Device and method for generating an ignition pulse for a welding apparatus, welding device

Abstract

Device and method for generating an ignition pulse for a welding apparatus. The device comprises an output terminal for connection to a hose package of the welding apparatus, a control device for providing a high-frequency signal at a high-frequency terminal, an inductive component arranged between the high-frequency terminal and the output terminal, as well as a first capacitor electrically coupled to at least one connection point of the inductive component. The control device is designed to adjust the frequency of the high-frequency signal, thereby adapting it to the respective resonance properties of a resonant circuit comprising the hose package of the welding apparatus. This enables improved, stable, and efficient ignition of arc and plasma welding apparatuses.

Description

[0001] Description

[0002] title

[0003] Device and method for generating an ignition pulse for a welding machine, welding device

[0004] Technical field

[0005] The present invention relates to a device and a method for generating an ignition pulse for a welding machine, in particular an arc or plasma welding machine. The present invention further relates to a welding machine with such a device for generating an ignition pulse.

[0006] background

[0007] High-frequency ignition devices are used in arc and plasma welding machines to initiate the welding arc by igniting an electrical spark between the electrode and the workpiece. A well-established method for generating a high-voltage pulse is superimposed ignition. In this process, a pulse-resistant capacitor is pre-charged to a high voltage and discharged into the primary winding of an ignition transformer via a switching element. The resulting high voltage ionizes the gas in the electrode area, enabling the ignition of the arc. A spark gap, a thyristor, or a saturable ignition choke are typically used as switching elements.

[0008] Although superimposed ignition is widely used in practice, this technology has some technical limitations. A key limitation lies in the short individual pulse length of the ignition pulse. The discharge of the capacitor results in a damped oscillation that decays rapidly and exhibits a high amplitude only for a brief period. Furthermore, the maximum pulse repetition rate is typically limited to about 10 kHz by the capacitor recharging and the reset circuitry of the switching elements. This prevents the generation of a continuously oscillating high-frequency waveform.

[0009] Another problem arises from the polarity of the ignition pulse. Since superimposed ignition generates a damped oscillation, the maximum peak value of the ignition voltage always occurs only with a specific polarity. For example, if the welding potential is negative while the ignition pulse has a positive polarity, this can lead to the ionized ignition gap not being maintained before a stable arc forms.

[0010] Additionally, the capacitance of the torch cable significantly influences the achievable ignition voltage. As the length increases, the capacitive load rises, requiring a larger proportion of the ignition pulse's energy to be used to recharge this capacitance. This results in a reduction of the energy transferred to the electrode tip and a significant decrease in ignition performance with longer torch cables.

[0011] The problems with conventional ignition methods are exemplified in Figure 8, which illustrates the temporal evolution of a typical ignition pulse according to the prior art. The depicted pulse begins with a positive voltage peak of approximately 12 kV, followed by a significantly weaker negative peak of only about -6 kV. The next positive half-wave already reaches an amplitude of only about 2 kV, which corresponds to about one-sixth of the initial value. Thus, the maximum ignition voltage is practically only available in one polarity direction, while pulses of the opposite polarity are already significantly attenuated. This asymmetrical and rapidly decaying signal behavior is characteristic of conventional superposition ignitions, in which a pre-charged pulse capacitor is discharged into the primary winding of a transformer.The rapid drop in amplitude within a few microseconds means that an effective ignition voltage is only available for a very short time.

[0012] Based on the aforementioned limitations of existing high-frequency ignition devices, the object of the present invention is to provide an improved ignition for arc and plasma welding equipment.

[0013] In particular, a method should be developed that generates a high-frequency signal whose amplitudes are uniform in both polarity directions and which experiences no significant attenuation. This enables reliable initiation of the welding arc regardless of the existing welding potential, thereby reducing the risk of premature channel breakage.

[0014] The proposed method and the associated apparatus are intended to enable broad applicability for various welding processes, with TIG welding machines in particular benefiting from its advantages. At the same time, the solution is designed to be easily integrated into existing equipment concepts to ensure flexible and practical implementation. Summary of the invention

[0015] The present invention provides a device and a method for generating an ignition pulse for a welding machine, as well as a welding device with the features of the independent claims. Further advantageous

[0016] The execution methods are the subject of the dependent claims.

[0017] In a first aspect, the invention provides a device for generating an ignition pulse for a welding machine. The device comprises an output terminal with a first and a second connection point, which are provided for connection to a hose assembly of the welding machine. A control device is configured to provide a high-frequency signal at a high-frequency terminal. An inductive component is arranged between the high-frequency terminal and the output terminal. The control device is designed to determine the resonant frequency of a resonant circuit with a hose assembly connected to the output terminal (i.e., a resonant circuit which is or comprises a hose assembly connected to the output terminal). Furthermore, the control device is designed to adjust the frequency of the provided high-frequency signal using the determined resonant frequency.

[0018] In a second aspect, the invention provides a welding device comprising a welding power source and a device according to the invention for generating an ignition pulse in accordance with the preceding aspect.

