 188 are effectively connected in series between outputs 174 and 176. The energy stored in the accumulator 140 then powers the welding process and increases the welding current, which in turn increases the energy stored in coil 604. The rising welding current also causes the measuring voltage Ucurrent to rise again.

[0156] The opening of switch SI or S2 is indicated in Fig. 10b in the row belonging to the respective switch as “0” and the closing as “1”.

[0157] The control logic described with reference to Fig. 10a-b thus allows for simple and robust welding current control. It has been found that this welding current control enables reliable regulation of the welding current even with fluctuating loads between outputs 174 and 176, for example, with varying arc lengths.

[0158] The comparators 670, 671 and the switching logic 672 are shown as separate functional units in Fig. 10a. Alternatively, these functional units can also be integrated into a single circuit. It is also conceivable to implement the comparators 670, 671 and / or the switching logic 672 at least partially using analog electronic components. For example, the comparators 670, 671 can be implemented using operational amplifiers.

[0159] Fig. 10c shows a current characteristic curve Iset(t) for controlling the welding process after the arc ignition at time t2, as previously described with reference to Fig. 9. After arc ignition, the control unit 198 initiates a welding process in which the arc is operated with the current characteristic curve shown in Fig. 10c. For welding current control according to this current characteristic curve, the control unit 198 is specifically configured to adjust the values ​​of Uset, Uiow, and Uhigh for the welding current control described with reference to Figs. 10a-b in such a time-dependent manner that the welding current is controlled to the current target welding current Iset(t) according to the current characteristic curve, thus ensuring a corresponding welding current.

[0160] The current characteristic curve comprises a warm-up phase (#0) and several successive welding cycles (#1, #2, #3 ...), each with a high-current phase (Athot) and a low-current phase (Atcoid). Compared to the welding cycles, the warm-up phase features an extended high-current phase (At°hot) with a reduced high-current phase current I°hot. During this phase, the joining partners are preheated. Optionally, the initial weld pool for the first joining point (weld point) can be generated during the warm-up phase. As shown in Fig. 10c, the warm-up phase can, for example, include a low-current phase, for instance, to at least partially solidify a weld pool for the first joining point or as a relaxation phase to distribute the heat introduced during the high-current phase. The low-current phase of the warm-up phase can also be omitted, particularly if no weld pool is generated during the warm-up phase. In the subsequent welding cycles (#1, #2, #3 ...During each high-current phase of a welding cycle, a weld point is created, which then at least partially solidifies in the subsequent low-current phase of the same welding cycle before the next weld point is created in the following high-current phase. During the welding cycles (#1, #2, #3, ...), the electrode drive is controlled by the control unit 130 such that the welding electrode moves circumferentially around the joining partners, creating the individual weld points in an overlapping sequence. A weld point created in a high-current phase partially solidifies in the subsequent low-current phase before a new weld point is created. Since the arc continues to burn even in the low-current phases, no re-ignition is required between welding cycles.

[0161] The welding process described above can produce a weld seam from a circumferentially extending chain of welding points (joining points).

[0162] Reference symbol list:

[0163] 100, 101 Orbital welding device 102 Handheld device 104 Welding head 106 Mounting bracket 108 Handle 110 Shaft 112 Handle

[0164] 114 Connection for a battery unit

[0165] 115 Connection for a shielding gas magazine

[0166] 116 Accumulator unit 120 Shielding gas magazine 122 Adjustment mechanism 124 Electrode drive 126 Welding electrode

[0167] 128 Welding power source

[0168] 130 Control unit

[0169] 132 Valve

[0170] 134 User interface

[0171] 136 Display and Control Elements

[0172] 138 burner buttons

[0173] 140 accumulator

[0174] 142 protective gas cylinders

[0175] 150 joining area

[0176] 152 Fitting

[0177] 154 Pipe end

[0178] 160 fixed part

[0179] 162 moving part

[0180] 164 Insertion opening

[0181] 166 first opening

[0182] 168 second opening

[0183] 170 Adjustment mechanism

[0184] 172 Electrode circulation mechanism

[0185] 174, 176 outputs of the welding power source

[0186] 178 contact elements

[0187] 180 axis

[0188] 182 microprocessor

[0189] 184 storage

[0190] 186, 188 entrances

[0191] 190 electronic circuit

[0192] 192 Welding current control

[0193] 194 HV ignition

[0194] 196 electronic switching unit

[0195] 197 Half-bridge circuit

[0196] 198 Control unit, 202 contours

[0197] 210 Joining point

[0198] 211 Chain of joining points

[0199] 604 coil

[0200] 606 first coil connection

[0201] 608 Intermediate tap

[0202] 610 second coil connection

[0203] 612 first winding part of the coil

[0204] 614 second winding part of the coil

[0205] 616 coil core

[0206] 618 gap

[0207] 620 thighs

[0208] 624 Power supply, 628 Power supply connections

[0209] 644 Intermediate tap switch

[0210] 646 Field-effect transistor

[0211] 648 driver circuit

[0212] 652 diodes

[0213] 654 capacity

[0214] 656 Welding current measuring sensor

[0215] 662 Welding electrode

[0216] 664 Contacting means

[0217] 668 tracks, 671 comparators

[0218] 672 Switching logic

[0219] 700 System

Claims

Patent claims 1. Welding power source (128) for an orbital welding device (100, 101), with a first and second output (174, 176) for supplying an arc welding process of an orbital welding device (100, 101), characterized in that the welding power source (128) has a coil (604) which has a first coil connection (606), a second coil connection (610) and an intermediate tap (608), wherein a first winding part (612) of the coil (604) is electrically connected between the first coil connection (606) and the intermediate tap (608) and a second winding part (614) of the coil (604) is electrically connected between the intermediate tap (608) and the second coil connection (610).

2. Welding power source according to claim 1, characterized in that the welding power source (128) has a voltage supply (624) with two terminals (626, 628) and an electronically controllable intermediate tap switch (644), wherein the welding power source (128) is connected such that the first winding part (612) of the coil (604) can be switched or is switched between the terminals (626, 628) of the voltage supply (624) via the intermediate tap (608) and the intermediate tap switch (644), and that the first and second winding parts (612, 614) of the coil (604) can be switched or are switched between the terminals (626, 628) of the voltage supply (624) via the second coil terminal (610) and the outputs (174, 176) of the welding power source (128).

3. Welding power source according to claim 1 or 2, characterized in that the welding power source (128) has a voltage supply (624) with a first and a second connection (626, 628), that the first terminal (626) of the power supply (624) is electrically connected to the first coil terminal (606) of the coil (604), that the first output (174) is electrically connected to the second coil terminal (610) of the coil (604), that the second output (176) is electrically connected to the second terminal (628) of the power supply (624), and that the intermediate tap (608) is electrically connected to the second terminal (628) of the power supply (624) via an electronically controllable intermediate tap switch (644).

4. Welding power source according to one of claims 1 to 3, characterized in that the first and second winding part (612, 614) of the coil (604) are wound around a common coil core (616).

5. Welding power source according to claim 4, characterized in that the coil core (616) has a gap (618) in its longitudinal extension, which is preferably arranged within the second winding part (614).

6. Welding power source according to one of claims 1 to 5, characterized in that the coil core (616) is closed outside the coil (604).

7. Welding power source according to one of claims 1 to 6, characterized in that the inductance (L2) of the second winding part (614) is greater than the inductance (Li) of the first winding part (612), in particular that the ratio of the number of turns (N2) of the second winding part (614) to the number of turns (Ni) of the first winding part (612) is greater than 1, preferably greater than 2, in particular greater than 3.

8. Welding power source according to one of claims 1 to 7, characterized in that the intermediate tap switch (644) comprises a transistor, preferably a field-effect transistor, in particular a SiC field-effect transistor.

9. Welding power source according to one of claims 1 to 8, characterized in that one or more diodes (652) are connected between the intermediate tap (608) of the coil (604) and the intermediate tap switch (644), in particular with a reverse recovery time of less than 100 ns, preferably less than 50 ns.

10. Welding power source according to one of claims 1 to 9, characterized in that a capacitor (654) is connected between the first and the second output (174, 176), wherein the capacitor (654) between the first and second output (174, 176) is preferably adapted to the total inductance of the coil (604) such that they form a resonant circuit with a resonant frequency in the range of 0.5 - 2.5 MHz, in particular 1 - 2 MHz.