[0019] The welding device can be a plasma welding device or an arc welding device, in particular for example a tungsten inert gas (TIG) welding machine, a MIG / MAG welding machine or an electrode welding machine.

[0020] According to yet another aspect, the invention provides a method for generating an ignition pulse for a welding machine. First, a device for generating an ignition pulse according to the preceding first aspect is provided. Then, a resonant frequency of an oscillating circuit with a hose assembly connected to the output port is determined. Subsequently, the oscillating circuit is excited by applying a high-frequency signal to a hose assembly connected to the output port of the device (either as the oscillating circuit itself or as part of the oscillating circuit). The frequency of the high-frequency signal is set using the detected sensor signal.

[0021] The present invention is based on the finding that known high-frequency ignition devices in arc and plasma welding machines are limited in their ignition performance by the limited duration and attenuation of the ignition pulses. In particular, the capacitive load of the hose assembly leads to a significant voltage drop, which considerably reduces the ignition voltage at the electrode tip with increasing hose assembly length. Furthermore, it has been shown that conventional superimposed ignitions exhibit one-sided polarity, which in certain welding applications creates the risk of premature channel breakage and the failure to establish a stable arc.

[0022] It is therefore an idea of ​​the present invention to take this finding into account and to provide an improved ignition characteristic. For this purpose, a high-frequency ignition device is provided that supplies a high-frequency signal whose amplitudes are uniform in both polarity directions and which does not experience significant attenuation during the ignition phase. The high-frequency signal is fed into a resonant circuit that is coupled to the electrode via the hose assembly. In such a configuration, such a resonant circuit can be formed by utilizing the parasitic property of the hose assembly.

[0023] The hose assembly of a welding machine serves to guide various lines, including the power line to the electrode, as well as, if necessary, further control lines and, if required, a gas supply for the shielding gas.

[0024] In particular, the hose assembly exhibits capacitive and inductive properties that can change depending on its position and orientation in space. Since these parameters determine the oscillation behavior of a resonant circuit involved in the ignition, movement of the hose assembly can lead to a change in the resonant frequency. Additionally, power lines from other electrical components, such as robot cables, can also cause a change in the resonant frequency.

[0025] The control unit generates a high-frequency signal that serves to excite the downstream resonant circuit. This signal can, for example, be provided in the form of a rectangular signal to enable excitation of the resonant circuit at the desired frequency.

[0026] The resonant circuit includes, among other things, the hose assembly and other electrical components of the device. The capacitive properties of the hose assembly contribute significantly to the oscillation behavior. The frequency of the high-frequency signal can be selected relative to a resonant frequency of a resonant circuit, which in particular includes the hose assembly. This frequency can be chosen so that it matches the resonant frequency of the resonant circuit or deviates slightly from it. In particular, the frequency can be up to 1.5 times, 2 times, 3 times, or 4 times the resonant frequency, or set to another integer multiple of the resonant frequency. It is also possible to set the frequency to a fraction of the resonant frequency, for example, down to half, a third, or a quarter of the resonant frequency.By selecting a suitable frequency, the oscillation behavior of the connected components can be used in a targeted manner to enable effective excitation and thus reliable ignition.

[0027] The resonant frequency of the resonant circuit can be determined or provided in various ways. For example, it can be determined by measuring the electrical behavior during excitation. Alternatively or additionally, it is possible to determine and store characteristic properties of the connected hose assembly or the entire resonant circuit in advance, so that the control unit can select a suitable frequency for the high-frequency signal based on this pre-determined information.

[0028] In one embodiment, a first capacitor is provided. This first capacitor is electrically coupled to at least one connection point of the inductive component. Together with the parasitic capacitances of the hose assembly, it forms part of the resonant circuit. This allows the resonance characteristics of the device to be specifically adjusted, particularly with regard to the achievable resonant frequency.

[0029] In another embodiment, the device includes a measuring device. This measuring device can, for example, be arranged between the high-frequency connection of the control unit and the output connection. This measuring device is advantageously designed to detect the temporal profile of at least one electrical parameter, such as voltage or current, in the resonant circuit and to provide a corresponding sensor signal. The measuring device detects electrical parameters of the system and provides a sensor signal that is used by the control unit to adaptively adjust the frequency of the high-frequency signal. This ensures that the ignition voltage is maintained regardless of the length of the torch cable assembly and enables reliable arc ignition.

[0030] The measuring device detects an electrical parameter of the ignition device, which is used to adjust the high-frequency signal. This is typically a current or voltage measurement, but other physical quantities are also conceivable in principle.

[0031] The measuring device can be positioned at various locations within the apparatus. One possibility is to place it near the output terminal, for example, between the inductive component and one of the output terminal's connection points. In this arrangement, the measurement is taken close to the torch cable assembly, so that the recorded values ​​reflect the electrical conditions at the ignition path as accurately as possible. This allows the frequency control of the high-frequency signal to be adapted to the actual conditions at the electrode tip.

[0032] Alternatively, the measuring device can be positioned between the control unit and the inductive component. In this position, lower electrical voltages are typically expected, which can reduce the requirements for the measuring electronics. In particular, such an arrangement could eliminate the need for complex protective measures or galvanic isolation.

[0033] The signal detected by the measuring device is provided as a sensor signal and fed to the control unit for further processing. This allows the frequency of the high-frequency signal to be precisely adjusted to enable reliable and efficient ignition.

[0034] The control unit can evaluate this sensor signal from the measuring device to determine the resonant frequency of the resonant circuit with the connected hose assembly. Based on this, a targeted frequency adjustment can then be performed to optimally adapt the high-frequency signal to the prevailing conditions.

[0035] In another embodiment, the control device is designed to determine the resonant frequency of the resonant circuit with a hose assembly connected to the output terminal, using a previously determined characteristic parameter for the hose assembly. Such characteristic parameters may have been determined, for example, during a prior measurement, such as by laboratory measurements of the resonant circuit with the connected hose assembly, or by isolated determination of the parasitic properties of the hose assembly itself, in particular its parasitic inductance and capacitance. The parameters determined in this way can either directly specify the resonant frequency of the resonant circuit with the hose assembly, or they allow for a computational determination of the resonant frequency, which is then used to set the frequency of the high-frequency signal.

[0036] In another embodiment, the device includes a storage unit designed to store and provide a relationship between hose packages connectable to the output port and at least one previously determined characteristic parameter for each hose package. The selection of the data to be used from the storage unit can be carried out in two ways: Firstly, the connected hose package can be automatically identified, for example, based on its length, type, or other identifying characteristics. Alternatively, a user can manually connect a hose package and then enter the relevant information via a user interface. In both cases, the characteristic data applicable to the respective hose package are automatically read from the storage unit and used to determine the frequency of the high-frequency signal to be applied.

[0037] In another embodiment, the device includes a second capacitor arranged between a connection point of the high-frequency terminal and the inductive component. This arrangement allows the second capacitor to help block DC components in the excitation of the resonant circuit, so that essentially only the AC components of the high-frequency signal are used to drive the resonant circuit.

[0038] In another embodiment, the inductive component includes a transformer. The primary side of the transformer is electrically coupled to the high-frequency connection of the control device, while the secondary side is connected to the output terminal.

[0039] This arrangement achieves galvanic isolation between the drive unit and the cable assembly, which can have a beneficial effect on the electrical insulation of the components. Furthermore, the transformer allows for adjustment of the high-frequency signal voltage by selecting a suitable turns ratio. For example, the drive circuit can generate a signal with a comparatively low voltage, which is then converted to a higher voltage by the transformer to ensure efficient excitation of the resonant circuit.

[0040] In another embodiment, the inductive component comprises a first coil which is electrically coupled at a first connection point to a first connection point of the high-frequency terminal of the control device and at a second connection point to a second connection point of the output terminal. This arrangement can be used to form a resonant circuit according to the invention without requiring a galvanically isolating transformer.

[0041] In a further embodiment of this design, a second coil is provided, which is electrically connected at one connection point to the first connection point of the first coil and at another connection point to the second connection point of the high-frequency terminal. Thus, the second coil can also be connected at its second connection point, which is connected to the second connection point of the high-frequency terminal, to the first connection point of the output terminal. This second coil can, in particular, be an air-core coil.

[0042] In another embodiment, the control device is designed to provide the high-frequency signal in the form of pulses. These pulses can have a predetermined pulse duration and / or a defined pulse amplitude, thus allowing targeted control of the signal characteristics.

[0043] In a further embodiment of this variant, the control device can generate a sequence of pulses with predetermined time intervals. Such a pulse sequence can form a periodic pattern over the output time, which determines the temporal behavior of the high-frequency signal.

[0044] By selectively choosing the pulse intervals, different ignition characteristics can be achieved, for example to adapt to different welding conditions or to influence the energy distribution within the ignition sequence.

[0045] In another embodiment, the control device is designed to determine the ignition energy emitted during a pulse and, based on this determination, to adjust the pulse duration, pulse amplitude and / or the time interval between pulses.

[0046] This regulation ensures that the ignition energy output remains limited within a specified time interval. This allows for the targeted delivery of high energy in short pulses, while no further energy is emitted during the intervening phases. In this way, the ignition process can be carried out with a high power output without exceeding defined limits, which can be particularly important for personal safety.

[0047] In another embodiment, the high-frequency component of the output voltage provided at the output terminal has an at least approximately continuous sinusoidal signal shape or is designed as a pulse with an at least approximately continuous sinusoidal signal shape.

[0048] With this type of signal waveform, the amplitude remains as constant as possible over the duration of the pulse, without significant attenuation. This contributes to the fact that the amplitudes in both polarity directions are approximately equal, so that no particular polarity is favored.

[0049] In another embodiment, the control device is designed to monitor the waveform of the high-frequency component of the output voltage provided at the output terminal. If the attenuation of this high-frequency component exceeds a predetermined threshold, the provision of the high-frequency signal is terminated.