11. Welding power source according to one of claims 2 to 10, characterized in that the power supply (624) has a DC voltage source (140) or inputs (186, 188) for connecting a DC voltage source (140) and is configured to modify the voltage provided by the DC voltage source (140) or via the inputs (186, 188) and to provide the modified voltage via the terminals (626, 628) of the power supply (624).

12. Welding power source according to claim 10, characterized in that the power supply (624) has an electronic switching unit (196) which is configured to adjust the electrical voltage between the two terminals (626, 628) between to switch back and forth between at least two voltage ranges, in particular between a first voltage range of the DC voltage source (140) or the voltage applied to the inputs (186, 188) and a second voltage range, preferably in the range below 1 V.

13. Welding power source according to one of claims 1 to 12, characterized in that a welding current measuring sensor is provided for measuring measured values ​​for the welding current.

14. Welding power source according to one of claims 1 to 13, characterized in that a control device (130, 198) is provided which is configured to operate the welding power source (128) according to a method according to one of claims 15 to 20.

15. Method for operating a welding power source (128) according to one of claims 1 to 14, in which an arc ignition process is carried out, wherein during the arc ignition process a coil ignition voltage is applied between the first coil terminal (606) and the intermediate tap (608), so that an electric current flows through the first winding part (612) of the coil (604) via the first coil terminal (606) and the intermediate tap (608), in particular when the intermediate tap switch (644) is closed, and then the current flow via the intermediate tap (608) is interrupted, in particular by opening the intermediate tap switch (644).

16. Method according to claim 15, characterized in that after the ignition process a welding process with a burning arc is carried out between the first and the second output (174, 176), in particular with the intermediate tap switch (644) open.

17. Method according to claim 16, characterized in that current control is carried out during the welding process, in particular according to a predetermined or predefinable current characteristic curve.

18. Method according to claim 17, characterized in that the electrical voltage applied between the two terminals (626, 628) of the power supply (624) for current control is switched back and forth between at least two voltage values ​​depending on measured values ​​(Ucurrent) for the welding current (hoad), in particular switching to a first voltage value when the measured values ​​(Ucurrent) for the welding current (hoad) fall below a predetermined or predefinable lower threshold value, and switching to a second voltage value when the measured values ​​(Ucurrent) for the welding current (hoad) rise above a predetermined or predefinable upper threshold value.

19. Method according to claim 17 or 18, characterized in that during the welding process the arc is operated with a current characteristic curve which has several welding cycles with at least one high current phase and one low current phase.

20. Orbital welding device (100, 101) with a welding power source (128) according to one of claims 1 to 14.

21. Orbital welding device according to claim 20, characterized in that the orbital welding device (100, 101) comprises a welding head (104) which has a receptacle (106) for positioning a joining area (150) of two joining partners that are at least tubular in the joining area, in particular a fitting (152) and a pipe end (154), that the orbital welding device (100, 101) comprises an electrode drive (124) which is configured to move a welding electrode (126) in a circumferential direction around the receptacle (106), and that one of the first and second outputs (174, 176) of the welding power source (128) is electrically connected to the welding electrode (126) or an electrode holder for a welding electrode (126) for a welding operation, and the other of each of the first and second outputs (174, 176) is electrically connected to a contacting means (664) for contacting a joining partner.

22. Orbital welding device according to claim 20 or 21, characterized in that a control device (130, 198) is provided which is configured to control the orbital welding device (100, 101) in such a way that a weld seam is produced by means of the welding electrode (126) on two joining partners arranged in the receptacle (106) from a circumferentially extending chain of joining points (210).

23. Orbital welding device according to one of claims 20 to 22, characterized in that the orbital welding device (100, 101) comprises a hand-held device (102) which includes the welding head (104).

24. System (700) comprising an orbital welding device (100, 101) according to one of claims 20 to 23 and a fitting (152).

25. Orbital welding process, carried out with an orbital welding device (100, 101), in particular an orbital welding device according to one of claims 20 to 23, wherein the welding power source (128) of the orbital welding device (100, 101) is operated according to a method according to one of claims 15 to 19.

26. Orbital welding method according to claim 25, characterized in that two joining partners, at least in one joining area (150), are arranged relative to each other, in particular in an overlap joint, and that in the joining area (150) a chain of joining points (210) extending in the circumferential direction of the joining partners is generated, which connects the joining partners by a material bond.

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