[0050] This monitoring allows for a response to unexpected changes in the electrical characteristics of the resonant circuit. In particular, strong damping can indicate that the load resistance on the secondary side has dropped significantly, for example, due to unintentional contact with a human body. In such a case, the high-frequency signal is switched off to minimize the energy transferred to the body without affecting normal ignition performance during regular operation.

[0051] In another embodiment, the high-frequency signal has a frequency of at least 10 kilohertz. Preferably, the frequency lies in a range between 300 kilohertz and 3 megahertz.

[0052] The choice of frequency depends, among other things, on the resonance characteristics of the resonant circuit, which result from the combination of the cable assembly, ignition transformer, and resonant capacitor. In many applications, the resonant frequency is typically in the range of 300 kilohertz to 1.3 megahertz. Higher frequencies, especially up to several megahertz, are also achievable and, under certain conditions, allow for a more compact design of the circuit components.

[0053] In another embodiment, the control device includes a power supply circuit designed to set a modulatable supply voltage for providing the high-frequency signal.

[0054] By modulating the supply voltage, the amplitude of the high-frequency signal can be precisely controlled. Particularly in a drive circuit implemented with one or more half-bridges, a DC input voltage can be converted into an AC voltage according to the clock rate of the high-frequency signal. Adjusting the supply voltage allows for flexible control of the output amplitude and adaptation to different operating conditions. The supply voltage modulation can, for example, be implemented as a ramp curve, enabling a controlled change in the output amplitude over time.

[0055] The above embodiments and further developments can be combined with one another as appropriate, provided this is technically feasible. Further embodiments, further developments, and implementations of the invention also include combinations of features not explicitly mentioned above or below in connection with the exemplary embodiments.

[0056] In particular, features described in connection with a device can also be transferred to corresponding process aspects and vice versa. Furthermore, the person skilled in the art will recognize that individual aspects of the invention can be used as improvements or additions to the respective basic forms of the invention.

[0057] Brief description of the drawings

[0058] Further features and advantages of the invention are explained below with reference to the figures.

[0059] This shows:

[0060] Figure 1 shows a schematic overview of a welding device with a device for generating an ignition pulse.

[0061] Figure 2 shows a schematic diagram of a device for generating an ignition pulse according to one embodiment.

[0062] Figure 3 shows an exemplary comparison of the output voltage curve during ignition according to the present invention and during a conventional ignition pulse; Figure 4 shows a schematic diagram of a welding device according to a further embodiment.

[0063] Figure 5 shows a schematic diagram of a welding device according to a further embodiment with parallel coupling of the high-frequency signal.

[0064] Figure 6 shows a schematic diagram of a welding device according to a further embodiment with a directly fed topology.

[0065] Figure 7 shows a flow diagram of a method for generating an ignition pulse as it may form the basis of an implementation; and

[0066] Figure 8 schematically shows the temporal progression of a typical ignition pulse according to the state of the art.

[0067] Preferred embodiments of the invention are explained in more detail below with reference to the figures. The examples shown serve for illustration and are not to be understood as limiting. In particular, individual features of the described embodiments can be combined with one another or replaced by functionally equivalent features, provided this is technically feasible. Identical reference numerals denote identical or similar components.

[0068] Description of execution forms

[0069] Figure 1 shows a schematic overview diagram of a welding device according to one embodiment of the invention. The welding device comprises a welding unit 1, to which a hose assembly 2 can be connected via the output port 12. A welding torch 3 is arranged at the opposite end of the hose assembly 2.

[0070] The welding machine 1 can be an arc welding machine or a plasma welding machine, for example a TIG welding machine or a MIG / MAG welding machine. The invention is not limited to a specific type of welding machine, but can in principle be used in various welding processes in which a high-frequency ignition pulse can be used for arc ignition.

[0071] The welding machine 1 comprises a welding power source 11, the basic structure of which can be considered known and is therefore not described in detail. The welding power source 11 provides the welding current between a positive and a negative terminal at the output terminal 12, where the output terminal 12 may, for example, be designed as or include welding sockets.

[0072] Furthermore, the welding machine 1 includes a device 10 for generating an ignition pulse (or: ignition device). The ignition pulse serves to ignite an arc at the welding torch 3 at the beginning of a welding process. Once the arc has stabilized, it can be maintained by the electrical energy supplied by the welding power source 11.

[0073] In the schematic representation of Figure 1, the device 10 is arranged parallel to the welding power source 11. However, this representation serves only for clarity and does not limit the invention.

[0074] In another preferred embodiment, the device 10 is connected in series to one of the two connections between the welding power source 11 and the output terminal 12. Furthermore, the following descriptions apply to both variants of the arrangement – ​​series and parallel – as far as applicable.

[0075] The hose assembly 2 includes, in addition to the welding current cable, possibly other cables, such as control cables and / or a gas supply for the shielding gas. The hose assembly 2 exhibits parasitic electrical properties, in particular a parasitic capacitance Cx and a parasitic inductance Lx. These properties depend on both the length of the hose assembly 2 and its position in space, and can change during operation, for example, due to movement of the hose assembly 2.

[0076] Figure 2 shows a schematic circuit diagram of a device 10 for generating an ignition pulse according to one embodiment of the invention. The device 10 comprises a control unit 110, which provides a high-frequency signal via a high-frequency connection 111. This high-frequency signal is fed to the primary side of a transformer 120, which serves to generate the high voltage required for ignition.

[0077] Transformer 120 has a magnetizing inductance Lm and a leakage inductance Ls. The secondary side of transformer 120 is coupled to a resonant circuit comprising the leakage inductance Ls of transformer 120, a first capacitor Cr, the parasitic inductance Lx of hose assembly 2, and the parasitic capacitance Cx of hose assembly 2. In this embodiment, the first capacitor Cr is located between the two connection points. This resonant circuit forms a resonant structure whose frequency depends on the length and position of hose assembly 2. The first capacitor Cr is optional and can be omitted if the parasitic capacitances of hose assembly 2 alone satisfy the resonance conditions. However, the use of the first capacitor Cr is advantageous because it allows for targeted manipulation of the resonance characteristics and, in particular, tuning of the achievable resonant frequency.

[0078] To ensure efficient excitation of this resonant circuit, the control unit 110 is designed to adapt the high-frequency signal to the current resonant frequency of the system. For this purpose, a measuring device 130 is provided, which is located here on the primary side of the transformer 120 between the high-frequency terminal 111 and the transformer 120. The measuring device 130 detects the signal waveform of an electrical parameter, for example, current or voltage, and provides a sensor signal. Based on this sensor signal, the control unit 110 can dynamically adjust the frequency of the high-frequency signal to ensure optimal energy transfer to the resonant circuit.

[0079] Alternatively or additionally to the metrological acquisition of a sensor signal, the frequency of the high-frequency signal can also be set based on previously determined properties of the resonant circuit. Such an approach can be particularly advantageous if the characteristics of the hose assembly used are already known or have been determined beforehand, for example, as part of a laboratory measurement.

[0080] For this purpose, the resonant frequency of the resonant circuit with a specific hose assembly can be fully determined and stored for later applications. Alternatively, it is also possible to determine only individual characteristic parameters of the hose assembly, such as the parasitic capacitance or inductance, and store them in a suitable relationship for the respective hose assembly. From these previously determined parameters, the expected resonant frequency of the resonant circuit can be derived mathematically.

[0081] The relevant parameters for each connected hose assembly can be stored in a memory unit, which contains a data set with different hose assemblies and their characteristic properties. The control unit can then adjust the excitation frequency of the high-frequency signal based on this data.

[0082] This allows the connected hose package to be automatically identified – for example, via an electronic marking or a coded connector – so that the associated data can be automatically read from the memory and used.

[0083] Alternatively, the user can manually specify which hose package is connected via a user interface, for example by selecting it from a list or by entering specific characteristics such as type, length, or manufacturer information. In this case, too, the stored parameters can then be accessed automatically and the frequency of the high-frequency signal adjusted accordingly.

[0084] The use of previously acquired data enables particularly efficient excitation of the resonant circuit, even without complex measurement feedback during operation. This can be especially advantageous in systems where the number and type of connected hose packages are manageable, or where they are frequently used in a known configuration.

[0085] To block DC voltage components, a second capacitor Cb is provided as a blocking capacitor, which is arranged between the high-frequency connection 111 and the primary side of the transformer 120.

[0086] The control unit 110 is designed to provide a high-frequency signal at a desired frequency. For this purpose, it can, for example, comprise one or more half-bridges that generate a rectangular alternating voltage from an input DC voltage. The input voltage of the control unit 110 can be modulated so that a rising voltage is provided at the beginning of the excitation. This makes it possible to precisely adjust the amplitude of the high-frequency signal, for example, via a ramp curve or another modulation form.

[0087] The high-frequency signal preferably has a frequency of at least 10 kHz. In particular, the frequency can be in a range between 300 kHz and 3 MHz. The choice of frequency depends on the resonance characteristics of the resonant circuit, which is defined by the hose assembly 2, the transformer 120, and the first capacitor Gr.

[0088] Typically, the resonant frequency lies in the range of 300 kHz to 1.3 MHz, depending on the specific components and the electrical configuration of the device 10. However, using modern semiconductor technologies, such as SiC MOSFETs or GaN FETs, higher frequencies up to the range of several megahertz can also be achieved. Under certain conditions, this allows for a more compact design of the circuit components, since smaller inductances and capacitances are required for the desired resonant excitation with increasing frequency.

[0089] The excitation and feedback from the measuring device 130 excites the resonant circuit on the secondary side of the transformer 120. The resonant circuit comprises the leakage inductance Ls of the transformer 120, the first capacitor Cr, the parasitic inductance Lx of the hose assembly 2, and the parasitic capacitance Cx of the hose assembly 2.

[0090] The control unit 110 can detect the resonant frequency of this resonant circuit and adjust the excitation frequency accordingly. In many cases, the excitation is performed at a frequency slightly above the resonant frequency to account for the switching losses of the semiconductor switches. This frequency can be up to four times the resonant frequency or set to integer multiples of the resonant frequency. It is also possible to set the excitation frequency to a fraction of the resonant frequency, for example, down to a quarter of the resonant frequency.

[0091] Figure 3 shows an exemplary comparison of two ignition pulses to illustrate the signal waveforms of conventional and inventive systems. Both diagrams show a voltage profile over an identical time period of 50 microseconds.

[0092] The diagram above shows an ignition pulse as it can be provided according to one embodiment of the present invention. In the example shown, the output voltage initially rises to a maximum amplitude of ±12 kV within a rise time of approximately 20 to 25 microseconds. Subsequently, the voltage remains approximately constant at this level, with both the positive and negative half-waves being equally pronounced. This symmetrical and largely attenuation-free signal waveform enables uniform ignition regardless of the polarity and provides the high voltage over a longer period.

[0093] For comparison, the lower diagram shows a typical ignition pulse as generated by a conventional superimposed ignition system. The voltage curve corresponds to the pulse profile already described with reference to Figure 8: After an initial positive voltage peak of approximately 12 kV, a weakened negative half-wave of around -6 kV follows, and then a significantly lower second positive half-wave of only about 2 kV. The pulse decays rapidly within a few microseconds, so that the maximum ignition voltage is present only in one polarity direction and only for a very short period.

[0094] The comparison illustrates the difference between the dampened, asymmetrical behavior of conventional ignition pulses and the smooth, largely constant course of the signal shape according to the invention.

[0095] To ensure safety during operation, the measuring device 130 is designed to monitor the high-frequency component of the output voltage U. An unexpected change in the electrical characteristics of the resonant circuit may indicate unintentional contact with a person. In such a case, the load resistance on the secondary side of the transformer 120 drops to a few kΩ (e.g., 0.5 kΩ), resulting in significant attenuation of the high-frequency signal. If such attenuation is detected and exceeds a predetermined threshold, the control device 110 immediately terminates the supply of the high-frequency signal.

[0096] This rapid shutdown not only minimizes the energy released but can also prevent a person from being startled by contact. This is particularly important during assembly work with a welding machine, as a sudden start could lead to uncontrolled movements and potentially dangerous situations. Although the energy stored in the resonant capacitor Cr and the parasitic capacitance of the hose assembly Cx is still released after shutdown, the total amount of energy released is significantly reduced. This reduces the strain on the affected person and further improves personal safety.

[0097] The high-frequency signal for the ignition pulse can be output in different forms. In one variant, the signal is provided as a continuous high-frequency signal, with the control unit 110 adjusting the frequency depending on the resonant frequency of the resonant circuit.

[0098] Alternatively, the high-frequency signal can be output in the form of pulses. The pulse duration, pulse amplitude, and time interval between pulses can all be varied. This pulse output offers several advantages, particularly with regard to compliance with safety regulations. By precisely designing the pulse sequence, a high amount of energy can be delivered within a single pulse, while the energy averaged over time remains reduced. This enables an effective, high-power ignition process without exceeding permissible energy output limits. This is especially advantageous with regard to personal safety.

[0099] Figure 4 shows a schematic representation of a welding device with a device 10 for generating an ignition pulse according to a further embodiment.

[0100] In contrast to the previously described embodiment, in this variant the measuring device 130 is provided on the secondary side of the transformer 120. It is arranged between the transformer 120 and a connection point 12b of the output terminal 12.

[0101] Furthermore, Figure 4 shows the connection of the device 10 together with the welding power source 11, with both feeding into the output terminal 12. The welding current from the welding power source 11 is supplied via a transformer 220 and rectified by means of diodes D1 and D2.

[0102] In this embodiment, the first capacitor Gr is arranged in parallel to the secondary side of the transformer 120 of the device 10. One terminal of the first capacitor Gr is connected to terminal 12b of the output terminal 12, while the other terminal 12a is coupled to a terminal on the secondary side of the transformer 220 of the welding power source 11. Figure 5 shows an alternative embodiment of the welding device in which the coupling of the high-frequency signal is not serial to the output of the welding current, but parallel to it.

[0103] In this configuration, the welding power source 11 provides the welding current at the output terminal 12. In parallel, the high-frequency signal is coupled in via the transformer 120 and the first capacitor Cr on the secondary side of the transformer 120. This arrangement thus differs from the previously described variants in which the high-frequency signal was fed in series with the welding power source 11.

[0104] Additionally, a blocking coil 230 is provided between the center terminal of the secondary side of the transformer 220 of the welding power source 11 and the corresponding terminal of the output terminal 12. The ignition voltage drops across this blocking coil 230. Otherwise, the welding power source could short-circuit the ignition voltage, and a high voltage could not build up.

[0105] In this embodiment, the measuring device 130 is provided on the primary side of the transformer 120. However, an arrangement on the secondary side would also be possible in principle.

[0106] Furthermore, in this embodiment, a coupling capacitor Ck is provided, which can be arranged between a terminal of the first capacitor Cr or a terminal of the secondary side of the transformer 120 and a corresponding terminal point of the output terminal 12. The coupling capacitor Ck blocks low-frequency components and DC voltage components of the TI-

[0107] Welding power source 11, while it allows the high-frequency ignition signal to pass. This prevents the ignition transformer 120 from short-circuiting low-frequency voltages or DC voltages of the welding power source and thus impairing the welding potential.

[0108] Figure 6 shows an alternative embodiment of the welding device in which the high-frequency signal is directly coupled to the output terminal 12 without a galvanically isolating transformer 120.

[0109] In this variant, the inductors Li and Lr can, for example, be implemented as air coils. The square wave signal generated by the control unit 110 is applied in parallel to the air coil Li via the blocking capacitor Cb. The air coil Li is required to conduct the welding current through the topology.

[0110] The series resonant circuit consists of the air-core inductor Lr, the first capacitor Cr, and the parasitic components of the tube assembly 2, in particular the inductance Lx and the capacitance Cx. The inductance Li should be dimensioned to be a few microhenries (pH) (for example, between 0.5 and 9 microhenries), as otherwise the reactance will be too low and the current flow from the drive unit 110 could increase uncontrollably.

[0111] By choosing a suitable resonance and switching frequency, air coils can be implemented efficiently, while their impact on the welding process remains minimal.

[0112] Additionally, the parallel feed to the inductor Li can also be achieved via a small ferrite transformer, allowing the bridge voltage to be freely selected. However, it must be taken into account that in this case the inductor Li becomes part of the series resonant circuit, and correspondingly high voltages can occur in parallel with Li.

[0113] The method described below can include any steps suitable for realizing the full connection with the implementation forms described in the devices. Furthermore, the devices described above can be modified and supplemented as needed to combine the various implementation forms, where appropriate, or to implement the subsequent method steps.

[0114] Figure 7 shows a flow diagram of a method for generating an ignition pulse for a welding machine 1. In a first step S1, a device 10 is provided, which is constructed according to one of the previous embodiments. This device comprises a control device 110, a measuring device 130, and an inductive component, for example, a transformer 120 or a coil arrangement.

[0115] After the device 10 has been provided, in a next step S2 a resonant frequency of the resonant circuit with the hose assembly 2 enclosed at the output port 12 is determined. As already explained above in connection with the device 10, this determination of the resonant frequency can advantageously be carried out using sensor signals from a measuring device 130. Additionally or alternatively, the determination of the resonant frequency can also be carried out using previously stored data, for example, a resonant frequency previously determined for a connected hose assembly 2 or specific parameters for such a hose assembly 2.

[0116] In step S3, a high-frequency signal can then be generated by the control device 110, which is output via the high-frequency connection 111. This signal excites a resonant circuit consisting of the leakage inductance Ls of the transformer 120, the first capacitor Cr, and the parasitic properties of the hose assembly 2, in particular the parasitic inductance Lx and the parasitic capacitance Cx.

[0117] During operation, the measuring device 130 can optionally capture a sensor signal in a further step S4, which describes the signal profile of an electrical parameter, for example the current or voltage.

[0118] This sensor signal provides information about the current resonance characteristics of the resonant circuit, which can change due to changes in the length or position of the hose package 2.

[0119] In this case, the frequency of the high-frequency signal can be adjusted by the control unit 110 based on the sensor signal acquired by the measuring unit 130. This adjustment is made in real time to ensure optimal energy transfer. The high-frequency signal is provided at a frequency suitable for ignition, which depends on…

[0120] The design may lie slightly above the resonance frequency, although other control strategies are also possible.

[0121] Furthermore, it is optionally possible to jump back to step S2 after generating an ignition pulse and generate another ignition pulse until a successful ignition has occurred.

[0122] In summary, the present invention provides a device and a method for generating an ignition pulse for a welding machine. The device comprises an output port for connection to a welding machine hose assembly, a control unit for providing a high-frequency signal at a high-frequency port, an inductive component arranged between the high-frequency port and the output port, and a first capacitor electrically coupled to at least one connection point of the inductive component. The control unit is designed to adjust the frequency of the high-frequency signal, thereby adapting it to the respective resonance characteristics of a resonant circuit with the welding machine hose assembly. This enables improved, stable, and efficient ignition of arc and plasma welding machines.

Claims

Patent claims 1. Device ( 10) for generating an ignition pulse for a welding machine, comprising: an output port ( 12 ) with a first connection point and a second connection point, wherein the output port ( 12 ) is configured to be connected at the first connection point and the second connection point to a hose package (2 ) of the welding machine; a control device ( 110) which is configured to provide a high-frequency signal at a high-frequency connection ( 111 ) of the control device ( 110); an inductive component ( 120; Li, Lr) , which is arranged between the high-frequency terminal ( 111 ) of the control device ( 110) and the output terminal ( 12 ); wherein the control device ( 110) is designed to determine a resonant frequency of a resonant circuit with a hose package (2 ) connected to the output port ( 12 ) and to set a frequency of the high frequency signal provided by the control device ( 110) using the determined resonant frequency .

2. Device according to claim 1, comprising a first capacitor (Cr) which is electrically coupled to at least one connection point of the inductive component ( 120; Li, Lr .

3. Device ( 10) according to claim 1 or 2, with a measuring device ( 130) which is arranged between the high-frequency connection ( 111 ) and the output connection ( 12 ) and which is designed to detect a signal waveform of at least one electrical parameter and to provide a sensor signal corresponding to the detected signal waveform; wherein the control device ( 110) is designed to determine the resonant frequency of the resonant circuit with the hose package (2 ) connected to the output port ( 12 ) using the sensor signal provided by the measuring device ( 130 ).

4. Device ( 10) according to one of claims 1 to 3, wherein the control device ( 110) is designed to determine the resonant frequency of the resonant circuit with a hose package (2 ) connected to the output port ( 12 ) using a previously determined characteristic parameter for the connected hose package (2 ).

5. Device ( 10) according to claim 4, with a storage device designed to store and provide a relationship between hose packages (2) connectable to the output port ( 12 ) and at least one previously determined characteristic parameter for the respective hose package (2 ).

6. Device ( 10) according to one of claims 1 to 5, with a second capacitor (Cb) which is arranged between a connection point of the high frequency connection ( 111 ) and the inductive component ( 120; Li, Lr ).

7. Device ( 10) according to one of claims 1 to 6, wherein the inductive component comprises a transformer ( 120), and wherein a primary side of the transformer ( 120) is electrically coupled to the high-frequency connection ( 111 ) of the control device ( 110) and a secondary side of the transformer ( 120) is electrically coupled to the output connection ( 12 ).

8. Device ( 10) according to one of claims 1 to 6, wherein the inductive component comprises a first coil (Lr) which is electrically coupled at a first connection point to a first connection point of the high frequency connection ( 111 ) of the control device ( 110) and is electrically coupled at a second connection point to a second connection point of the output connection ( 12 ).

9. Device ( 10) according to claim 8, with a second coil (Li) which is electrically connected at a first connection point to the first connection point of the first coil (Lr) and is electrically coupled at a second connection point to a second connection point of the high frequency terminal ( 111 ) and to a first connection point ( 12b) of the output terminal ( 12 ).

10. Device ( 10) according to any one of claims 1 to 8, wherein the control device ( 110) is designed to provide the high-frequency signal in the form of pulses with a predetermined pulse duration and / or pulse amplitude.

11. Device ( 10) according to claim 10, wherein the control device ( 110) is designed to provide a sequence of pulses at predetermined time intervals.

12. Device ( 10) according to claim 10 or 11, wherein the control device ( 110) is designed to determine an ignition energy delivered during a pulse and to adjust the pulse duration and / or the pulse amplitude and / or the time interval between the pulses using the determined ignition energy.

13. Device ( 10) according to one of claims 1 to 12, wherein a high-frequency component of an output voltage provided at the output terminal ( 12 ) has an at least approximately continuous sinusoidal signal shape or a pulse with an at least approximately continuous sinusoidal signal shape .

14. Device ( 10) according to any one of claims 1 to 13, wherein the control device ( 110) is designed to monitor the course of the high-frequency component of the output voltage provided at the output terminal ( 12 ) and to terminate the provision of the high-frequency signal if attenuation of the high-frequency component of the output voltage provided at the output terminal ( 12 ) exceeds a predetermined threshold.

15. Device ( 10) according to any one of claims 1 to 14, wherein the high-frequency signal has a frequency of at least 10 kilohertz, preferably a frequency in a range between 300 kilohertz and 3 megahertz .

16. Device ( 10) according to any one of claims 1 to 15, wherein the control device ( 110) comprises a power supply circuit designed to set a modulatable supply voltage for providing the high frequency signal.

17. Welding apparatus, with: a welding power source ( 11 ); and a device ( 10) for generating an ignition pulse according to any one of claims 1 to 14.

18. Welding device according to claim 17, wherein the welding device comprises a plasma welding device or an arc welding device, in particular a tungsten inert gas TIG welding machine, a MIG / MAG welding machine or an electrode welding machine .

19. Method for generating an ignition pulse for a welding machine, comprising the steps: Providing (Sl ) a device ( 10) for generating an ignition pulse according to any one of claims 1 to 13; Determine (S2 ) a resonant frequency of a resonant circuit with a hose package (2 ) connected to the output port ( 12 ); Excitation (S3) of the resonant circuit with a high-frequency signal, wherein the high-frequency signal is set using the determined resonant frequency of the resonant circuit.

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